Search

This study aimed to use numerical modeling to investigate the behavior of soil slopes under various inclination angles of soil nails and surcharge load conditions. Numerical modeling and analysis are performed using finite element software PLAXIS 2D. In this study, the stability of a soil slope is investigated at different soil nail inclination angles, viz., 0°, 5°, 10°, 15°, 20°, 25°, and 30°. A surcharge load of 80 kN/m is applied at distances of 2 m, 4 m, and 6 m from the slope edge. The results show that the safety factor increases with increasing soil nail angle under a constant surcharge load. Similar results were obtained when the distance of the surcharge load increased from the slope edge. In addition, the bending moment and shear forces in the soil nails decreased with increasing inclination of the soil nails and increasing distance of the surcharge load from the slope edge. The slope with nails at 20° is the most stable slope, with safety factors of 1.647, 1.610, and 1.692 for the three surcharge loads. Similarly, minimum shear forces of 2.298, 2.684, and 1.183 kN/m and bending moments of 0.4132, 0.4075, and 0.1236 kN-m/m are predicted when the nails are inclined at 20° for the above three cases of surcharge loading, respectively. [ABSTRACT FROM AUTHOR]

Natural disasters such as landslides are frequent occurrences around the world. Despite the many studies conducted on slope behavior, the loss of countless lives and valuable property continues. This study employed the Limit Equilibrium Method (LEM), simulated using SLOPE/W software, based on the Mohr-Coulomb failure criterion to examine the behavior of a silica sand slope under surcharge load. The properties of silica sand, such as dry unit weight (γd), saturated unit weight (γsat), angle of internal friction (φ), and soil cohesion (c), were determined through compaction and consolidated-drained (CD) triaxial tests. The computed Factor of Safety (FOS) value from the SLOPE/W analysis is 0.955 at an applied surcharge load of 6.4 kPa. The result was then compared with Finite Element Method (FEM), simulated using Plaxis 3D software based on Strength Reduction Method under the same loading conditions. The results from both analyses showed that the Plaxis 3D analysis generally gave a higher FOS value (6.321) compared to the FOS value obtained from the SLOPE/W analysis (0.955). The shape and critical slip surface are almost identical for each analysis. The results of both numerical simulations were then compared to the experimental testing. The LEM method provides a more realistic indication of FOS. A clear understanding of the approach employed in the LEM and FEM analyses determines the validity of the analysis carried out. [ABSTRACT FROM AUTHOR]

Culverts are essential under earth embankments to allow watercourses, such as streams and nallas, to pass through without obstructing the natural flow. They help manage floodwaters on both sides of the embankment, reducing water levels and mitigating flood risks. Culverts come in various shapes, including arch, slab, and box configurations, and can be constructed from materials such as masonry or reinforced concrete. Culverts, embedded within earth embankments, are subjected to traffic loads similar to those on the road and must be designed to accommodate these loads. This paper focuses on the structural design and parametric analysis of RCC box culverts, both with and without cushion. Design parameters such as size, invert level, and layout are determined based on hydraulic considerations and site conditions, with the cushion depending on the road profile at the culvert location. The study examines various load cases (e.g., empty box, full box, surcharge loads) and factors such as effective width, braking force, load dispersion through fill, impact factor, and earth pressure coefficient as per IRC codes. It provides a comprehensive discussion on code provisions, design considerations, and justifications for the structural design of RCC box culverts, ensuring they can withstand maximum bending moments and shear forces. [ABSTRACT FROM AUTHOR]

Time-dependent characteristics (TDCs) have been neglected in most previous studies investigating the deviation mechanisms of bridge pile foundations and evaluating the effectiveness of preventive measures. In this study, the stress-strain-time characteristics of soft soils were illustrated by consolidation-creep tests based on a typical engineering case. An extended Koppejan model was developed and then embedded in a finite element (FE) model via a user-material subroutine (UMAT). Based on the validated FE model, the time-dependent deformation mechanism of the pile foundation was revealed, and the preventive effect of applying micropiles and stress-release holes to control the deviation was investigated. The results show that the calculated maximum lateral displacement of the cap differs from the measured one by 6.5%, indicating that the derived extended Koppejan model reproduced the deviation process of the bridge cap-pile foundation with time. The additional load acting on the pile side caused by soil lateral deformation was mainly concentrated within the soft soil layer and increased with the increase in load duration. Compared with t = 3 d (where t is surcharge time), the maximum lateral additional pressure acting on Pile 2# increased by approximately 47.0% at t = 224 d. For bridge pile foundation deviation in deep soft soils, stress-release holes can provide better prevention compared to micropiles and are therefore recommended. [ABSTRACT FROM AUTHOR]

