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Copyright of Fly Ash Comprehensive Utilization is the property of Hebei Fly Ash Comprehensive Utilization Magazine Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Passive earth pressure behind retaining walls under rotational movements has been widely investigated recently. However, the behavior of surcharge loading under rotational movement has not been fully explored in the literature. This paper numerically investigates the impact of different types of wall movement; translation, rotation about the top and rotation about the bottom, on the two and three-dimensional passive earth pressure due to uniform surcharge loading. Results prove that the limit pressures under rotational mode are significantly lower than those in translational mode, ranging from 63% to 98% of those used in the literature. Overestimating coefficients in the design of retaining structures can lead to insecurity and instability. Furthermore, the distribution of passive earth pressure with depth is no longer rectangular. Shape factors are then evaluated to facilitate the practical application of passive earth pressure coefficients under rotational wall movements. [ABSTRACT FROM AUTHOR]

Negative skin friction (NSF) is an undesirable effect of piles observed in the dredged slurry of coastal reclamation areas. Herein, a testing framework was developed to investigate the pile NSF development pattern in the Wenzhou dredged slurry treated using the vacuum preloading drainage reinforcement (VPLDR) method. The vacuum pressure (VP) loss in field projects can cause variations in pressures in the treatment area and the VPLDR duration. A method to quickly quantify the treatment effectiveness of VPLDR is needed to ensure consistency. Two VPLDR cases with varying negative vacuum pressures (NVPs) and duration time were implemented to determine the main operating strategy for controlling the artificial consolidation effect. The pore water pressure (PWP) of soil was found to be associated with the undrained shear strength (Su) and was the primary indicator of the VPLDR effectiveness. The moisture content and water discharge only slightly influenced the Su magnitude. The equivalent reinforcement effect was achieved in the field VPLDR treatments by maintaining a constant PWP. Four tests on the model pile subjected to ground surcharge loading were conducted to study the NSF under various soil specimens and axial loading. NSF was observed in piles with surcharge loading and was reduced significantly in the reinforced slurry by the VPLDR. The surcharge-induced pile settlement can be decreased further with a small level of pile top load. The appropriate VPLDR and top load can weak the NSF caused by stacking. Therefore, these factors should be considered during pile construction in reclamation areas to restrain NSF. [ABSTRACT FROM AUTHOR]

In shield tunneling projects, the selection of an accurate model to calculate the mechanical response of segment structure plays a crucial role in the design and cost of the project. The shell–spring and beam–spring models are two widely used methods for this purpose. However, it is still not clear how accurate and different these models are in calculation results under surcharge load. Therefore, to accurately calculate the internal forces and deformation of the segment structure and clarify the difference between the two models' results, the shell–spring and beam–spring models were established based on a subway shield tunnel project in Zhengzhou city. The reliability of the models was verified by comparing and analyzing the differences in deformation results between the models and field measurements. Furthermore, the safety of the segment structure was evaluated according to the ultimate bearing capacity of the normal section. The results declare that: (1) In the shell–spring model, the internal force gradually reduces from the edges towards the center of the segment width, and the shield segment exhibits a prominent non-plane strain state. (2) The internal force of the beam–spring model is larger than that of the shell–spring model. The axial force difference between the two models is relatively small; meanwhile, there is a larger disparity in the bending moment. However, with an increase in surcharge loading, the discrepancy in internal forces between the two models gradually decreases. (3) The calculation results of the shell–spring model are close to the field-measured values and the shield tunnel model test values, which verifies the accuracy and reliability of the shell–spring model. Therefore, it is more reasonable to use the shell–spring model to calculate the mechanical response of the segment structure. (4) With an increase in surcharge loading, the safety of the shield tunnel decreases gradually. Therefore, surcharge loading above the shield tunnel should be reasonably controlled to meet the requirements of the normal use of the shield segment. This manuscript aims to provide a reference for the future design and optimization of the shield tunnels' lining structure. [ABSTRACT FROM AUTHOR]

