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Suction stress, the part of effective stress induced by soil–water interaction, is the source for the intrinsic cohesion of fine-grained soil slurries. Here, the previous unified effective stress equation is generalized to extend the suction stress variation from the liquid state to the oven-dry state, yielding an augmented closed-form equation. This equation includes a new term, named slurry adsorptive suction stress, to incorporate the adsorptive mechanism of soil slurries at the liquid state. This adsorption mechanism involves the interparticle van der Waals attraction, face-to-edge attraction, and electrical double-layer repulsion when soils are in the liquid state. The proposed equation is validated with a wide array of 12 fine-grained soils' shrinkage curves, modulus, and suction stress data measured by the drying cake test. It is demonstrated that the proposed equation can excellently capture the experimental data across all saturations. Furthermore, the practical implications of the proposed model are illustrated via its relevance to rheological properties of soil slurries and correlations with both liquid limit and plastic limit. [ABSTRACT FROM AUTHOR]

As an effective reinforcement technology for seepage prevention, penetration grouting has been widely used in geotechnical and underground engineering. Because grouting is a hidden project, the extent of slurry spread is often estimated theoretically and through experience. Therefore, it is important to understand the diffusion pattern and scope of penetration grouting in reinforcement engineering. Based on the generalized Darcy's law, a penetration grouting model considering the gravity and the time-varying nature of the slurry viscosity is proposed in this study. Its validity and effectiveness are verified through a comparison with existing penetration grouting tests. Based on the established penetration grouting model, the effects of the grouting pressure, permeability coefficient, water–cement ratio, and other factors on penetration grouting are analyzed. The penetration and diffusion process of a Bingham fluid considering gravity and time-variable slurry viscosity is computationally simulated using a finite-element software. The research results show that the proposed penetration grouting model is more accurate than the traditional one that does not consider the two aforementioned factors, and its results are more in line with the experimental ones. The rate of error calculated from the experimental value is about 11%. The diffusion radius of the slurry increases with increasing grouting pressure, permeability coefficient, and water–cement ratio, and decreases with increasing groundwater pressure. With the elapse of the grouting time, the increase rate of the diffusion radius exhibits a trend of increasing first and then decreasing and tending to level off. These research results can provide certain theoretical support for penetration grouting research in geotechnical and underground engineering. [ABSTRACT FROM AUTHOR]

Borehole wall stability is the key to the shield tunnel and horizontal directional drilling (HDD) under a sand-pebble layer. Borehole instability will lead to the collapse of the upper ground and damage to adjacent structures. To improve the stability of transportation in highly permeable formations, it is suggested that quartz sand be added to the silicate membrane. Here, different particle sizes (40, 70, 120 mesh) and contents (1%, 2%, 3%, and 4%) of quartz sand were applied to investigate the influence of quartz sand on the properties of silicate slurry and filter cake performance by analyzing the rheological properties, fluid loss, and filter cake properties. The results show that when the particle size is 120 mesh and the content is 2% in the membrane slurry, the quartz sand effectively promotes the filter cake performance. Moreover, the spatial structure formed in the slurry is continuous, and the viscosity, static shear force, dynamic shear force, and flow index of the slurry are within an appropriate range, indicating that silicate slurry with 120 mesh and 2% content quartz sand can make the slurry perform well in the sand-pebble layer. This formulation facilitates the effective formation of the filter cake, reduces fluid loss volume, and maintains borehole stability. [ABSTRACT FROM AUTHOR]

The geotechnical centrifuge is an efficient alternative to the slurry consolidometer and settling columns for expedited testing of mine tailings and dredged clay slurries, while accurately reproducing the field stress conditions. Existing numerical models for centrifuge consolidation use piecewise linear and finite-difference methods, and are computationally expensive. This study introduces, for the first time, a finite-element formulation for centrifuge finite-strain consolidation. The proposed model accounts for the nonlinearity induced by the hydraulic conductivity, soil compressibility, and acceleration factor variation along the depth of the centrifuge test specimen. The model incorporates the modified Newton–Raphson method and an implicit time integration technique, leading to a significant reduction in the computational expense. The settlement rate curves generated by the proposed model are validated with corresponding experimental data from the literature studies. The computational cost of the proposed model and existing finite-difference based models are compared for centrifuge and normal gravity consolidation testing conditions. Finally, a parametric analysis is presented to show the influence of various parameters on the functional time steps chosen for the finite-element simulations. The model demonstrates computational robustness and is instrumental for parameter estimation through inverse analysis, and prediction of in-field finite-strain consolidation behavior of slurry wastes. [ABSTRACT FROM AUTHOR]

To solve the problem of the proportional design of cement concrete prepared by using manufactured sand instead of river sand, a new method of manufactured sand concrete mix design was proposed with the dense packing of coarse and fine aggregate. Compared with the original sieving method, the stone powder in the manufactured sand can be regarded as cementitious materials for slurry. With the proposed mix design method, there is no need to separate from the manufactured sand. This dense packing method considers the actual situation that both the manufactured sand and coarse aggregate are mechanically prepared, and all the aggregates can be unified in proportion. The composition ratio of aggregate with particle size greater than 0.075 mm is designed by the maximum density theory, and the rest of the part (below 0.075 mm) is treated as a cementitious material. As a parameter of the maximum density theory, the Fuller index of 0.45 was verified when the calculation values agreed well with the test results. With the proposed mix ratio design method, the different grades C30, C40, and C50 of manufactured sand concrete were designed. Furthermore, the properties such as workability and mechanical properties for the designed manufactured sand concrete were investigated to determine the applicability of the proposed mix design method. The test results show that the workability, uniformity, and strength of the manufactured sand concrete were better than the original mix ratio design method, which verifies the operability and reasonableness of the proposed mix ratio design method. [ABSTRACT FROM AUTHOR]

To address the engineering problem of wall collapse and destabilization during the construction of the slurry trench wall, the stability of the slurry trench wall under the condition of three-dimensional (3D) unsaturated stable seepage is studied using the upper limit analysis method and in combination with the three-dimensional rotating failure mechanism. The expression of the factor of safety (FS) for the unsaturated soil slurry trench was deduced by the gravity increase method. Additionally, a genetic algorithm was used to search for the minimum FS and the critical slip surface, and the obtained results were compared and validated with existing literature results. The effects of relevant parameters on the stability of the slurry trench under the condition of unsaturated seepage were analyzed in detail. The results of this paper indicated that ignoring the 3D effect of the slurry trench will underestimate the stability of the slurry trench. The presence of suction in unsaturated soil is beneficial to the stability of the slurry trench, and the impact of suction is closely associated with seepage conditions and the characteristics of the soil. The increase in surcharge load can lead to a decrease in the FS, and its effect on slurry trench stability increases with the enhancement of the three-dimensional effect. The impact of different seepage conditions on the sliding surface of the channel wall of clay strata is more significant, while the effect on the trench wall of sand strata is negligible. [ABSTRACT FROM AUTHOR]