• An analytical approximant solution is presented for a shallow tunnel loaded by surcharge load and gravity in slope ground. • The presented method overcomes the mathematical difficulty of finding mapping function using only complex variable theory. • The derived solution is straightforward and featured as high accuracy of calculation results. • The influence of surcharge loads position, tunnel location and slope topography on ground response is revealed. For shallow buried tunnels under slope, overloading on the ground surface and unloading of excavation both significantly influence the stability of the tunnel surrounding rock and slope. This study proposes an analytical approximate solution for the stress and displacement around shallow buried circular tunnel under slope boundary. In derivation process, the original problem is divided into two models: Model A is a slope plane without any holes subjected to gravity and surcharge load along the ground surface, and Model B is a tunnel contained in a slope plane loaded by released stresses along the tunnel boundary. Furthermore, Model B is decomposed into another two models: Model B 1 represents a slope without holes subjected to virtual surface force along the ground surface, and Model B 2 is an infinite domain containing a tunnel loaded by another virtual surface force along its boundary. Two sets of virtual surface forces are then achieved by an iterative calculation. The solution, which strictly meets all stress boundary and compatibility conditions of the original problem, are ultimately solved by superposing the solution of Models A, B 1 and B 2 , respectively obtained by the method proposed by the authors (Models A, B 1) and complex variable theory (Model B 2). The convergence of iteration process and good agreement between the derived and numerical results under the same assumptions verify the correctness of the proposed solution. Furthermore, a parametric investigation is performed to investigate the influence of surcharge load position, slope topography and tunnel position on the stress and displacement around the tunnel and near the ground. The proposed solution is of great value for the conceptual understanding of mechanical behavior of shallow tunneling in slope terrain and for verifying the numerical models. Moreover, the solution is useful for the preliminary design of tunnels at shallow depth under slope topography. [ABSTRACT FROM AUTHOR]

This paper reports a typical case history of deep braced excavation for constructing the main bridge cushion cap of the Yangwan River Bridge to explore the excavation performance under embankment surcharge load. Three-dimensional finite difference analysis, simulating the whole construction process of this case history, was performed to capture the effects of the embankment–excavation distance, revel level, and excavation bottom sealing on the responses of the earth retaining structure and the ground. It was found that both the ground surface settlement and the retaining structure deformation are larger on the near-embankment side than the far-embankment side. The responses on the near-embankment side are more sensitive to the embankment–excavation distance and the river level. However, the effects of these parameters diminish greatly when the embankment–excavation distance exceeds 1.5 times the excavation depth. The excavation bottom sealing measures can reduce the retaining structure deformation, and effectively restrain basal heave. This restraint weakens as the excavation bottom sealing thickness exceeds 1 m. [ABSTRACT FROM AUTHOR]

ABSTRACTThis paper examines the impact on Factor of Safety (FS) value due to the variation in distributed load (LD), Crest length (CL), shear strength (τ), and shear stress (σ) both in seismic and non-seismic conditions. The main purpose of this paper is to develop correlations between these parameters, which can be used in any slope stability analysis design project. Forty number of analyses are performed by considering different soil material properties. Slope stability analysis is performed using Slide software and correlations are developed using Statistical Package for Social Sciences (SPSS) software as well as with the help of Microsoft Excel. The analysis results indicate that the seismic slope stability analysis gives optimum value for slope FS and therefore it is highly recommended to perform and give preference to seismic slope stability analysis of any soil slope to compute and recommend FS value. The main novelty of this paper are the eight new correlations. These correlations can be used in slope stability projects like earthfill dams design, embankments, or any slope design project or case study to know about the slope factor of safety in detail.

In this paper, a simplified prediction formula of ground settlement induced by deep foundation pit excavation is proposed, especially suitable for ground overloading near a foundation pit, such as embankment surcharge load, which is carefully considered via the means of load equivalence. The ground settlement induced by foundation pit excavation and embankment surcharge load is determined by the modified skewness prediction formula and the simplified Boussinesq solution, respectively, and it is assumed that no coupling effect exists between the two settlement sources. In addition, this paper improves the determination of the maximum settlement location by combining calculus and curve fitting, replacing the existing prediction formula which relies heavily on engineering experience to determine the maximum settlement point. The predicted value obtained using this method comes close to the measured value, and the deviation of the maximum surface settlement value is controlled within about 5% in the three cases introduced, of which the accuracy is higher than the existing prediction formula. [ABSTRACT FROM AUTHOR]