Copyright of Fly Ash Comprehensive Utilization is the property of Hebei Fly Ash Comprehensive Utilization Magazine Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The surface surcharge leads to adjacent soil subsidence and further threat to the existing tunnels in underground space. In order to obtain the influence of surcharge loading on existing tunnel, the Boussinesq solution was used to obtain the vertical additional stress of the adjacent existing tunnel under surcharge loading, and the existing tunnel was simplified as an infinite Euler-Bernoulli beam lying on Vlasov foundation model. Considering the influence of the lateral soil of the existing tunnel, and then the deformation response of tunnel under surcharge loading can be obtained. Compared with the existing engineering data, the theoretical analysis is approach to monitoring data, and the reliability of the method can be verified. Compared with the degradation analysis of this method, the proposed method is closer to the engineering measured data. The last parameter studies show that the decrease of the longitudinal displacement and internal force of the tunnel with increasing the distance between the tunnel and surcharge. The longitudinal displacement and internal force of the tunnel can be increased with increasing surcharge loading. Increasing the tunnel stiffness not only reduces the longitudinal displacement but increases the internal force of the tunnel. [ABSTRACT FROM AUTHOR]

Batter pile is used to find a more effective way to stabilize the slope. Thus, these two questions "where is the optimal location of batter piles on earth slopes?" and "which inclination angle is most beneficial for pile in earth slopes?" arise. The numerical simulation was conducted to investigate the performance of slope reinforced by batter pile. The surcharge loading, inclination angle and pile location were varied while keeping geometry of the slope and the soil property constant. The surcharge loading was applied on the slope crest by steps. The inclination angle varied from 0° to 20°. The pile was placed at middle-down (MD), middle (MI), middle-upper (MU) and upper (UP) part of slope, respectively. A finite length of batter pile (10 m) was adopted, and the pile toe was free. Four series of numerical models were proceeded to search the optimum location and inclination angle for pile, one that provided maximum lateral resistance. By analyzing the slope deformation and pile bending moment, the effects of position and inclination angle of pile were determined. The following conclusions could be drawn: (1) The surcharge loading on the slope crest will influence the deformation of slope remarkably. Both the lateral displacement and settlement increases simultaneously with the raise of loading. (2) The lateral displacement and settlement of slope vary as the pile location moves from the crest to the toe. The slope of UP condition has the the minimum lateral displacement, following by MI, MD and MU condition. The ranking of settlement is same with the lateral displacement. That is to say, the UP condition is the best location for piled slope, followed by MI condition. (3) The batter pile is beneficial for slope engineering, which can not only reduce the deformation of slope, but also decrease the bending moment exerted on pile shaft. The inclination angle should be in a reasonable range, a relatively small inclination angle could not fully utilize the potential capacity of batter pile, while exaggerated inclination degree is not befitting for construction. The inclination angle of 15° is an optimal choice for batter pile in slope. (4) The inclination angle has mutual effect with the pile location, they should be considered synchronously. For comprehensive consideration, UP 10°, UP 15°, MI 15° and MI 20° are preferred options for the piled earth slope when subjected to surcharge loading. [ABSTRACT FROM AUTHOR]

Based on Barron’s equal strain consolidation theory, the consolidation governing equation of sand-drained ground under vacuum combined surcharge preloading is derived, and a general analytical solution is obtained, which considers the vacuum loading process, the time-dependent surcharge loading, the characteristics of the vacuum pressure decreasing along with the depth and radial direction, and the smear effect of vertical drains and the vertical flow. The correctness of the analytical solution proposed in this paper is verified by comparing the degenerate analytical solution with the existing analytical solution and the finite difference solution. Based on the analytical solution, the consolidation behaviors of sand-drained foundation are analyzed. The results show that the consolidation rate of sand-drained ground is accelerated with the increase of vacuum loading factor η. However, when η increases to a certain extent, the influence of the vacuum loading process on the consolidation rate of sand-drained ground can be ignored. The consolidation rate of sand-drained ground decreases with the increase of vacuum pressure attenuation coefficients k1 and k2. The consolidation rate of sand-drained ground decreases with the increase of vacuum pressure p0 and increases with the increase of final surcharge loading qu. With the increase of loading time Th1, the consolidation rate of sand-drained ground decreases gradually, and the consolidation rate is the largest under instantaneous surcharge loading.

