Location Of Failure Surface Research Articles

Upper-bound solutions for the soil thrust of clay under a track system in 3D conditions

This study proposes a quick and reliable method for estimating the soil thrust in clay ground for a tracked vehicle based on limit analysis in three-dimensional conditions. With respect to the shape and location of failure surfaces in clayey ground, block, triangular wedge, and trapezoidal wedge failure modes were considered. Between the upper-bound solutions from the different failure modes, the least upper-bound solution was proposed as the soil thrust. To verify the proposed solution, it was compared to the model test and numerical simulations for a track system over model clay ground. The proposed upper-bound solution is expected to produce a reliable soil thrust quickly in real time, especially for submerged heavy-weight remotely operated vehicles (ROVs).

Three-dimensional limit analysis of seismic stability of tunnel faces with quasi-static method

Based on the existing research results, a three-dimensional failure mechanism of tunnel face was constructed. The dynamic seismic effect was taken into account on the basis of quasi-static method, and the nonlinear Mohr-Coulomb failure criterion was introduced into the limit analysis by using the tangent technique. The collapse pressure along with the failure scope of tunnel face was obtained through nonlinear limit analysis. Results show that nonlinear coefficient and initial cohesion have a significant impact on the collapse pressure and failure zone. However, horizontal seismic coefficient and vertical seismic proportional coefficient merely affect the collapse pressure and the location of failure surface. And their influences on the volume and height of failure mechanism are not obvious. By virtue of reliability theory, the influences of horizontal and vertical seismic forces on supporting pressure were discussed. Meanwhile, safety factors and supporting pressures with respect to 3 different safety levels are also obtained, which may provide references to seismic design of tunnels.

The New Method to Evaluate the Uplift Capacity of Belled Piles in Sandy Soil

In conventional geotechnical engineering, the pull out of pile is always blamed only on the shear failure of the soil caused by the uplift force developed from the tip of the pile. For the belled pile, however, the enlarged foundation plays an important role to against the compression/uplift load, and the current theories for estimating the uplift capacities of the pile were found more than 50% relative error from measured. In this study, a new method for estimating the ultimate uplift capacity of the belled pile embedded in sandy soil was developed by taking into account the elastic/plastic behavior of the soil around the belled pile. It assumes that during the pull out process of the pile, the soil above the enlarged base is firstly subjected to an upward compression and causes a local soil consolidation which might affect the development of resultant failure surface of the soil around the pile. The starting location of failure surface is allowed to develop at a distance away from the pile surface. With 37 sets of experimental/field tests data, the development of the failure surface with curved slip-surface was suggested to start at the location of 0.67 of the radius of the enlarged base from central axis of the pile. The new method shows good approach with relative error lesser than 25% which is better than previous theories.

Application of FEM Strength Reduction Dynamic Analysis in the Seismic Design of Reinforced Earth-Retaining Wall with Geo-Grid

Due to the special mesh structure, geo-grid material can avoid local subsidence of filling material, reduce uneven settlement of soil mass to the largest degree and improve the whole stability of soil mass, so the reinforced earth-retaining wall with geo-grid is widely used in engineering. Meanwhile, researches on its dynamic characters are not enough and it is hard to judge the whole stability of reinforced earth-retaining wall under seismic condition. When unstable failure happens, the location of failure surface can hardly be identified. These disadvantages have seriously limited the development of this supporting method and cause unsafe potentials for engineering. Based on the FEM strength reduction dynamic analysis and combined with practical engineering, the paper conducts stability analysis on the reinforced earth-retaining wall of geo-grid under seismic condition and the research achievements provide a new thinking for the seismic design of reinforced earth-retaining wall with geo-grid.

Coupled Elastoplastic Analysis of Dam Seismic Stability

A nonlinear procedure for coupled elastoplastic analysis of the dam seismic stability was presented in this paper. The soil nonlinear dynamic behavior was modeled using by a multiple yield surface model based on the numerical framework of u-p formulation. The strength reduction method was used to determine the factor of safety of dam slope and the location of failure surface. A case study of a 293.5 m high clay core rockfill dam was used to demonstrate the application of the method. Based on the computed results, it is founded that the maximum acceleration amplification coefficient is 1.72, which is almost 20% less than that obtained from the equivalent linear analysis. The most dangerous slip surface was at the shallow zone of the lower part of the upstream slope, which was different from the predicted location from the equivalent linear analysis. The earthquake induced pore water pressure and permanent deformation were also studied in detail.

Influence Zones in Alluvium Over Dip‐Slip Faults

Tests were performed on dense and loose sand in a glass‐walled fault test box to investigate the shapes and locations of failure surfaces that may occur in alluvium overlying active dip‐slip faults. The experimental procedure is reviewed and the results of the tests with reverse and with normal movements along the bedrock faults are presented. Based on the experimental results, a simple model is developed to predict the shapes and locations of failure surfaces in the soil. These are determined as a function of the depth of the soil, the angle of dilation for the soil, and the dip angle of the fault. The conditions for development of a graben structure, as observed during normal movement on the bedrock fault, are also determined. The emphasis of the study is on the mechanics of deformation and failure in cohesionless soil above dip‐slip faults in relation to principles of soil mechanics. The simple model is also evaluated in relation to real field conditions.

Multiple Failure Surfaces Over Dip‐Slip Faults

The shapes and locations of failure surfaces in alluvium overlying active dipslip faults are studied on the basis of experiments performed in a fault test box. A simple model for predicting primary...