The use of prefabricated horizontal drains (PHDs) combined with vacuum preloading (VP) has emerged as a popular dredged slurry treatment strategy. However, few theoretical contributions are available to assess its consolidation characteristics in practical engineering design and applications. In this context, an analytical model is proposed to predict the consolidation behavior of the dredged slurry with assistance of PHDs subjected to VP. Initially, an equivalent cylindrical unit cell is established in accordance with the area equivalence principle. Then the governing equation and analytical solution are derived by converting the external loading into the lateral loading acting on the typical unit cell. In the current model, the layered filling process of dredged slurry and the corresponding layered layout patterns of PHDs are comprehensively incorporated. Furthermore, an in-depth assessment is conducted to explore the impacts of several crucial parameters on the consolidation performance. Additionally, a laboratory model experiment is carried out to treat the dredged slurry by a double-layer crosswise layout of PHDs in combination of VP. Thereafter, the accuracy and reasonability of the obtained solution are validated through degradation analysis and experimental data. Based on the parametric analysis and experimental outcomes, compared with prefabricated vertical drains (PVDs), the use of PHDs is observed to facilitate the transmission of vacuum pressure and ensure a more uniform settlement of dredged slurry, thereby ultimately improving dewatering efficiency. [ABSTRACT FROM AUTHOR]

Utilizing recycled concrete aggregate (RCA) is a countermeasure to address the scarcity of landfills and the depletion of natural aggregates. Surface modification techniques have been proposed and implemented to improve the properties of RCA; however, to our best knowledge, few investigations on improving RCA under various pozzolanic slurry concentrations and extended soaking durations have been done. This study comprehensively assessed the properties and microstructure of low-strength RCA treated with cement–fly ash slurry with different concentrations and soaking durations. The purposes of this study were not only to provide the optimal slurry concentration and treatment duration but also to explore the enhancement mechanism of RCA under various treatment conditions. The RCA from concrete with a low-strength grade of 20 MPa was soaked in cement–fly ash slurry at low and high concentrations (i.e., 30% and 70% by mass of RCA, respectively) for 24 and 72 h. The physical and mechanical properties of RCA before and after treatment were evaluated through water absorption and crushing value measurements, respectively. Additionally, the pore structure, Ca(OH)2 contents, surface morphology, and phase compositions of RCAs were evaluated through a mercury intrusion porosimetry test, thermal gravimetric differential thermal analysis (TG-DTA), scanning electron microscopy, and X-ray diffraction (XRD) analyses, respectively. The water absorption of treated RCA reduced by 9.2%–37.9%, whereas the crushing value decreased by 8.6%–26.9% compared with the untreated RCA. The TG-DTA results indicated a 22.3%–43.8% increase in the Ca(OH)2 content of treated RCA. The XRD analysis depicted a higher ettringite (AFt) peak in all treated RCA samples compared with the untreated sample. For both concentrations, with a 24 h treatment, the slurry infiltration effect was clearly observable, whereas the 72 h treatment resulted in the formation of a pozzolanic coating layer on the RCA surface. In conclusion, the optimal slurry concentration and soaking duration were 70% and 72 h, respectively. [ABSTRACT FROM AUTHOR]

This study aims to clarify the mechanism of slurry support and its effect at different stages of slurry infiltration in shield construction. The analysis of various expressions of slurry support throughout the entire excavation cycle is based on the theories of slurry infiltration effects and the cutting action of the cutters. Furthermore, the limit support pressure calculation method at the tunnel face is modified considering the slurry support mechanism observed during different slurry infiltration stages. Some of the main conclusions drawn are as follows. (1) When slurry deep infiltration occurs, the main form of slurry support is the seepage force acting on the soil skeleton. At this stage, the limit support pressure from the filter cake model will not be sufficient to meet the tunnel face stability requirements. (2) The effectiveness of slurry support is influenced by both the slurry infiltration state and the cutting action of the cutterhead. Slurry infiltration and shield tunneling together create a quasi-static equilibrium state, in which slurry support is effective only when the infiltration velocity corresponding to this state is greater than the critical velocity. (3) And the influence of shield tunneling parameters on the slurry support mechanism is significant. Compared with the cutter's penetration degree, the cutter's rotational speed has a more pronounced effect on the conversion rate of slurry support pressure at the shield tunnel face. [ABSTRACT FROM AUTHOR]

In recent years, the recycling and reutilization of shield tunneling residues (STR) have received extensive attention in underground engineering. To optimize the method of resource utilization of STR, this paper introduces a replacement method of STR slurry. The STR are incorporated into concrete and prepared as STR concrete (STRC) using a coarse and fine aggregate shell production process. By optimizing the mixing method of STR slurry, we obtained the best mixing process, and studied the influence of STR dosage and water–binder ratio (w/b) on the compressive strength of STRC. The results revealed that the air-dried STR preliminarily crushed to about 15 mm can be used to prepare STRC by extending the mixing time of STR slurry. The compressive strength of the concrete significantly depends on the dosage of STR slurry. The strength decreases significantly with the increase of STR dosage, and the recommended dosage is about 10%. The influence of the w/b on compressive strength is similar to that of ordinary concrete. A predictive model for the compressive strength of STRC was established by analyzing the relationship between the dosage of STR, w/b , age, and the strength of STRC. [ABSTRACT FROM AUTHOR]

Collapsibility significantly impacts the bearing capacity of pile foundations in loess areas. To improve the load-bearing capacity of piles, the pile-base postgrouting technique is widely used worldwide. However, there are still several related issues to be solved: the impact of loess collapsibility on the bearing capacity; the effectiveness of the pile-base postgrouting technique in enhancing the bearing capacity; and the diffusion pattern of the grout during the grouting process. To investigate these issues, this experiment utilizes a visual static pressure device combined with numerical simulation. According to the experiment, the maximum axial force and neutral point appeared to shift downward after grouting, resulting in a 17.5% increase in the bearing capacity of the pile foundation. Additionally, an increase in grouting pressure leads to a rise in both the number of shear cracks and the diffusion radius. As the permeability of the grout improves, the number of shear cracks and diffusion radii tend to stabilize after an initial increase. These discoveries enable a thorough analysis of the changes in side friction and base resistance of postgrouted piles in collapsible loess. Furthermore, they provide valuable references and guidance for the implementation of the pile-base postgrouting technique in loess areas. [ABSTRACT FROM AUTHOR]

This document is a closure to a previous paper titled "A Critical Assessment of the Effect of Initial Fabric on Key Small-Strain Design Parameters of Slurry-Deposited Silts and Sands." The authors respond to discussers' comments and clarify key aspects of the slurry deposition method. They argue that the rigorous slurry deposition (SD) method should be differentiated from other methods, such as dumped slurry (DS) or poured slurry (PS). The authors also address concerns about specimen uniformity, measurement of the critical state line, end restraint, triaxial specimen uniformity, and the representation of tailings deposits. They emphasize the need for further research and caution against relying solely on global void ratio concepts. [Extracted from the article]

This document is a discussion of a research paper titled "A Critical Assessment of the Effect of Initial Fabric on Key Small-Strain Design Parameters of Slurry-Deposited Silts and Sands." The authors of the discussion raise several queries and observations related to the proposed slurry deposition naming convention, measurement of the critical state line, end restraint, triaxial specimen uniformity, and the accessible in situ states and full-scale behavior of silts. They question the authors' claims and suggest alternative perspectives and evidence. The discussion provides valuable insights and raises important considerations for further research in the field of geotechnical engineering. [Extracted from the article]