Underground facilities are usually constructed under existing buildings, or buildings are constructed over existing underground structures. It is then imperative to account for the current overburden loads and future surface loadings in the design of tunnels. In addition, tunnels are often constructed beneath the groundwater level, such as cross-river tunnels. Therefore, it is also important to consider the water pressure impact on the tunnel lining behaviour. Tunnels excavated by a conventional tunnelling method are considered in this paper. The hyperstatic reaction method (HRM) is adopted in this study to investigate the effect of surcharge loading on a horseshoe-shaped tunnel behaviour excavated in saturated soft rocks. The results obtained from the HRM and numerical modelling are in good agreement. Parametric studies were then performed to show the effects of the water pressure, surcharge loading value and its width, and groundwater level on the behaviour of the horseshoe-shaped tunnel lining, in terms of internal forces and displacements. It displays that the bending moment, normal forces and radial displacements are more sensitive to the water pressure, surcharge loading and groundwater level.

This article examines the stability of retaining walls with relief shelves compared to the conventional cantilever wall using limit analysis integrating with the finite element method. The performance of such walls subjected to an incremental static uniformly distributed surcharge loading on the backfill surface is accessed in the terms of the magnitude of the surcharge carrying capacity of the walls before the incipient failure of the overall structure. From the analysis, it is noted that the provision of an appropriate number of relief shelves and their suitable locations and widths to the wall can bring significant improvement in the stability of the retaining wall compared to a wall without a relief shelf. Furthermore, it is noted that the width and location of the relief shelf are the major governing factors that are susceptible to modify the shape of the potential failure plane, the failure mode of the wall, and the backfill surface settlement profile. To maximize the stability of the wall subjected to static loading on the backfill surface, recommendations are laid for the optimum location and width of the relief shelves for a given height of the wall. [ABSTRACT FROM AUTHOR]

Engineers often face the challenge of constructing on soft soils that are associated with low bearing capacity and severe post-constructional settlements. In the subsurface zone, volume-change behavior of saturated soft soil is important in predicting the potential settlements. In this study, laboratory experiments have been conducted to monitor densification and consolidation processes of two soft geomaterials under incremental surcharge loading. During these experiments, densification of the geomaterials have been evaluated through a noninvasive scheme using electromagnetic (EM) methods. For this purpose, a time-domain reflectometry (TDR)-based approach has been accomplished by means of rod probe sensors. Changes of TDR waveforms under several surcharge loadings have been analyzed to establish soil properties, such as dielectric permittivity, volumetric water content, density, and porosity. Translating this laboratory-based nondestructive monitoring scheme to the field would potentially facilitate in management of ground improvement trials prior to, during, and after construction on soft soil deposits. [ABSTRACT FROM AUTHOR]

Culverts are often required under earth embankment to allow for the crossing of a watercourse, like streams, to prevent the road embankment from obstructing the natural waterway. The opening of the culvert is determined based on the waterway required to accommodate the design flood, whereas the thickness of the culvert section is designed based on the loads applied to the culvert. From the previous literature review, it is noted that the effect of haunch on the stresses of the culvert was not studied. Therefore, this research focuses on the impact of using haunches on the economy of the culvert design. This paper studies some design parameters of box culverts, such as the thickness of the haunch, the coefficient of earth pressure, the thickness of box culvert, and depth of fill on the top slab. The objectives show the effect of haunch on the stresses of the box culvert. The study investigated the variation in stresses and the cost comparison made for different width of the box culvert. The percentage reduction in the cost of culvert based on the presence of haunch is presented. At last, several significant conclusions are given based on numerical results as the presence of haunch is the best solution for decreasing the values of stresses from the economic point of view.