This study applied the three-dimensional finite different method (FDM) to model a single pile subjected to passive loading due to a new embankment in extensively soft soil. Four important parameters (pile bending stiffness, distance between the long edge of the loading area and the pile (D), embankment height, and cushion thickness) were investigated to evaluate their effects on the deformations and stresses on the passive pile. The displacement of the pile shaft, vertical displacement of the foundation soil, excess pore water pressure (EPWP), and lateral earth pressure were analyzed. The numerical results showed that the lateral displacement of the pile was significantly affected by the four parameters. The maximum lateral displacement decreased dramatically for the high-stiffness pile. A cushion thickness of

Deep foundation pits are usually located in densely built-up areas, and its stability is affected by adjacent structures. A few studies have considered the effect of surcharge load on the stability of foundation pits; such effect may lead to excessive deformation or even collapse. To determine the mechanical response of dual-row pile walls (DRPWs) in foundation pits under the action of surcharge loading, a physical scaling model test and numerical simulation were conducted, and a method to determine the influence of overloading was provided. Five physical scaling model test schemes were proposed; electronic displacement gauges, strain gauges, and pressure sensors were installed to test the static response of a DRPW under excavation and surcharge load. The effects of loading distance and load magnitude on the bending moment, pile head displacement, and pile shaft deformation of DRPWs were also investigated. The relationship between overload and the mechanical response of DRPWs was quantified, and the results of physical model tests were verified by numerical simulation. Results showed that surcharge loading has a negative effect on the stability of DRPWs in foundation pits, and the deformation of DRPWs is negatively correlated with the loading distance of surcharge load. The critical value of the loading distance of surcharge load is 0.5 times the excavation depth. When the loading distance is less than the critical value, the overload causes remarkable displacement and inner force of the DRPW. Moreover, the deformation of the DRPW is positively correlated with the surcharge loading magnitude. With the increase in vertical loading, the displacement of soil increases nonlinearly, and the circular sliding surface through the excavation bottom is finally formed. The results of this study provide some references for the design and construction of DRPWs. [ABSTRACT FROM AUTHOR]

• Viscoelastic solutions of ground responses induced by non-circular tunnel excavation in semi-infinite ground are provided. • Surcharge loads, gravity induced initial stresses and the internal forces due to liner installation are considered. • A parametric study is performed for shallow noncircular tunnels. The construction of noncircular tunnels at shallow depths has become increasingly common in urban areas to efficiently utilize underground space. In general, noncircular tunnels may cause high stress concentrations and large settlements. In addition, the stability of shallow tunnels affected by the structural loads/surcharge loads on the surface is too significant to ignore. This study presents new analytical solutions to efficiently predict the stresses and displacements around shallow noncircular tunnels in rheological rock. The key factors, i.e., any viscoelastic characteristics of the surrounding rock, arbitrarily distributed loads exerted on the ground surface, arbitrary tunnel shapes and pressures exerted at the internal tunnel boundaries due to liners or water pressures, are fully taken into account. A noncircular tunnel in the half-plane was mapped into an anulus by employing the conformal mapping function. Then, the elastic solutions of the problem are obtained by complex variable theory combined with the mapping function. Based on the elastic solutions and the extended corresponding principle for the viscoelastic problem, time-dependent analytical solutions are obtained for the ground assuming any viscoelastic models. The analytical solutions are verified by the good agreement between the analytical and FEM results under the same assumptions. Then, a parametric study is finally performed to investigate the influence of the location or range of the surcharge, tunnel burial depth and lateral pressure coefficient on the ground stresses and displacements. The proposed analytical solution can provide insight into the mechanical behavior of shallow noncircular tunnels under surcharge loads, as well as an alternative method in the preliminary designs of future shallow tunnels. [ABSTRACT FROM AUTHOR]

Most of the damaging geo-hazards recorded in modern history are caused by soil swelling or expansion. Therefore, proper evaluation of a soil's capacity to swell is very crucial for the achievement of a secure and safe ground for civil infrastructures and related land developments which are founded on the soil. In order to simulate as well as estimate the heave that can occur under field conditions, laboratory one-dimensional oedometer vertical swell-strain testing are most frequently used. Hence, in this brief, one-dimensional swelling tests adopted to measure soil swelling on laboratory-engineered and natural soils covering various regions on the globe are reported. The testing standards and procedures followed in the measurement of one-dimensional swelling are those enumerated in the American Standards for Testing of Materials (ASTM), and American Association of State Highways Transport Officials (AASHTO). Slight modifications to the measurement procedures (such as the use of different surcharge loading and custom-made consolidation rings) reflecting special laboratory testing conditions and for the purposes of comparisons, are also reported.Corresponding soil properties characterising the dataset includes moisture content, void ratio, specific gravity, unit weight, liquid limit, plastic limit, plasticity index, clay content, silt content, maximum dry unit weight, optimum moisture content, and soil activity index, all of which are known to bear either direct or indirect influences on soil. Determination of the state of compaction of the soils where applicable, are carried out based on the American Standards for Testing of Materials (ASTM), Turkish Standards (TS), American Association of State Highways Transport Officials (AASHTO)and a combination of both standard and modified efforts. A total of 395 data samples on soil swelling potential are reported. With regards to the corresponding soil properties, a total of 219 data records of soil specific gravity, 321 data records of initial moisture content, 163 data records of void ratio, 273 data records of dry unit weight, 347 data records of liquid limit, 347 data records of plastic limit, 395 data records of plasticity index, 209 data records of activity index, 339 data records of clay content, 174 data records of silt content, 246 data records of optimum moisture content, 228 data records of maximum dry density and 347 data records of Unified Soil Classification System (USCS) are presented. Finally, the dataset of one-dimensional soil swelling described herein are intended to aid geotechnical engineers and researchers who are involved in statistical correlation studies, data analytics, and machine learning predictions using soft computing methods mostly aimed at evaluating soil expansion especially during the preliminary phases of soil investigation and foundation design.