Over the last 15 years, microbially induced calcite precipitation (MICP) has emerged as a possible solution to mitigate coastal erosion. To date, most MICP soil treatments that have been studied involve column injection using a pump. In recent years, MICP application through surface percolation has gained traction as an alternative technique, but data using this technique are limited. More recently, a new treatment recipe/technique was developed, and this technique was termed bioslurry. Like most MICP studies, research with bioslurry has concentrated on the column injection method, and surface percolation has received very limited attention. This paper discusses the treatment of Florida beach sand by surface percolating bioslurry. Researchers experimented with variations of the bioslurry recipe to optimize erosion resistance, which was assessed using a pocket erodometer combined with physical measurements. In addition, treated specimen morphology was preliminarily examined using X-ray diffraction and scanning electron microscopy. Results showed that erosion resistance was maximized when 15% to 25% of the specimens' pore volumes were filled with bioslurry and that this erosion resistance may be sufficient to withstand worst-case storm events after only one treatment. In addition, previous researchers always used a relatively long (i.e., ∼12 h) stir time when preparing bioslurry. Results presented here show that it may be possible to produce comparable data with much shorter stir times (i.e., 1 to 2 h). [ABSTRACT FROM AUTHOR]

The geotechnical tube technology has been widely used in the dewatering treatment of high-water-content slurries, such as engineering waste muds, mine water sludges, and dredging slurries. However, the existing engineering practice adopting the traditional geotextile tubes is characterized by low efficiency and difficult quality control. To address these issues, a new approach was developed by combining the geotextile tubes and vacuum preloading technology. In this method, several plastic drain boards were embedded in a geotextile tube as prefabricated horizontal drains (PHDs), and a vacuum was applied to promote drainage. The effectiveness of the proposed method was verified by a comparison test. A two-dimensional plane-strain analytical consolidation problem with a distributed drainage boundary was then formulated and solved to predict the consolidation process of soil in a vacuum preloaded geotextile tube. The analytical solution was validated against the results of a pilot field test, and then the influence of PHD spacing on the consolidation process was also discussed. Compared to the traditional geotextile tubes, the approach proposed in this paper promises good applicability and can effectively shorten the treatment time by 73.3% and reduce the water content of treated soils by 51.9%. [ABSTRACT FROM AUTHOR]

Colored asphalt mixtures have recently found extensive applications in roads and public spaces due to their contribution to traffic management as well as aesthetics and landscaping. The development of durable colored asphalts using various materials has been a hot research topic in recent years. Colored asphalt can be developed through the durable colored slurry seal mixture (CSSM) technology. The desired quality of CSSM requires particular attention to the mechanical performance and resistance against crack propagation due to temperature variations and traffic loads. This research aimed at investigating the effect of steel slag (SS) aggregate compared with natural aggregate (NA) on the fracture behavior and performance of CSSM in five different mixtures: NA100% (control sample), SS10%+NA90% , SS20%+NA80% , SS30%+NA70% , and SS40%+NA60%. The performance of CSSM was evaluated using an edge-notched disk bend (ENDB) specimen fracture test at three different temperatures (0°C, −10°C , and −20°C). Additionally, cohesion test, wet track abrasion test, loaded wheel test (LWT)-displacement and LWT-sand adhesion were carried out to further examine the samples. Comparison of the fracture behavior of colored mixtures revealed that the SS40%+NA60% mixture outperformed other mixtures. The results of other performance tests showed that the unique characteristics of SS40%+NA60% mixture improved CSSM performance against vertical displacements, bleeding, cohesion, and moisture sensitivity by approximately 40.2%, 4 7.3%, 28.6%, and 52.7%, respectively. This comprehensive assessment offers valuable insights into the effectiveness of SS as a proper alternative to NA in CSSMs. [ABSTRACT FROM AUTHOR]

To study the reinforcement mechanism of expansive slurry from a mesoscopic perspective, shear simulation tests were conducted on a slurry–fractured rock mass composite using PFC2D (version 5.00.35). The tests analyzed the distribution of cracks, the process of damage evolution, the distribution characteristics of intergranular contact forces, and the displacement of particles. The results indicate that (1) the volume expansion of the expansive slurry compressed the rock mass, causing the slurry particles to penetrate the pores of the rock particles. This process increased the contact area between the slurry and the rock mass, improved the friction, and intensified the degree of interlocking between the slurry and the rock mass, thus improving the bonding between them. (2) Both composite rock masses exhibited similar macroscopic damage patterns consistent with the laboratory tests. During shear tests, both composites experienced four stages of crack development: crack initiation, slow crack development, rapid crack development, and stable crack number. (3) The expansion stress, along with its reaction force and friction force, increased the integrity of the composite rock mass, reducing the differences in particle displacement direction and velocity. This led to improved internal deformation coordination within the composite rock mass, resulting in fewer cracks during shear tests. [ABSTRACT FROM AUTHOR]

The interfacial frictional resistance of anchor solids, bolt, and the surrounding soil of soil nails in the flexible support structures of frozen soil slopes is a key parameter for calculating and evaluating its stability. Based on a series of direct shear tests under the condition of a constant normal load boundary, the shear mechanical behavior of the interface between the soil and a cement slurry block under different soil temperatures, water contents, and normal pressures was studied, and the interfacial deformation mechanism was analyzed. The results show that in the thawing state, with the increase of water content, the shear surface moves from the side close to the soil to the side close to the cement slurry block. However, the shear plane is determined in the direct shear test, which makes the effect of the change of the soil's own strength on the interfacial shear strength smaller. In the frozen state, the behavior of the interfacial shear stress–shear displacement behavior at the same water content varies from strain-hardening type to strain-softening type with the temperature decreasing. The normal displacement is affected by temperature, normal pressure, and water content. At the same temperature, the maximum normal displacement gradually decreases with the increase of water content and normal pressure. At the same normal pressure and water content, the maximum normal displacement tends to increase and then decrease as the temperature drops. Still, the maximum normal displacement in the frozen state is more significant than in the thawing state. At the same water content and normal pressure, the interfacial peak shear strength shows a nonlinear increase with the decrease in temperature. At the same normal pressure and temperature, the interfacial peak shear strength delivers a linear increasing law with increasing water content. The peak interfacial cohesion increases with the decreasing temperature and increasing water content, and this phenomenon is more evident at lower temperatures. The interfacial friction angle does not change significantly with the rise in water content at the same temperature, but as temperature decreases, its average value increases significantly. The research results can provide a reference for the design of slope support structures in cold regions. [ABSTRACT FROM AUTHOR]

Slurry wall protection is the key to the success of the design and construction of underground diaphragm walls; however, in the analysis of its grooving mechanism, the original slurry in the surrounding environment was usually equivalated to the slurry pressure, while the slurry penetration characteristics and the formation of a filter cake were often neglected, leading to obvious defects in the existing literature. In this paper, by combining computational fluid dynamics (CFD) and the discrete element method (DEM), a model based on the strain softening constitutive equation was proposed to investigate the formation of a filter cake by the effects of slurry penetration and cementation and to calculate the stability of grooving. In this model, material parameters were used to describe the mechanical properties of the filter cake, and the microscopic parameters that were calibrated through experiments were used to explore the optimal particle radius ratio of the filter cake. Then, the feasibility and rationality of the model in describing the slurry penetration and failure trends were verified through comparative analysis. In the stability analysis, the safety factor was introduced to evaluate the impact of the slurry and other influencing factors on the grooving process. The results show that the properties of slurry and the environmental factors such as groundwater level have significant effects on the formation of the filter cake and stress distribution, thereby affecting the grooving effect. The findings of this study can provide useful guidance and reference for theoretical research and practical engineering. [ABSTRACT FROM AUTHOR]