This study conducted parametric analyses to investigate the influence of structural loading (pile-head loading) on the development of negative skin friction in friction single piles and friction-end-bearing single piles in consolidating ground. Numerical effective stress-based mechanical-flow analysis models were built in ABAQUS software. The appropriateness of the modeling approach was verified by applying it to simulate a field model test described in the literature. For small surcharges, pile-head loading considerably reduces the depth of the neutral plane and therefore drag load for the friction pile. Under the same pile-head loads, the reduction in total drag load for the friction-end-bearing pile is smaller than that for the friction pile. However, when the friction-end-bearing pile is subjected to larger pile-head loads, the degree of total drag load reduction is comparable to that of the friction pile. Considerable pile-head displacement occurs under the combined action of pile-head and surcharge loadings. In contrast to the friction pile, the friction-end-bearing pile, because of the greater stiffness and strength of its bearing stratum, exhibits a significant reduction in negative skin friction, no bearing failure, and a smaller pile-head displacement when it is subjected to large pile-head loading. [ABSTRACT FROM AUTHOR]

Compared to the Rankine and Coulomb passive earth pressure theories, the logarithmic spiral theory considers curved failure surfaces, which is its greatest advantage. To improve the logarithmic spiral theory further, a new numerical method coupled with the Rankine and Coulomb theories was proposed and applied to determine the passive earth pressure coefficient of a sloping cohesive backfill under uniform surcharge loading. The method could yield either convex or concave failure surfaces, and the shape of the concave failure surface was assumed to be a logarithmic spiral. The Rankine and Coulomb theories were employed to determine the failure surface shape and distinguish convex and concave failure surfaces, respectively. Furthermore, approximate passive earth pressure coefficient equations for coefficients Kpγ, Kpq, and Kpc were proposed that consider the coupling effect of the soil weight, vertical surcharge loading, and cohesion. The predictions with the proposed method were compared to those reported by other authors. [ABSTRACT FROM AUTHOR]

The earth nailing system is a ground improvement technique used to stabilize earth slopes. The behavior of the earth nailing system is dependent on soil and nailing characteristics, such as the spacing between nails, the orientation, length, and method of installation of nails, soil properties, slope height and angle, and surcharge loading, among others. In the present study, a three-dimensional physical model was built to simulate a soil nailed slope with a model scale of 1:10 with various soil nail characteristics. The simulated models consist of Perspex strips as facing and steel bars as a reinforcing system to stabilize the soil slope. Sand beds in the model were formed, using a sand raining system. The performance of nailed soil slope models under three important nails characteristics, i.e., length, spacing and orientation, with varying surcharge loading were studied. It was observed that there is a reduction in the lateral movement of slope and footing settlements with an increase in length. It was found that the slope face horizontal pressure is non-linear with different nail characteristics. The increase in length and inclination of the soil nails decreased the vertical, horizontal stress and footing settlement, while the increase in spacing of the nails increased the vertical and horizontal stress behind the soil mass. [ABSTRACT FROM AUTHOR]

Water level drawdowns that occur outside and inside a fully, or partially, submerged slope will change the hydraulic gradient and enhance seepage forces, and may thus lead to slope instability and collapse. Existing research on this stability issue has primarily focused on the use of linear failure criteria and the associated flow rule. Little attention has been given to the effects of nonlinearity and the nonassociated plasticity of geomaterials, and of surcharge loading on slope stability. However, these conditions are more realistic for real-world cases. This study addresses this knowledge gap. The limiting surcharge on the top of submerged slopes subjected to water drawdown is analyzed in terms of nonlinearity and dilation effects using a limit analysis method. The optimal solutions were sought through optimization. The proposed method and its assumed failure mechanism were validated by comparing the results of the proposed method with results from finite element and finite element limit analysis. Parametric analysis and a case study are presented and indicate that as the water level difference increases, the bearing capacity of the slope decreases. In addition, it was found that the dilatancy effect has an effect on slope bearing capacity and that the inclusion of nonlinear effects enables better results. [ABSTRACT FROM AUTHOR]