This paper presents a case study on the improvement of thick marine deposits. A new method that combines vacuum pressure and surcharge load with no need for a sand cushion is proposed and evaluated. The main features of this method are as follows: (1) each integrated prefabricated vertical drain (PVD) is connected directly to a branch pipe, which is in turn connected to a main pipe with a T-shaped connector, and (2) a less expensive hill-skill soil layer is used to replace the sand cushion. After improving the soil by using this method, the total ground settlement, the lateral deformation and the undrained shear strength were all greater for a 20-m PVD than for a 15-m PVD. The average degrees of consolidation achieved were both greater than 80%. This method could provide design criteria for reclaimed land in other projects. [ABSTRACT FROM AUTHOR]

Using the classical (linear) Mohr–Coulomb (M–C) failure criterion, the failure mechanism of slopes is commonly treated as a completely shear failure. However, the tension failure mechanism has also been commonly observed in landslides, especially for those covered by cemented soils geometrical. Considering only the shear failure would overestimate the tensile capacity of geomaterial, which can lead to an optimistic result. In this paper, a modified M–C failure criterion with zero or low tensile strength (tension cutoff) was introduced that can characterize the shear–tension failure feature of slopes well. Combined with the limit upper bound theory, the expressions of stability factor (Ns) for slopes were derived considering (1) only soil self-weight; and two external conditions, (2) surcharge load, and (3) seismic load. Further, a detailed parametric analysis was conducted. The results show that the slope stability was greatly influenced by the surcharge coefficient (qt) and the horizontal seismic acceleration coefficient (kh). The influence of the degree of tension cutoff (ζ) on the slope stability strongly depends on the values of slope angle (β) and internal friction angle (φ). The difference in Ns under two extreme cases (ζ = 0 and ζ = 1) was significant, and the difference was more pronounced with the introduction of surcharge and seismic load. [ABSTRACT FROM AUTHOR]

In this paper, a simplified prediction formula of ground settlement induced by deep foundation pit excavation is proposed, especially suitable for ground overloading near a foundation pit, such as embankment surcharge load, which is carefully considered via the means of load equivalence. The ground settlement induced by foundation pit excavation and embankment surcharge load is determined by the modified skewness prediction formula and the simplified Boussinesq solution, respectively, and it is assumed that no coupling effect exists between the two settlement sources. In addition, this paper improves the determination of the maximum settlement location by combining calculus and curve fitting, replacing the existing prediction formula which relies heavily on engineering experience to determine the maximum settlement point. The predicted value obtained using this method comes close to the measured value, and the deviation of the maximum surface settlement value is controlled within about 5% in the three cases introduced, of which the accuracy is higher than the existing prediction formula.

The three-dimensional finite difference method was used in this study to analyze the deformation and stresses of a passive pile under surcharge load in extensively deep soft soil. A three-dimensional numerical model was proposed and verified by a field test. The horizontal displacements of the pile agreed well with the field results. This study investigated the pile-foundation soil interaction, the load transfer mechanism, the excess pore water pressure (EPWP), and the horizontal resistance of the foundation soil. The results show that the soil in the corner of the loading area developed a large uplift deformation, while the center of the loading area developed a large settlement. The lateral displacement of the pile decreased sharply with the increase of the depth and increased with the surcharge load. The lateral displacement of the soil was negligible when the depth exceeded 30 m. The EPWP increased in a nonlinear way with the increase of the surcharge load and accumulated with the placement of the new lift. The distribution of the lateral earth pressure in the shallow soil layer was complex, and the negative value was observed under a high surcharge load due to the suction effect. The proportion coefficient of the horizontal resistance coefficient showed much smaller value in the situation of large lateral deformation and high surcharge load. The design code overestimated the horizontal resistance of the shallow foundation soil, which should be given attention for the design and analysis of the laterally loaded structures in extensively soft soil.