The physicochemical combination method (PCCM), improving upon the conventional pure cement solidification method (PCSM), has been developed as an integrated and sustainable approach to treat and recycle slurry-like mud (MS). To facilitate the practical design of the PCCM, it is essential to establish the relationship between the strength of PCCM-treated MS and the governing factors. In this study, a comparison is made between PCCM-treated MS and PCSM-treated MS to clarify the differences in the microstructures and strength behaviors, and the influence of some key parameters (i.e., preloading pressure p, equivalent initial water content wei, and cementitious binder content wc) on the strength behavior of PCCM-treated MS is investigated via unconfined compression tests. The results indicate that flocculants play a crucial role in increasing the ductility of PCCM-treated MS, and the preloading process further enhances the toughness of PCCM-treated MS. Moreover, empirical equations of deformation modulus (E50) and failure strain (ɛf) are formulated based on the results of unconfined compression tests. Additionally, an attempt is made to predict the unconfined compressive strength (UCS) using a simple empirical equation based on the modified water/cement ratio. The main findings are of practical significance for the optimal design and application of PCCM in treatment of MS. [ABSTRACT FROM AUTHOR]

In the process of mining backfill transportation, inadequate pipeline layout or filling parameters can result in decreased stability in pipeline transportation. This instability can lead to blockages or pipe ruptures, often caused by the occurrence of partial filling during the transportation process. To address the issue of partially filled pipe flow during mining backfill transportation and effectively increase the full pipe height in the transportation process, theoretical analysis and numerical simulation methods were employed to study the causes and hazards of partially filled pipe flow in the transportation of tailings cemented backfill, as well as measures to enhance the full pipe height. By introducing the Bernoulli equation to analyze a simplified transportation model, a discrimination formula for identifying partially filled pipe flow during transportation was obtained. This formula summarizes the factors influencing the full pipe height and can be used to calculate the full pipe height in the transportation process of different filling mining areas. A numerical model was established based on this formula to simulate the occurrence of partially filled pipe flow. Combining the simulation results, the operational parameters of a lead-zinc mine in Yunnan, China, were designed and improved. This improvement significantly increased the full pipe flow height and reduced the failure rate in pipeline transportation. In the realm of mining pipeline transportation, occurrences of transport failures are not uncommon and are often attributed to the phenomenon of partially filled pipe flow. To tackle this challenge, we have devised a discriminative formula for partially filled pipe flow grounded in advanced engineering practices. Industry professionals can leverage our research findings to elevate fill heights in backfill transportation processes, employing strategies such as augmenting slurry concentration and streamlining pipe diameter. Beyond the confines of specific mining operations, this study stands as a universal reference for analogous transport systems. The efficacy of our approach has been validated through its practical application in a lead-zinc mine in Yunnan, China, yielding significant advantages. Through meticulous optimization of operational parameters, we have effectively elevated the fill height while concurrently mitigating pipeline transportation failure rates. This not only optimizes production efficiency but also substantially reduces maintenance costs, thereby providing robust support for mining operations. [ABSTRACT FROM AUTHOR]

This document discusses a research paper that explores the use of alternative binders to ordinary portland cement (OPC) in soil stabilization. The authors conducted a study using a binder composed of ground-granulated blast furnace slag (GGBS) and carbide sludge (CS) to stabilize clayey slurries. They found that the GGBS-CS binder performed better than OPC and proposed a pH-based approach to predict the optimum CS content. The document provides information on the unit weight of different materials, calculation of soil mass, and determination of GGBS and CS masses. It also presents data on the unconfined compressive strength (UCS) of different types of soil and suggests using a normalization procedure to fit the data to a single equation. The authors' experimental procedures are also questioned. [Extracted from the article]

Although trench failures observed in the field clearly show three-dimensional (3D) characteristics, the stability analyses of slurry-supported trenches are typically carried out under plane-strain assumptions. The factor of safety on trench stability produced by two-dimensional studies is also regarded as conservative as the favoring 3D end effects are not considered. To address this issue, a 3D rigid rotational mechanism formulated by a spatial discretization scheme is proposed for the stability analysis of slurry trenches in cohesive–frictional soils. The proposed method agrees well with the upper-bound solutions and corresponding optimal failure profiles of conventional rigid rotational mechanism (horn mechanism) of long trenches. Further improvement is achieved for short trenches as the discretization technique allows the mechanism to be generated with any given boundary conditions without assumption of standard geometry. Discussions on the influence of slurry parameters and soil strength parameters on trench stability are presented with results in the form of stability charts for convenience of application in practice. [ABSTRACT FROM AUTHOR]

A 193.5-m high concrete tube-shaped TV tower in the city of Nantong, China, was founded on short piled–raft footing, whose safety was threatened by implementation of four 10.9–26.5-m-deep excavations for an interchange subway station within close proximity. Considering the great damage potential of the TV tower associated with excavation-induced ground movement, a row of barrier piles consisting of bored piles was initially constructed between the excavations and TV tower. Field monitoring data indicated that the TV tower developed limited settlements during excavation of the two farthermost subway zones. However, it suffered notable settlements during excavation of the second farthest subway zone; hence, large-diameter metro-jet-system (MJS) piles along with bislurry piles were constructed between the excavations and TV tower to mitigate the adverse excavation influence. As a result, the tower gradually stabilized as construction continued, but it still exhibited an accelerated rate of differential settlement. Since excessive differential settlements might incur cracking, tilting, or even an overturning failure of the tower, it was determined finally to underpin the TV tower with long end-bearing steel pipe piles before excavation of the closest subway zone. With the aid of the comprehensive underpinning plan, the tower gradually became steady during excavation of the closest subway zone, without suffering structural damages or excessive deformations. The lessons and experience learned from this project as well as the extensive protection plans and measures are practically useful for engineers worldwide to safeguard high-rise superstructures sensitive to ground movement. [ABSTRACT FROM AUTHOR]

The rheological property of epoxy grout is related to whether the grouting material can completely fill the early cracks of the cast-in-situ concrete on the bridge deck. To reveal the rheological properties of epoxy grouting materials, epoxy grouting materials epoxy grouting material mixed with active diluent BGE (EP-I) and epoxy grouting material mixed with active diluent 1,4-BDE (EP-II) were prepared. The viscosity change of epoxy slurry with time under different diluent content was revealed. And the operational viscosity index was put forward to comprehensively evaluate the working characteristics of epoxy slurry with different diluents. Then, the gel time and groutability of two kinds of epoxy grout were compared and analyzed. Finally, the isothermal viscosity time-varying model of EP-I epoxy slurry was established. The results show that the viscosity of epoxy slurry decreases with the increase of diluent content, and the viscosity of epoxy slurry changes with time in the form of an exponential function. And the operational viscosity of EP-I epoxy slurry is significantly lower than that of EP-II, but its gel time was longer than that of EP-II. Both types of epoxy grout with 15% diluent can effectively fill the concrete early cracks (width 0.8 mm) within 10 min. Based on diffusion theory, single epoxy diluent butyl glycidyl ether (BGE) was more conducive to the penetration and diffusion of epoxy slurry. The isothermal viscosity time model of epoxy slurry can better reflect the relationship between viscosity and temperature, time. The goodness of fit between the model curve and the measured value is higher than 0.90, which has good reliability. [ABSTRACT FROM AUTHOR]