This study numerically investigates the behaviour of a geosynthetic-reinforced soil (GRS) wall under surcharge loading. Data from a full-scale GRS physical model wall was used to verify the numerical analysis. The modelling was carried out using the two-dimensional finite difference computer program FLAC to verify the post-construction performance of a full-scale GRS segmental wall under surcharge loading. The real value of compaction induced stress (CIS) specified for the vibrating plate compactor used in the physical model wall was employed in the analyses. Two procedures for modelling the CIS found in the literature were used in the analyses: uniform vertical stress applied to the surface of each layer (type I) and uniform vertical stress applied at the top and bottom of each layer (type II). The results clearly showed that the numerical analyses using compaction procedure type II accurately represent the measured values obtained from the full-scale wall under surcharge loading as well as during construction. The numerical analyses considering type I compaction modelling overestimated the measurements during both construction and surcharge application. [ABSTRACT FROM AUTHOR]

The earth nailing system is a ground improvement technique used to stabilize earth slopes. The behavior of the earth nailing system is dependent on soil and nailing characteristics, such as the spacing between nails, the orientation, length, and method of installation of nails, soil properties, slope height and angle, and surcharge loading, among others. In the present study, a three-dimensional physical model was built to simulate a soil nailed slope with a model scale of 1:10 with various soil nail characteristics. The simulated models consist of Perspex strips as facing and steel bars as a reinforcing system to stabilize the soil slope. Sand beds in the model were formed, using a sand raining system. The performance of nailed soil slope models under three important nails characteristics, i.e., length, spacing and orientation, with varying surcharge loading were studied. It was observed that there is a reduction in the lateral movement of slope and footing settlements with an increase in length. It was found that the slope face horizontal pressure is non-linear with different nail characteristics. The increase in length and inclination of the soil nails decreased the vertical, horizontal stress and footing settlement, while the increase in spacing of the nails increased the vertical and horizontal stress behind the soil mass.

The safety factor of the slope subjected to wedge failure under surcharge load and uplift forces was obtained using an analytical model. A detailed parametric study conducted for the physical slope involved examining the impacts of the surcharge loads and uplift forces acting along the joint planes due to water pressure on the safety factor of the slope subjected to wedge sliding. The study results indicated that the safety factor of the slope susceptible to wedge sliding decreases with an increase in the surcharge loads and the uplift forces acting along the joint planes due to water pressure. The reduction in the safety factor due to an increase in the surcharge load is independent of the uplift forces acting along the joint planes. The rate of deterioration in the stability of the rock slope susceptible to wedge sliding depends on the rate of increase in the surcharge loads and uplift forces acting along the joint planes due to water pressure. The proposed expression can be useful for analytical stability analyses of the rock slopes subjected to wedge sliding induced by the surcharge load and uplift forces. [ABSTRACT FROM AUTHOR]

Culverts are often required under earth embankment to allow for the crossing of a watercourse, like streams, to prevent the road embankment from obstructing the natural waterway. The opening of the culvert is determined based on the waterway required to accommodate the design flood, whereas the thickness of the culvert section is designed based on the loads applied to the culvert. From the previous literature review, it is noted that the effect of haunch on the stresses of the culvert was not studied. Therefore, this research focuses on the impact of using haunches on the economy of the culvert design. This paper studies some design parameters of box culverts, such as the thickness of the haunch, the coefficient of earth pressure, the thickness of box culvert, and depth of fill on the top slab. The objectives show the effect of haunch on the stresses of the box culvert. The study investigated the variation in stresses and the cost comparison made for different width of the box culvert. The percentage reduction in the cost of culvert based on the presence of haunch is presented. At last, several significant conclusions are given based on numerical results as the presence of haunch is the best solution for decreasing the values of stresses from the economic point of view. [ABSTRACT FROM AUTHOR]