Prestressed concrete cylinder pipe (PCCP) is widely used in hydraulic engineering. The bell‐and‐spigot joint is a weak point along a PCCP pipeline, since damage of joint can affect the operation of the whole pipeline. In this paper, a three‐dimensional numerical model of buried PCCP, considering the simulation of rubber gasket in bell‐and‐spigot joint is established. The fluid–structure coupling of PCCP is accomplished using the Mesh‐based parallel Code Coupling Interface (MpCCI), where the pipe and the surrounding soil are characterized in the software ABAQUS, and the pressurized water is modeled in the software FLUENT. The force and rotation angle at joints of PCCP under different conditions, including surcharge load, loading location, cover depth, and internal pressure, are analyzed. It is shown that the rotation angle of joint exceeds the allowable value, when the surcharge load is greater than 180 kPa. Compared with the effect of surcharge load, the offset distance (i.e., distance between the loading position and the pipe axis) has a greater influence on the development of horizontal displacement and rotation angle. As the offset distance increases, both the horizontal displacement and rotation angle at joints increase first, and they decrease after the peak. [ABSTRACT FROM AUTHOR]

This paper investigated the relative seismic response of reinforced soil retaining wall overlying a soft clayey soil layer—applicable to road or railway embankment. A series of 1D shaking table tests, 0.1 to 0.5 g, were conducted on the 1 m high physical model. The scaled physical model was subjected to harmonic sinusoidal input motions at frequencies of 1 Hz, 3 Hz, 5 Hz, 10 Hz, 12 Hz, and 15 Hz. A laminar box was used to enclose the soil during the experiment. The variation of parameters such as base motion excitations; frequencies; and surcharge pressures were studied. The results of this study revealed that these parameters have a significant influence on the model wall and vary along the elevation; impacting pore water pressure as well. It also had an impact on the variation along the depth of the clayey soil layer. Maximum face deformation was observed at the top layer of the wall. [ABSTRACT FROM AUTHOR]

This paper studies the slip surface shape of piled and no-piled slopes. Physical and numerical modelling of the foundations was performed adjacent to layered and homogenous slopes. This paper also studies the effects of pile position, surcharge distance from the slope crest, and the effects of loose layer thickness of piled and no-piled slopes on soil deformation patterns, the bearing capacity improvement ratio factor (BCR), and slope stability improvement ratio (Nps). According to the no-piled slope results, for a 0 to 2.0B dense layer distance from the ground surface, the slip surface lies on the dense layer. The soil layer angles significantly affect slope stability and footing bearing capacity. Increasing the soft bound layer angle, decreased not only the thickness of the loose sand layer, but also the soil bearing capacity and slope stability. Furthermore, increases in the surcharge load distance from 2B causes general failure of the slope, whereas lower distances allow the failure shape to be surficial. According to the tests and numerical results, the use of pile elements was provided considerable lateral movement resistance. All tests are analysed numerically and a good agreement is observed between the experimental and numerical results. [ABSTRACT FROM AUTHOR]

• A new analytical solution is proposed for lined circular tunnels subjected to surcharge loadings in semi-infinite ground. • The interaction between rigid lining and surrounding rock can be considered. • The influence of distribution forms and locations of surcharge loadings on ground responses is revealed. For tunnels located at shallow depths, the adjacent surcharge loadings caused by new building constructions or overloading on the ground surface significantly influence the stability of the tunnel and lining. This study presents a new rigorous analytical solution for the stress and displacement around lined circular tunnels at a shallow depth, fully considering the interaction between the ground and rigid lining, and any distributed surcharge loadings. A new analytical approach is provided, where the original problem is divided into two problems: Problem 1 is a semi-infinite plane subjected to surcharge loads without any holes, and Problem 2 is a tunnel contained in a semi-infinite plane loaded by the prescribed displacements along the tunnel boundary. The solutions, which strictly satisfy all the boundary and compatibility conditions of the original problem, are finally addressed by the superposition of the solutions of Problems 1 and 2 respectively obtained by the modified Flamant's solution and complex variable theory. The good agreement between the analytical and numerical results under the same assumptions verifies the correctness of the proposed analytical solutions. Furthermore, the possible deviation due to the simplification of the analytical solution is also discussed. Based on the obtained analytical solution, a parametric study is carried out to investigate the influence of the key parameters on the stress and displacement of the ground and lining. [ABSTRACT FROM AUTHOR]