The vacuum preloading combined flocculation and solidification method (VP-FSCM) has been proposed in recent years to increase the efficiency of high-water-content slurries. The characteristic of the strength development of cement-treated mud, especially in the early stage, has significant effects on the consolidation process in the application of the VP-FSCM. An appropriate model for strength development can help decide the design scheme for the combining method to ensure that a high stabilization efficiency of high-water-content slurries is achieved. In this work, laboratory tests are conducted to investigate the strength development of mud with low cement dosage from a very early stage using vane shear tests and unconfined compression tests. After integrating the strengths obtained from the two approaches, the strength development behavior is analyzed, and the offset time is valued by performing a back-analysis using a modified Gallavresi's equation. It is found that a linear model can be built between the offset time and the water–cement ratio for a series of samples with the same soil type and binder type. Based on the model, the actual and predicted strength values fit well with a correlation coefficient of above 0.998. The model also agrees well with the test data from other literature, thereby testifying to its accuracy. By implementing the proposed model using consolidation theory, the consolidation proceeding time in the combined improvement method is determined. [ABSTRACT FROM AUTHOR]

Mud slurries are characterized by high water content and low strength; therefore, treatment (which included volume reduction and strength improvement in this study) was required before they could be transported, handled, and reused more easily. This study presented a method that combined prefabricated horizontal drains, vacuum preloading, and solidification (PHDVPS) for the rapid treatment of mud slurry with high water content. The performance of the PHDVPS method was experimentally investigated and compared with traditional methods that used only vacuum preloading or only solidification. Settlement and the mass of the discharged water (mvw) were monitored in model tests to investigate the dewatering efficiency (i.e., volume reduction). Then, unconfined compressive strength (UCS), permeability, X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) tests were conducted to investigate the mechanical, hydraulic, and microstructural properties of the PHDVPS-treated soils. The results indicated that the PHDVPS method significantly outperformed the traditional vacuum preloading and direct solidification methods for volume reduction and strength improvement. In addition, parametric studies indicated that the initial water content (wo) of mud slurry, cement content (Aw), duration of vacuum preloading (tp), and magnitude of vacuum pressure (σvp) had a significant influence on the performance of the PHDVPS method. [ABSTRACT FROM AUTHOR]

The use of prefabricated horizontal drains (PHDs) with combined surcharge and vacuum preloading is an effective improvement approach for dredged clayey slurries. However, there is no large-strain analysis method for PHD-induced consolidation of high-water-content sludge, even though it is a typical large-strain problem. This study develops a two-dimensional plane strain model based on Gibson's large-strain theory, considering horizontal and vertical flows, nonlinear hydraulic conductivity, and compressibility during the consolidation process. The alternative direction implicit (ADI) difference method is used to solve the governing equation. The proposed model is verified by the data from an analytical one-dimensional (1D) large-strain model and from field measurements. Compared with the improved small-strain models, the proposed model produces a slower consolidation of sludge. Furthermore, the analyses incorporating geometrical and mechanical nonlinearities show that, in comparison with the external load and the horizontal permeability, the spacing of the PHDs (horizontal and vertical) and the vertical permeability are more crucial factors significantly impacting consolidation efficiency. Specifically, smaller PHD spacing and greater vertical permeability lead to a more efficient consolidation. [ABSTRACT FROM AUTHOR]

Leachate, consisting of organic acids such as acetic acid (AA) and oxalic acid (OA), commonly is released into groundwater from municipal solid waste dumps and uncontrolled landfills. Slurry trench cutoff walls commonly are used to contain such contaminated groundwater, thereby protect the surrounding public and the environment. However, no studies have assessed comprehensively the effects of organic acid–laden groundwater exposure on the hydraulic conductivity and microscopic characteristics of sand–bentonite (SB) backfill in the cutoff walls. Several series of free swell, liquid limit, and flexible-wall hydraulic conductivity tests were conducted to quantify the effects of AA and OA exposure on the free swell index of bentonite and hydraulic conductivity and liquid limit of SB backfill. Results showed that the free swell index of bentonite and the liquid limit of SB backfill decreased with increasing concentrations of AA and OA. Exposure to AA yielded a lower free swell index of bentonite and liquid limit of SB backfill than those of OA with the same concentration. Increasing concentrations of AA and OA resulted in an increase in the hydraulic conductivity of SB backfills. Exposure to AA yielded higher hydraulic conductivity of SB backfill than OA with the same concentration. Mechanisms for increased hydraulic conductivity under organic acid exposure were ascertained based on the microstructure and compositional changes quantified by field-emission scanning electron microscopy (FESEM), mercury intrusion porosimetry (MIP), X-ray diffraction (XRD), X-ray fluorescence (XRF), cation exchange capacity (CEC), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR) analyses. [ABSTRACT FROM AUTHOR]

Whereas moist-tamped specimens of silts and sands are most used in engineering practice to characterize tailings, offshore sediments, and fluvial/alluvial deposits, design parameters derived from moist-tamping data sets can be significantly different from those obtained from slurry or underwater deposition. This study shows that moist-tamped silty and sandy specimens may exhibit phase transformation at stress ratios that are 25% to 50% lower than those observed for slurry-deposited specimens. Conversely, the small-strain stiffness of the moist-tamped specimens tested can be 50% higher than those from slurry deposition. With tailings dams' performance receiving increased worldwide attention due to recent dam failures in several parts of the world, this study provides new, specific, and concerning insights about the crucial impact that the selection of moist tamping can have on design parameters. More realistic and rigorous laboratory testing procedures involving tailings remain a key requirement for engineering assessments of tailings behavior. A novel slurry-deposition setup is presented that allows underwater reconstitution of silts, sands, and their mixtures, yielding high-quality uniform specimens. Systematic uniformity checks, which are mandatory to avoid segregation of silty materials, are described. A detailed analysis of typical errors affecting initial void ratio evaluation is also presented to ensure that comparisons between different methods are done with the highest degree of confidence possible. [ABSTRACT FROM AUTHOR]

The issue of water blocking by grouting in coastal areas has engendered the need for a novel numerical simulation method for grouting with a flowing water under tidal action, two-fluid tracking (TFT). This paper proposes such a method. First, based on the material derivative, the transport model of the residence time of injected slurry was derived. In addition, the residence time of injected slurry microgroups at any grouting time was obtained by solving the transport model. Further, the numerical characterization of slurry viscosity during grouting in flowing water was realized by introducing a time-varying viscosity function obtained from previous experiments. Then, based on the generalized tidal action model, the diffusion behavior and blocking mechanism of slurry under tidal effects were studied. The results show that: (1) under tidal action, the water velocity fluctuates and decreases, whereas the grouting pressure fluctuates and increases; (2) at the early stage of grouting, the diffusion pattern of slurry appears as a droplet, and the tailing phenomenon becomes more serious with an increase of tidal intensity; with the progress of grouting, the diffusion pattern gradually changes to U-shaped or elliptical; (3) the strong tidal action will reduce the retention rate of slurry, which is not conducive to the grouting blocking. The research results have been applied to the grouting treatment of a China Resources Cement (Hepu) limestone mine. This research can provide some useful guidance for grouting treatment engineering of water inflow in coastal areas. [ABSTRACT FROM AUTHOR]