A series of field tests were conducted to examine the behavior of pile foundation subjected to adjacent surcharge loading in deep soft soils. The emphasis was on the pile deflection, bending moment, soil horizontal displacement and lateral earth pressure acting on the piles under different surcharge loading conditions. It was found that among the surcharge loading distance, intensity and width, the surcharge loading distance was the most significant factor affecting the adjacent piles in deep soft soils. The springback process of piles subjected to adjacent surcharge loading after unloading was a slow process changing with time. The mean lateral earth pressure on the pile facing the surcharge loading is slightly larger than that opposite to the surcharge loading. The pile bending moment and mean lateral earth pressure acting on the pile decrease with time due to the consolidation process of soft soil. 3D finite element model in ABAQUS is established to study the influence of consolidation process of soft soil on piles subject to adjacent surcharge loading. [ABSTRACT FROM AUTHOR]

Conventional drainage consolidation methods cause significant energy consumption and environmental issues. In this paper, a method combining siphon drainage and surcharge loading is proposed to drain water from soft soil with vertically installed prefabricated vertical drains (PVDs) and a siphon tube. To investigate the availability and effectiveness of this method, a laboratory physical modeling test was conducted to investigate the drainage and consolidation behavior. The laboratory modeling test results of this method were compared with the calculated results of the ideal sand-drained ground consolidation method to clarify the advantages and mechanism of this method. Comparison results show that the pore pressure and settlement in the proposed method developed faster than the calculation results of ideal sand-drained consolidation theory. About 10 m thickness of unsaturated zone can be formed by siphon drainage which produce a surcharge loading effect on the soil below the flow profile. Drainage is a very slow process in soft soil, and siphon drainage can work continually. Siphon drainage combined with surcharge loading is potentially a good alternative to drain water from soft clay economically and environmentally. [ABSTRACT FROM AUTHOR]

• Physical model tests for segmental tunnel linings under surcharge loading and excavation unloading. • A coupling effect index was proposed and the classification was presented. • The coupling amplification effect in complex conditions was analyzed. Surcharge loading and excavation unloading are two common engineering disturbances affecting the adjacent tunnel in congested urban areas. The coupling effect on segmental shield tunnel lining under loading and unloading conditions is still unclear. In this paper, physical model tests conducted in 1-g plane strain conditions were designed and performed to study the coupling effect of loading and unloading on shield tunnel. The results show that the response of segmental shield tunnel linings will be significantly amplified under the coupling conditions compared with the individual disturbance. A coupling effect index was proposed to evaluate the coupling degree of different disturbances. The classification was also presented, divided into favourable, zero, and unfavourable coupling effects. The tunnel response has a more significant coupling effect in the case of loading first and unloading later. There is a coupling amplification effect of 128% and 144% for the tunnel horizontal convergence and the springline near the excavation. [ABSTRACT FROM AUTHOR]

Soil lateral movement induced by surcharge load, e.g. banking in silos or embankment construction, leads to additional deformation and internal force on adjacent piles. Current Winkler foundation based methods (either stress loading method or displacement loading method) assume that the passive pile and the surrounding soil undergo the same horizontal displacement, which fails to account for the gap developed between the passive pile and surrounding soil, or the lateral flow of ground soil around the passive pile. This paper considers the relative movement between the passive pile and surrounding soil, proposes a simplified method with two independent lateral displacements of the passive pile and surrounding soil, and presents the assembling method of the stiffness matrix. With regard to Shanghai clayey ground condition, comparison and discussion are conducted on 8 models in total including soil springs with m method, p-δ method, Mindlin’s solution and Boussinesq’s solution through both stress loading and displacement loading. By comparison of the effect of spring stiffness values and loading type, a displacement loading method is recommended for engineering design, which is based on the soil reaction estimated with Boussinesq’s stress solution and the lateral stiffness back-analyzed with free field displacement. Finally, case studies are performed to demonstrate the design procedure of the proposed method, which proves this method’s feasibility and reliability. [ABSTRACT FROM AUTHOR]