Tunnels in urban areas inevitably lie near the ground surface, and will be affected significantly by the loads on the surface. This study provides a new analytical approach to efficiently predict the time-dependent ground stresses and displacements induced by shallow tunnelling under initial stresses due to both gravity and surcharge loads. The viscoelasticity of the ground, inclination of ground surface, effect of support and its delayed installation, are all taken into account. The elastic potentials were first derived for tunnels subjected to boundary stresses induced by gravity, surcharge loads and tunnel supports, respectively. Based on the extension of correspondence principle, the time-dependent ground stresses and displacements were then provided analytically for any type of linear viscoelastic ground. The FEM analysis was performed to verify the analytical solutions, which demonstrates a well agreement between the analytical and numerical results. Additionally, by the qualitative comparison of surface movements and initial failure zone around tunnel between analytical solution and results from other numerical model of elastoplastic cases, it was proved that the analytical solution can predict the initial failure zone and can qualitatively provide the reliable ground deformations. Finally, a parametric study was carried out to find the influence of timing for support installation, the slop angle and the surcharge loads on stresses and displacements around tunnels. The proposed solutions provide a quick alternative method to predict the time-dependent ground responses of shallow tunnelling in rocks, or medium/stiff clays. [ABSTRACT FROM AUTHOR]

In this study, for the establishment of a safety evaluation method, non-destructive tests were performed by developing a full-scale model pier and simulating scour on the ground adjacent to a field pier. The surcharge load (0–250 kN) was applied to the full-scale model pier to analyze the load's effect on the stability. For analyzing the pier's behavior according to the impact direction, an impact was applied in the bridge axis direction, pier length direction, and pier's outside direction. The impact height corresponded to the top of the pier. A 1-m deep scour was simulated along one side of the ground, which was adjacent to the pier foundation. The acceleration was measured using accelerometers when an impact was applied. The natural frequency, according to the impact direction and surcharge load, was calculated using a fast Fourier transform (FFT). In addition, the first mode (vibratory), second mode (vibratory), and third modes (torsion) were analyzed according to the pier behavior using the phase difference, and the effect of the scour occurrence on the natural frequency was analyzed. The first mode was most affected by the surcharge load and scour. The stability of the pier can be determined using the second mode, and the direction of the scour can be determined using the third mode. [ABSTRACT FROM AUTHOR]

In the case of sudden surcharge loading, shallow shield tunnels in areas with soft soil experience substantial deformation responses. It is very important to understand the different loading modes and control measures above the shallow shield tunnels in soft soil for improving the safety of tunnel structure and reducing the influence of deformation. In this study, a three-dimensional numerical model of shallow shield tunnels in soft soil is established with FLAC. Ground and tunnel deformations are analyzed under different loading modes, and the effects of different deformation control measures are also studied. The numerical simulations in this paper show that the surface and tunnel deformation responses vary when induced by different loading modes above shallow shield tunnels in soft soil. After surface hardening with a 20-cm-thick layer of C20 concrete, the surface settlement is effectively controlled, and the uneven longitudinal settlement of the tunnel vault is improved. However, controlling the height of the surcharge is the most direct deformation control method. When the height of the surcharge is reduced from 6 m to 4 m and 2 m, the maximum ground settlement is reduced by 37.8% and 69.4%, respectively, and the maximum longitudinal settlement of the tunnel vault is reduced by 35.3% and 65.2%, respectively. During the operation of shallow shield tunnel in soft soil area, sudden surcharge loading should not be allowed. In the inevitable case, the surcharge loading on one side of the tunnel should be prevented and the surcharge loading height should be strictly limited. [ABSTRACT FROM AUTHOR]

Stability of rock slopes is a critical issue in many mining and civil engineering projects. The current state of practice for slope stability analysis is based on obtaining the factor of safety (FOS). Stability charts are widely used by engineers to obtain a FOS for a quick assessment of the initial stability of slopes. The stability of rock slopes with vertical walls in urban areas adjacent to existing structures is another important issue in this regard. However, the stability of earth or rock slopes are usually analyzed ignoring surcharge loads. The effect of adjacent structures (as surcharge load) on slope stability (considering these loads) can be very useful in slope stability analyses in urban or even non-urban areas. In the present study, it is tried to investigate the effect of surcharge load on the stability of rock slopes based on the generalized Hoek–Brown failure criterion using a finite element numerical software and the related charts are presented. Since there is a stability chart for each slope angle, a comprehensive mathematical model utilizing artificial neural networks is proposed to predict the stability factor of rock slopes. The independent variables in this study were slope angles, slope height, the intensity of surcharge load, Geological Strength Index (GSI), and unconfined compressive strength of the intact rock. Sensitivity analysis showed that the changes in GSI, effect of surcharge and unconfined compressive strength of rock have the highest effect on the slope stability assurance coefficient. [ABSTRACT FROM AUTHOR]