The sleeve-valve pipe grouting technique is widely used in railway, highway, and house construction in China for its outstanding advantages in recent years. However, as the key parameter of sleeve-valve pipe grouting, the open-loop pressure of sleeve body material is still mainly determined by engineering experience. A sophisticated and reliable calculation theory and method have not been established. The role of sleeve body material used in sleeve-valve pipe grouting and the transformation of the acted object by the slurry pressure during the grouting process were systematically analyzed. The stress calculation method of the soil layer around the slurry outlet of the sleeve valve pipe in any inclined state and sleeve body material was obtained. Then, the open-loop failure condition of sleeve body material was proposed, and finally, the theoretical calculation method of open-loop pressure for sleeve-valve pipe grouting, considering the comprehensive influence of multiple factors, was established. Based on these calculation methods, the influence law of some factors of the open-loop pressure was studied deeply, and it was found that the open-loop pressure increases with the increase of the strength of sleeve body material, the elastic modulus ratio of sleeve body material to grouted soil, and the depth of grouting and decreases with the increase of the ratio concerning with Poisson's ratio of sleeve body material and grouted soil. The orientation (characterized by α and β) of the grouting hole in sleeve-valve pipe grouting has a noticeable effect on the open-loop pressure. When α is constant, the open-loop pressure increases obviously with the growth of β, and when β is constant, the open-loop pressure increases with the increase of α. Taking the DK107 + 105 frame jacking culvert project of the newly built Daye North–Yangxin railway as an example, the theoretical calculation method of open-loop pressure established in this paper was applied and verified. The calculated results showed that the outcomes calculated by using the method proposed in this paper are more consistent with the measured values of open-loop pressure at the engineering site and are better than the values of open-loop pressure calculated by these existing methods. The research results can support the development and improvement of sleeve-valve pipe grouting theory. [ABSTRACT FROM AUTHOR]

The combination of steel slag and cement to prepare green cement-based materials can help with environmental pollution issues, but the effectiveness of the products suffers versus cement without steel slag. This paper investigates the influence of cellulose fiber on the rheological properties, mechanical properties, and volume stability of steel slag cement cementitious materials. The results demonstrate that when cellulose fiber content increases, the slurry's rheological properties improve. When the cellulose fiber content was less than 0.5%, the strength of the samples at each age increased with the increased fiber content. At the same time, compared with the control blank group, the autoclave expansion rate of the samples was reduced by a maximum of 27.31%. When the fiber volume content exceeded 0.5%, the mechanical strength of the samples started to decline. The SEM results showed that the fibers inside the samples were entirely covered by hydration products after 28 days of hydration. The hydration products were primarily Ca(OH)2 crystals and C-S-H, which tightly bonded the fibers and the matrix, enhancing the performance of the samples. [ABSTRACT FROM AUTHOR]

Coal bottom ash was pulverized into a fine powder and dispersed within a polycarboxylate-water solution to reinforce the interfacial transition zone and matrix of recycled aggregate concrete. The dispersion was used as part of a three-stage mixing sequence that included direct coating over recycled aggregate prior to, and immediately after, the application of a cement clinker coat to enhance the aggregate–cement clinker interface and the bulk matrix properties. The results suggest that when adequately dispersed, the bottom ash slurry enhances the performance of the recycled aggregate concrete system. The addition of a well-dispersed bottom ash slurry coating reinforces both the interfacial transition zone and the bulk matrix. The slurry decreases porosity and unhydrated clinker content and increases the presence of high-density Calcium-Silicate-Hydrate (C-S-H) near the interfacial transition zone. This leads to significant increases in both tensile and compressive strength and fracture toughness (∼12%). [ABSTRACT FROM AUTHOR]

Extraction of recycled concrete aggregates (RCA) from construction and demolition waste is an effective way to induce sustainability in the highway sector. However, inclusions of these inferior materials could significantly deteriorate the performance of paving quality concrete (PQC) due to the presence of old adhered mortar (AM) around the RCA. Numerous techniques are available in the literature that primarily address the issues with AM for increasing the potential of RCA for concrete applications. However, the energy demand and associated emissions are higher in most of these techniques, whereas carbonation and slurry impregnation (SM) techniques are regarded as the best ways to economically enhance the characteristic of RCA for large-scale applications. The present study is the first of its kind to optimize the SM process for carbonated RCA for PQC roads; RCA was stockpiled in the natural environment in loose condition for around 12–14 months for fully carbonating the Portlandite phase. The parameters optimized are slurry material type (silica fume, fly ash, and cement), their concentrations (20%−60%), exposure duration (4–12 h), and RCA sizes (20 mm and 10 mm), whereas the porosity, toughness, absorption, and dry density were considered for process optimization. Finally, for process validation, various PQC performance parameters (fresh, mechanical, and durability) were determined. The findings suggest soaking the RCA sizes in any of the considered cementitious/waste material slurry at 40% concentration for 6 h for enhanced performance of both RCA and PQC made with treated RCA. [ABSTRACT FROM AUTHOR]

With the increasing height of new dams, the number of high-water-head and high-flow spillway buildings is gradually increasing, and concretes are required to have better abrasion resistance. Current standards offer a method for evaluating the abrasion resistance of concrete, but when evaluating the abrasion resistance of high-performance concretes, it is necessary to extend the test time to more than 120 h. In this study, an improved way of the current code-specified underwater method was proposed to shorten the testing time, called the high-speed underwater method (HSUM), and the test results of the two methods were evaluated using three-dimensional (3D) laser-scanning technology. It was found that the abrasion efficiency of the HSUM was about twice as much as that of the code-specified method. HSUM resulted in a significant acceleration of the concrete coarse aggregate abrasion process. The average abrasion depth of concrete was between 0 and 6.5 mm (HSUM after 15 h and code method after 30 h), and the abrasion mainly occurred on the surface of slurry, when the abrasion resistance of concrete was obviously affected by the strength and volume of slurry. When the average abrasion depth of concrete exceeded 6.5 mm, it entered the aggregate abrasion stage, and its abrasion resistance was influenced by the aggregate hardness and aggregate content, and the correlation with the slurry strength decreases. The surface roughness parameters Sq and Sa of HSUM concrete increase significantly compared with the code method. HSUM allows for a reduction in experimental time and high performance in evaluating the abrasion resistance of high-performance concretes or concretes with special aggregates (high-strength granite aggregates and cast stone aggregates). [ABSTRACT FROM AUTHOR]

In recent times, the employment of recycled aggregate concrete (RAC) for sustainable infrastructure development has enticed special interest from the research community owing to a greater emphasis on resource conservation and environmental protection. To apply such concrete in the modern-day construction industry, in-depth knowledge and thorough understanding of its fire resistance is imperative and an urgent need at the present time. Hence, this experimental study investigates the effect of elevated temperatures (25°C–800°C) on residual mechanical, physical, and microstructure performances of RAC strengthened via the coupling effect of chopped basalt fiber (BF) and pozzolana slurry treated recycled concrete aggregate (TRCA). To mimic real building fire conditions, concrete test specimens were heated to a specific target temperature in a controlled heating manner, and then their performance was assessed in terms of residual properties including compressive strength, splitting tensile strength, flexural strength, mass loss, physical appearance, and microstructure. Overall, the test findings revealed significant enhancement in residual properties of modified recycled concrete prepared by combined utilization of BF and TRCA. Moreover, in comparison with a reference sample, the BF-based recycled concrete demonstrated lower mass loss and surface degradation, especially beyond 400°C, that is attributed to the excellent thermal stability and reinforcing effect of BF. The microstructure observation evidenced improved matrix quality that contained better interfacial transition zones alongside added nucleation sites by BF. Lastly, based on the experimental data, simplified numerical relationships are established that will help predict the postfire performance of BF-reinforced sustainable concrete. [ABSTRACT FROM AUTHOR]