Reinforced soil composites and mechanically stabilized earth (MSE) walls are frequently employed to carry large surcharge or footing loads. For the safety and serviceability of these reinforced soil structures, it is necessary to analyze the reinforcement load and compression of reinforced soil mass subjected to surcharge loading. In the research reported in this paper, an analytical method proposed by the writer was extended to meet these needs. The extended analytical method explicitly considers soil nonlinearity, soil dilatancy, soil-reinforcement interaction, and end restrictions of reinforced soil mass. Both plane-strain and triaxial stress states can be considered in the method. The applicability of the method for reinforcement load was validated against eight large-scale tests of reinforced soil mass or MSE walls, and the method for reinforced soil compression was validated against two large-scale tests. The compressions of four reinforced soil minipiers under surcharge loading were also predicted. The proposed method has the capacity to unify the analyses of reinforcement load and compression of a reinforced soil mass under low to medium surcharge loading. Some issues in the application of the proposed method are also discussed. [ABSTRACT FROM AUTHOR]

Retaining walls are an integral part of various infrastructural projects and are used to support deep excavations, or steep embankments, and deep basements. The earth pressure on these walls plays a crucial role in deciding the cross-sectional dimensions of the wall. An attempt was made in this research study to examine the variation of both the magnitude and distribution of earth pressure at-rest, and with reference to various possible wall movements, necessary to mobilize the active and passive earth pressures on the wall. Experimental studies were carried out on small-scale retaining walls supporting a cohesionless backfill material, and subjected to surcharge loading. Wall movement was modeled in the laboratory by allowing the wall to rotate about its base to simulate the case of rigid cantilever retaining walls. It was found that under surcharge loading, the earth pressure on the wall was gradually decreased as the wall moved away from the backfill but increased as the wall moved towards the backfill. It was also observed that the earth pressure due to surcharge load was greater near the top of the wall and decreased nonlinearly with depth down the wall. The lowest earth pressure occurred at the bottom of the wall, in contrast to the usual assumption that the earth pressure due to surcharge loading is uniform throughout the retaining wall. Finally, it was demonstrated that the distance between the surcharge load and the edge of the wall had a significant effect on the measured earth pressure values. [ABSTRACT FROM AUTHOR]

[Display omitted] • Soil failure surfaces are categorized as logarithmic spiral, linear and logarithmic. • Establish two methods to calculate the ultimate capacity of the soil-pipe system. • Propose a simple method to compute the pipe radial displacement using FBG strain measurements. Accurate and real-time estimation of underground pipelines' response to external loads is essential, in which the fiber Bragg grating (FBG) technique has shown great potential. A series of 1-g plane strain model tests were conducted to investigate the feasibility of using FBG sensors for monitoring the behavior of the soil-pipe system under surcharge loadings, while particle image velocimetry (PIV) was employed to measure the soil shear strain fields. The test results show three types of soil failure surfaces, i.e., logarithmic spiral, linear, and logarithmic. Regarding various failure modes, two theoretical methods to estimate the ultimate bearing capacity of the soil-pipe system are introduced. Detailed discussions are presented regarding the evolution of pipe strain measurement under different ground settlements. Finally, a method is proposed to calculate the radial displacements based on strain measurements for a shallowly buried pipe and a relative error below ±10% is obtained in this study. [ABSTRACT FROM AUTHOR]