Construction loads cause extra deformation and stress to nearby buried municipal pipelines. This paper investigates this issue by relating problems with inputs as free-field soil pressure or displacement by surface loading to the choice of an appropriate Winkler subgrade modulus for pipeline-soil interaction mechanisms. The theoretical analysis indicates that the input of surface load-induced soil pressures at the pipeline location results in much smaller moments and displacements of the pipeline. Although the Winkler solution using the Vesic spring modulus results in the same bending for a beam resting on the soil surface as that in elastic continuum when under a point load, its use is not always adequate for a buried pipeline with a finite embedment depth under external load and when subjected to free soil movements. An alternative expression for the spring modulus is given for a buried pipeline under a direct external load. The application of a passive Winkler modulus is proven rational when the pipeline is subjected to soil movement. A comparison between FEM analysis and the elastic continuum solution suggests that a displacement input or a coupled input be used for the analysis of a pipeline under surface loading, together with the application of a modified active Winkler modulus expression considering embedment depth and a passive Winkler modulus expression for surface loading–pipeline–soil systems under different input conditions. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering Geology / Gongcheng Dizhi Xuebao is the property of Journal of Engineering Geology 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.)

In this study, for the establishment of a safety evaluation method, non-destructive tests were performed by developing a full-scale model pier and simulating scour on the ground adjacent to a field pier. The surcharge load (0–250 kN) was applied to the full-scale model pier to analyze the load’s effect on the stability. For analyzing the pier’s behavior according to the impact direction, an impact was applied in the bridge axis direction, pier length direction, and pier’s outside direction. The impact height corresponded to the top of the pier. A 1-m deep scour was simulated along one side of the ground, which was adjacent to the pier foundation. The acceleration was measured using accelerometers when an impact was applied. The natural frequency, according to the impact direction and surcharge load, was calculated using a fast Fourier transform (FFT). In addition, the first mode (vibratory), second mode (vibratory), and third modes (torsion) were analyzed according to the pier behavior using the phase difference, and the effect of the scour occurrence on the natural frequency was analyzed. The first mode was most affected by the surcharge load and scour. The stability of the pier can be determined using the second mode, and the direction of the scour can be determined using the third mode.

Summary: The construction of twin tunnels at shallow depth has become increasingly common in urban areas. In general, twin tunnels are usually near each other, in which the interaction between tunnels is too significant to be ignored on their stability. The equivalent arbitrarily distributed loads imposed on ground surface were considered in this study, and a new analytical approach was provided to efficiently predict the elastic stresses and displacements around the twin tunnels. The interaction between 2 tunnels of different radii with various arrangements was taken into account in the analysis. We used the Schwartz alternating method in this study to reduce the twin‐tunnel problem to a series of problems where only 1 tunnel was contained in half‐plane. The convergent and highly accurate analytical solutions were achieved by superposing the solutions of the reduced single‐tunnel problems. The analytical solutions were then verified by the good agreement between analytical and numerical results. Furthermore, by the comparison on initial plastic zone and surface settlement between analytical solution and numerical/measured results of elastoplastic cases, it was proven that the analytical solution can accurately predict the initial plastic zone and its propagation direction and can qualitatively provide the reliable ground settlements. A parametric study was finally performed to investigate the influence of locations of surcharge load and the tunnel arrangement on the ground stresses and displacements. The new solution proposed in this study provides an insight into the interaction of shallow twin tunnels under surcharge loads, and it can be used as an alternative approach for the preliminary design of future shallow tunnels excavated in rock or medium/stiff clay. [ABSTRACT FROM AUTHOR]

Tunnels in urban areas inevitably lie near the ground surface, and will be affected significantly by the loads on the surface. In this study, a new analytical solution is presented for the first time, by means of which the ground responses around circular shallow tunnels subjected to surcharge loadings can be quickly predicted. The ground is approximately assumed as an elastic or viscoelastic medium, and arbitrary distribution of surcharge loads, as well as any viscoelastic models, are accounted for. Case (A) is modelled with surcharge loads applied before the tunnel excavation. The incremental elastic displacements and stresses which occur after the tunnel excavation are provided by Verruijt’s method, combined with a Fourier expansion of the tractions. Case (B) represents the model in which the surcharge loads are applied after the tunnel excavation, and the elastic ground responses due to the presence of surcharge load are proposed by the superposition of modified Flamant’s solutions and the solution of Case (A). The solutions for the viscoelastic problem of the two cases are also proposed by an extended corresponding principle, taking into account the time-dependence of the rock/soil with any types of the linear viscoelastic model. All of these analytical solutions are verified by good agreements of the comparison between the analytical solutions and FEM results. Furthermore, they are consistent with measured data qualitatively. Finally, a parametric study is carried out to investigate the influence of the uniform surcharge load on the stresses and displacements of the ground in the two cases. The proposed new solutions potentially provide an alternative approach in the preliminary designs of future shallow tunnels. [ABSTRACT FROM AUTHOR]