The use of carbide sludge (CS)-ground granulated blast furnace slag (GGBS) for clay slurry treatment has shown superior strength performance compared to ordinary Portland cement (OPC). To achieve a maximum level of unconfined compressive strength (UCS) of the CS-GGBS-treated slurry, there is an optimal level of CS, but this content varies with soil type and GGBS content. Optimal CS content is conventionally assessed by evaluating the UCS at 28 or 56 days. In this study, a rapid test method is proposed to estimate the optimum CS content in a few hours by measuring the pH, instead of UCS, of the CS-GGBS-treated slurry. Results show that the 28-day and 56-day UCS versus CS content curves of CS-GGBS-treated slurries are quite similar to their one-hour pH profiles. Hence, the pH versus CS content profile could be used to estimate the optimum CS content, i.e., the minimum CS content required to obtain a saturated Ca(OH)2 solution was estimated as the optimum CS content. The CS-GGBS-treated slurry with an estimated optimum CS content based on initial pH achieved a high strength level (≥91% of the maximum UCS) after curing for 28 and 56 days. Furthermore, the thermogravimetric analysis (TGA) results indicate that excess CS addition beyond the optimum CS content led to the generation of more hydrotalcite phases, but less calcium silicate hydrate (CSH), which contributed to the strength difference. [ABSTRACT FROM AUTHOR]

This paper presents an iterative horizontal method of slices (iterative HMS) for the global stability analysis of a slurry trench in layered cohesive-frictional soils. The iterative HMS differs from existing HMS models in terms of the assumptions on interslice forces. Preceding HMS techniques postulate that normal interslice forces can be evaluated from overburden pressures, which can lead to the violation of failure criteria along interslice boundaries. The iterative HMS ensures that a limit equilibrium system is established without violating the failure criterion throughout the entire soil mass. This is achieved by iteratively adjusting interslice forces by means of enforcing the failure criterion for the aforementioned problematic slice boundaries violating the failure conditions. The performance of the iterative HMS is evaluated in example problems of a slurry trench in uniform clayey soils and cohesive-frictional strata. The results are compared against solutions obtained using finite-element limit analysis (FELA) and a shear strength reduction FEM (SSRFEM). This comparative analysis shows that the adjustment in interslice forces is important for reasonably assessing trench stability conditions. A parametric analysis is performed by using the iterative HMS to show under what trench construction parameters the adjustment of interslice forces cannot be neglected in the stability analysis of a slurry trench. [ABSTRACT FROM AUTHOR]

In the prefabricated vertical drain (PVD) treatment of dredged slurry with high water content, fine slurry particles move toward the PVD membrane and accumulate around it due to the vacuum gradient. This process results in the formation of an almost impervious clogging column. The clogging column is cylindrical and symmetric about the vertical PVD axis, and it impedes vacuum consolidation of high water content slurry. A radial filtration model was created to describe the formation and growth of the clogging column using the equilibrium, continuity, kinematic, and constitutive equations in a cylindrical coordinate system. Essential components of the model are the moving boundary conditions for the clogging column–slurry interface and for the outer boundary surface of the slurry. The model accurately predicts temporal variation in the radius of the clogging column. Model predictions were compared to particle image velocimetry test results to validate the model. Real-time distributions of the void ratio, permeability, and effective stress for soil within the clogging column were also quantified and analyzed. The expansion of the clogging column was accompanied by compression of the soil skeleton. The distributions of the void ratio and permeability within the clogging column were highly nonlinear. The drainage rate of PVD was governed by the portion of the clogging column surrounding the PVD membrane. [ABSTRACT FROM AUTHOR]

A series of laboratory tests including flow consistency, viscosity, one-dimensional compression, and permeability were conducted on the fiber-reinforced cemented waste slurries obtained from a construction site to evaluate the fiber efficiency on the flow behaviors and compressibility-permeability properties. Results indicated that the fiber efficiency did not increase with increasing fiber length in this study because the waste slurry was composed of high montmorillonite and illite contents in this study. Fiber had a limited effect on the flow behaviors of the slurry mixture because the slurry reinforced by short fibers exhibited dispersive soil particles and fibers in the suspension. Longer fibers can bridge the soil particles and contribute to an aggregated fiber–soil matrix. A perfect fiber network with soil particles could be obtained at fiber content of 0.8%, where a well-fitted trendline can be obtained between slump flow and viscosity with high fiber efficiency. The cement content was found to dominate the compressibility of soil at higher water content. Fiber lengths in the range from 3 to 8 mm exhibited effective fiber reinforcement in terms of hydraulic conductivity. It is recommended to reinforce the waste slurry at fiber content of 0.8% with the optimal fiber length between 6 and 8 mm for the cemented waste slurry in this study. [ABSTRACT FROM AUTHOR]

Dredged clay slurry is usually regarded as a waste material due to its high water content, high compressibility, and low strength. Treating dredged clay slurry with carbide sludge (CS)–activated ground granulated blastfurnace slag (GGBS) can efficiently improve its strength. However, the compressibility and permeability behavior of CS-GGBS–treated slurry have not been investigated. In this study, a marine clay slurry with water content of 100% was treated with 60 kg/m3 of CS-GGBS, and the compressibility and permeability were evaluated. The untreated clay was also investigated as a reference. The results showed that although the treated slurries had a significantly higher initial void ratio (∼2.5) than that of the untreated clay (0.96), they yielded similar vertical strains, that is, around 25%–31%, in an oedometer test. The compression curve of the treated slurries consisted of two distinct phases, which can be elucidated by the evolution of the soil-cementation structure. At the pre-yield state, the cemented structure of CS-GGBS–treated slurry sustained the external stress, leading to insignificant strain. When the vertical stress exceeded the yield stress, the soil-cementation structure largely collapsed, and considerable strain occurred due to its high void ratio. In this stage, the compression index (Cc) of the treated slurry was three times higher than that of the untreated clay. Additionally, the treated slurry had a coefficient of consolidation (cv) 30–100 times greater than that of the untreated clay, which was attributed to its high permeability. During the oedometer test, the permeability of the treated slurry decreased sharply upon initial compression of the specimens, and then decreased at a lower rate as the void ratio decreased, presenting a bilinear correlation between permeability and the void ratio. [ABSTRACT FROM AUTHOR]

The infiltration of slurry in granular media plays an important role in face stability during slurry shield tunneling. This study investigates the effect of slurry viscosity in Fujian standard sand through a series of column tests combined with microstructural investigation, which remains unclear. The viscosity of slurry covers a wide range, from 1.8 to 2,248 mPa·s. Slurry particles in the low-viscosity test (1.8 mPa·s) fail to form an impermeable cake due to the loose stacking of slurry particles retained in sand voids, corresponding to a slight water pressure difference and relatively large permeability. For the high-viscosity test (2,248 mPa·s), an impermeable cake forms at a shallow depth; however, this internal cake is vulnerable to be disturbed and damaged due to its shallow thickness. Ultimately, one recommended viscosity, 56 mPa·s, is identified as a transition state with two-stage intact clogging, exhibiting an effective infiltration depth and intact internal cake that forms simultaneously. Experimental observations show a negative water pressure difference in the high-viscosity test, attributable to the siphonic principle. Furthermore, a measurement of slurry samples and solutes using the material observation apparatus could provide the microstructure evidence to interpret the effect of slurry viscosity in infiltration clogging. This study offers a reliable reference for interpreting the effect of viscosity on slurry clogging in infiltration performance. [ABSTRACT FROM AUTHOR]