• The coupling effect between DSS cable and surrounding soil is clarified. • The evolution process of the model slope under complex condition is recognized. • An empirical relationship is established to estimate the stability condition of such slope. In recent years, the construction of urban highway through slope excavation becomes more and more widespread. However, the surcharge loading induced by dense buildings is often neglected. For a better understanding of the deformation characteristics and associated failure mechanism of such slopes, a series of model tests have been carried out using distributed strain sensing (DSS) technology. The coupling between DSS cables and surrounding soil is the most critical factor affecting the validity of slope deformation measurements. Therefore, a cable pull-out test is conducted to investigate the coupling effect. It is founded that 200 KPa is the critical confining pressure (CP). Once the CP exceeds this value, the synchronous deformation of DSS cable and soil can be guaranteed, which can be regarded as criterion to guide laboratory test and in-situ monitoring. After the deformation compatibility is ensured, a surcharge loading model test is designed and DSS cables are horizontally and vertically installed. The strain variation exhibited on the DSS cables reveal that the crest and toe areas of the slope show a thrust load-induced and retrogressive failure patterns respectively. It indicates that a shadow sliding surface can occur during slope excavation, which is rarely witnessed in previous studies. The safety factor can be calculated by the slice method. It is founded that the horizontal maximum strain can reflect the stability of the model slope and an exponential function has been established. The results are likely to provide a good indication of the stability of such slopes. [ABSTRACT FROM AUTHOR]

Current analytical solutions on the ground movements and stresses induced by shield tunneling in soft soils are generally based on the instantaneous excavation behavior. Furthermore, previous studies seldom took account of the influence of surcharge loading during tunnel excavation process. This paper introduces a complex variable analytical solution to estimate the deformation and stress of surrounding soils caused by shield tunneling subjected to surcharge loading considering the soil rheological mechanisms. The non-uniform convergence deformation boundary is adopted at the tunnel opening and the Boltzmann viscoelastic model is employed in the time-domain solution so as to consider the displacement controlled boundary and the rheological effects. The accuracy of complex variable time-dependent solution is then verified by comparisons with in-situ observed data, and good consistency is obtained. Finally, the parametric analyses are performed to evaluate the influence of correlative coefficients in Boltzmann viscoelastic model and paramount factors of surcharge loading on the feedback around tunneling. The ratios of the peak values of final surface settlements induced by tunneling in viscoelastic soils to those in elastic soils in the initial period vary approximately from 40% to 120%. The soil stresses around the tunnel increase about 50% significantly over time. [ABSTRACT FROM AUTHOR]

• Large-scale model test is applicable to the study of the tunnel stability. • DIC system can record the complete failure process of tunnel. • The FDM-DEM method offers further insights into progressive failure of tunnel. • The progressive failure process of tunnel is controlled by stress loosening zone. • The results can give insights into excavation safety and support design of tunnel. The tunnel instability accidents caused by surcharge loading could even lead to ground settlement or collapse, damage to the existing municipal pipelines or inclination of the surgical buildings. Series of large-scale physical model test was conducted in this paper to reveal the failure mechanism of tunnel in soft rock subjected to surcharge loading. The non-contact full-field displacement measurement (i.e. Digital Image Correlation, DIC) was employed to obtain a detailed deformation of surrounding rock after excavation. A coupled numerical method combing the continuum (Finite Difference Method, FDM) and dis-continuum (Discrete Element Method, DEM) analysis was used to deal with the failure mechanism of tunnel excavation in rock mass. Good agreements between physical model test and numerical analysis approve the accuracy of the proposed FDM-DEM numerical model. It is found that the collapse mainly occurred in tunnel roof rather than in tunnel sidewall. The collapse zone shows a step-type increase with the increase of surcharge loads. The stress loosening zone (SLZ) in tunnel roof is larger than that in tunnel sidewall. The thickness of SLZ in tunnel roof can be used to design the length of the formed pressure anchors. The proposed large-scale model test with DIC method is applicable to the tunnel engineering study. Moreover, the results in this paper give some insights to secure excavation works and optimize supporting structures. [ABSTRACT FROM AUTHOR]