Slope stability analysis generally considers a homogeneous slope composed of either soil or rock. There is no definitive criterion to distinguish homogeneous and heterogeneous slopes. This paper presents five model tests on two-layered slopes with different interface subjected to surcharge load. Numerical simulations were performed to capture the behaviors observed. Given the satisfactory reproduction of the model tests, a parametric study was then conducted to investigate the impact of the interface, slope angle and strength parameters. Finally, a set of criteria based on the relative cohesion ratio was proposed to characterize a distinct change in the nature of the slope. [ABSTRACT FROM AUTHOR]

The available analytical methods are inadequate to quantify the displacement of embedded cantilever retaining (ECR) walls in working conditions owing to the intricacies present in the problem. The complexity of the problem further increases in the presence of a surface surcharge loading because, the loading intensity, width of the strip, and its distance from the wall significantly influence the wall behavior. This article presents an analytical method for the displacement-controlled analysis of rigid ECR walls in cohesionless soils, with a uniform strip surcharge placed on the backfill surface. The proposed method can be used to calculate the required embedment depth and the structural forces of an ECR wall while the wall displacement is prescribed. Alternatively, the wall displacement can be determined when the embedment depth, retaining height, and surcharge pressures are given. A displacement-dependent earth pressure mobilization approach is used to derive the soil pressures on the wall. Surcharge load-induced additional earth pressure on the wall is derived by adopting a suitable load distribution in the subsurface. The embedment depth of the wall is determined by assuming rigid rotation of the wall and satisfying the horizontal force and moment equilibrium. Analytical expressions are provided to calculate the bending moment distribution and the ground settlement profile behind the wall. The analytical results are compared with those of the numerical analyses performed in PLAXIS 2D. A parametric study was carried out to investigate the influence of the surcharge loading intensity, width of the strip, its distance from the wall, soil friction angle, wall roughness on the wall displacement and bending moment. [ABSTRACT FROM AUTHOR]

The couple effect of soil displacement and axial load on the single inclined pile in cases of surcharge load and uniform soil movement is discussed in detail with the methods of full-scale field tests and finite element method. Parametric analyses including the degree of inclination and the distance between soil and pile are carried out herein. When the displacement of soil on the left side and right side of a pile is identical, deformation of a vertical pile and an inclined pile is highly close in both cases of surcharge load and uniform soil movement. When the couple effect of soil displacement and axial load occurs, settlement of an inclined pile is greater than that of a vertical pile under the same axial load, and bearing capacity of an inclined pile is smaller than that of a vertical pile. This is quite different from the case when the inclined pile is not affected by soil displacement. For inclined piles, P- Δ effect of axial load would lead to a large increase in bending moment, however, for the vertical pile, P- Δ effect of axial load can be neglected. Although the direction of inclination of piles is reverse, deformation of piles caused by uniform soil movement is totally the same. For the inclined piles discussed herein, bending moment (−8 m to −17 m under the ground) relies heavily on uniform soil movement and does not change during the process of applying axial load. When the thickness of soil is less than the pile length, the greater the thickness of soil, the larger the bending moment at lower part of the inclined pile. When the thickness of soil is larger than the pile length, bending moment at lower part of the inclined pile is zero. [ABSTRACT FROM AUTHOR]

Effect of soil displacement on friction single pile in the cases of tunneling, surcharge load and uniform soil movement was discussed in details with finite element method. Lateral displacement of the pile caused by soil displacement reached about 90% of the total displacement, which means that P-Δ effect of axial load can be neglected. The maximum moment of pile decreased from 159 kN·m to 133 kN·m in the case of surcharge load when the axial load increased from 0 to the ultimate load. When deformation of pile caused by soil displacement is large, axial load applied on pile-head plays the role of reducing the maximum bending moment in concrete pile to some extent. When pile is on one side of the tunnel, soil displacements around the pile are all alike, which means that the soil pressures around the pile do not decrease during tunneling. Therefore, Q-s curve of the pile affected by tunneling is very close to that of pile in static loading test. Bearing capacities of piles influenced by surcharge load and uniform soil movement are 2480 kN and 2630 kN, respectively, which are a little greater than that of the pile in static loading test (2400 kN). Soil pressures along pile increase due to surcharge load and uniform soil movement, and so do the shaft resistances along pile, as a result, when rebars in concrete piles are enough, bearing capacity of pile affected by soil displacement increases compared with that of pile in static loading test. [ABSTRACT FROM AUTHOR]