This paper presents an improvement on a previous model for predicting the Marsh funnel (MF) test that is used in slurry shield tunneling for evaluating the rheological properties of bentonite slurries. The improvement focuses on the prediction of the dynamic part for fluids with small MF times. The velocity profile of the Herschel–Bulkley fluid in a laminar pipe flow condition is first investigated and a correction factor is introduced in the improved model. Comparisons of results from experiments and calculations with the previous model confirm the improved performance over the existing model. The rheological parameters obtained from the improved model show good resemblance to those obtained from a laboratory viscometer. The work also provides a reference to similar applications such as fluid transportation through pipelines where dynamic pressure dominates and therefore should be correctly predicted considering its velocity profile in a laminar condition. [ABSTRACT FROM AUTHOR]

Deep cement mixing (DCM) is an environmentally friendly technique for offshore ground improvement without dredging or much disturbance to the marine ecological system. Several field construction factors can influence the unconfined compressive strength (UCS) of cement-stabilized soil. In this study, key construction factors are evaluated referring to site investigation records, construction records, and quality test results of a large offshore DCM construction project. The key factors were attributed to geological conditions, construction procedures, and curing conditions. Specific field construction factors include fluctuations of tidal level, original soil type, volume fraction of injected water, volume fraction of injected cement slurry, injection rate of cement slurry, penetrating and mixing time per meter, curing age, and moisture content. The importance of these construction factors on the DCM strength has been quantified using a statistical method based on construction records. The injected water volume and original soil type are noted to be the two most dominant factors on the UCS of the treated soils. Longer mixing time improved the strength of the treated soils. [ABSTRACT FROM AUTHOR]

Graphene is expected to play a significant role as a capacitive deionization (CDI) electrode due to its exceptional characteristics. However, difficulties in achieving high specific surface area (SSA) reduces the sorption capacity and limits its usage in CDI. Effort taken toward improving the SSA of graphene by adding composites and through surface modification resulted in significant SSA with lower sorption capacity. Thus, the present study investigated the effect of the synthesis method and materials used to prepare electrode slurry (binder material) on SSA and specific capacitance. Graphene was synthesized employing Hummers, modified Hummers, and electrochemical exfoliation, and its quality was characterized based on X-ray diffraction, scanning electron microscope, and ultraviolet spectra analysis. The influence of binder type on specific capacitance was assessed by fabricating the electrode with commonly used two hydrophobic and two hydrophilic binders. Sorption analysis was also carried out to study the effect of SSA and specific capacitance of graphene with selected binders. The results revealed that electrochemically exfoliated graphene yield SSA of 1,529.8 m2/g with a sorption capacity 64% and 52% greater than graphene synthesized using the Hummers and modified Hummers methods, respectively. Usage of polyvinylidene fluoride (PVdF) binder resulted in a specific capacitance of 974.45 F/g and a sorption capacity of 32.73 mg/g. Thus, graphene's increased sorption capacity implies that the suitable method of synthesis and fabrication of electrodes with a suitable binder offers adequate SSA and specific capacitance by suppressing pseudocapacitance. [ABSTRACT FROM AUTHOR]

Concrete cutoff walls are becoming more widely used to control foundation seepage for earth–rock dams built on a thick soil foundation because of the urgent demand for hydroelectric energy. As the lifeline impermeable structure, the safety of the concrete cutoff wall is of great importance and deserves increased attention. However, such walls have often been analyzed through linear-elastic modeling and simulated as a continuous structure. The working behavior of the discontinued concrete cutoff wall with slurry cake is still unclear. This paper presents a three-dimensional (3D) nonlinear finite-element numerical analysis of the concrete cutoff wall in a thick soil earth–rock dam foundation considering the effect of slurry cake. The results indicate that the damage degree and range in the concrete cutoff wall are significantly affected by wall discontinuity and slurry cake thickness. Moreover, the panel joints may open at the downstream side of the wall under the action of lateral water pressure, which will reduce the effective thickness. The joint opening and tensile damage degree decrease with a reduction in panel width, while the compression damage at the lower part of the wall becomes more serious. The thickness of slurry cake should be controlled reasonably because of its obvious effect on damage behavior of the wall. The working behavior of the concrete cutoff wall can be improved by arranging the width distribution of the panel reasonably and dealing with the problem of the slurry cake. This study can provide useful basis and suggestions for the design of a concrete cutoff wall with slurry cake between panels in thick soil foundations. [ABSTRACT FROM AUTHOR]

Concrete piles are used conventionally to reinforce slurry trench against global collapse during excavation in surrounding soft soil layers. In this paper, the stabilizing forces acting on piles were analyzed with the framework of the upper-bound approach of limit analysis combined with a rotational failure mechanism in undrained soil conditions. A trench without pile reinforcement was considered first, and the results obtained in the proposed approach agreed well with those obtained through the limit-equilibrium and variational limit-equilibrium closed-form solutions. It was shown that the trench has a deeper critical excavation depth as the stabilizing force provided by piles becomes greater. In addition, the critical sliding surface tended to be shallower with a decrease in the ground surcharge coupled with a surcharge near the edge of the trench. Finally, the required stabilizing forces were needed to increase rapidly to enhance the safety factor of the trench to 1.0. However, due to the reinforcement of slurry pressure and soil self-stabilization, the stabilizing forces were not always required at all excavation depths; only when excavation exceeds a certain depth could the reinforcing effect of piles be exerted. [ABSTRACT FROM AUTHOR]

In laboratory testing, the liquefaction resistance of sands is typically evaluated using cyclic triaxial and simple shear tests. These tests cannot be used in a rigorous manner to systematically assess the effects of principal stress rotation and intermediate principal stress changes on the undrained cyclic response of sands. In this study, the effect of these two factors on the liquefaction resistance of Ottawa sand was investigated using a cyclic hollow cylinder apparatus. At similar initial states of fabric and mean effective stress following K0 consolidation, the liquefaction resistance of Ottawa sand deposited underwater can (1) decrease by 50%–80% as the major principal stress direction moves away from the vertical with σ2′=σ3′ , or (2) increase by 200% to 380% as σ2′ increases while σ1′ remains vertical depending on the liquefaction criterion (strain levels). When the stress state defined by the imposed boundary condition deviated from axisymmetric compression, the combined effect on the liquefaction resistance was governed by principal stress rotation. [ABSTRACT FROM AUTHOR]

To solve the problem of the unsatisfactory effect of grouting reinforcement in broken rock mass, a cement-based composite slurry was successfully prepared by using ordinary Portland cement as the main material in this study. By conducting a single factor test, orthogonal test, and organic compound modification test, the effects of different addition ratios of fly ash, clay and waterborne polyurethane, epoxy resin, and other organic materials on the grouting performance of cement slurry were analyzed. In addition, a grouting simulation test system was used to verify the reinforcement effect of the prepared composite slurry. The results indicate that the addition ratio of clay and fly ash has a strong influence on the strength and stone rate of cement slurry. The final setting time of the best mixed slurry can be shortened to 11 h, and the compressive strength after 28 days can reach 18 MPa. The composite slurry modified by organic materials has a reinforcement coefficient of up to 4.6 for crushed sandstone, which significantly improved the brittle failure phenomenon of the reinforcement stone body and, thus, has high application value. [ABSTRACT FROM AUTHOR]