International Journal of Geomechanics

A geofoam was produced by blending expanded polystyrene (EPS) beads and sands in proportions. The formed mixtures, known as EPS-sands, were 26–63% lighter than general earth fills (e.g., sand). Consolidated-drained (CD) triaxial compression tests were conducted on EPS-sand mixture specimens to observe their stress-strain characteristics, specifically, the stress-strain responses in relation to the EPS contents (0.5, 1.5, and 2.5% by weight) used in the mixtures and confining pressures (100, 200, 300 to 400 kPa) loaded on the specimens. The EPS content and confining pressure were found to influence the stress-strain and volumetric strain behavior of the mixtures. Increasing EPS content led to decreased shear strength and increased volumetric strain. Increasing confining pressures enhanced the strength of the mixture. EPS-sand mixtures underwent a shear contraction throughout the CD tests. The optimum EPS bead content (i.e., the one reasonably balancing the unit weight, strength, and deformation) was in the order of 0.5% by weight. EPS content dependent strain increment equations were derived by compromising Cam-clay and modified Cam-clay, and used to model the stress-strain characteristics of EPS-sand mixtures. The established equations were verified being able to depict the stress-strain observations of EPS-sand specimens, at least for the ranges of EPS contents and confinements considered in this study.

An inclined eight-story reinforced concrete building on a thick soft clay deposit was leveled by compensation grouting with short gel time grout injected through sleeved pipes. The monitoring system is used to record the injected grout volume, the mat foundation’s heaved volume after grouting, and the mat foundation’s settled volume during pore pressure dissipation. The grouting efficiencies improved from negative value to less than one, and the stress histories of clay soils changed from normally consolidated to overconsolidated states. A final compensation efficiency of 9.78% was achieved and the building was successfully leveled. A series of numerical simulations were conducted to assess the capability of compensation grouting modeling. The numerical simulation results indicate that the consolidation behavior and the stress history of clayey foundation soils can be modeled reasonably well. However, the computed final grout efficiency is larger than that from the monitoring data because the simulation of fracture grouting by volumetric strain input is more like compaction grouting mode rather than fracture grouting mode, and this induces lesser excess pore pressure, lesser settlement and higher grout efficiency. These findings are also confirmed from other researchers’ laboratory and field testing results.

As a permeable base material of pavement, the large stone porous asphalt mixture (LSPM) is used widely in China to lessen the moisture damage of the asphalt pavement. However, the dynamics mechanism of the inhibitory effect of permeable base on moisture damage is not clear yet. The dynamic fluid-solid coupling analysis of the saturated pavement with LSPM base course, considering the asphalt mixtures as the porous medium, was performed using the finite difference numerical code FLAC3D. Numerical results revealed that the positive and negative dynamic pore pressure alternated in the pavement with the approaching and leaving of the wheel loads. The phenomenon of water pumping out of and sucking into the pavement under the moving loads was proved. The flow of fluid in pavement can be regarded as the laminar flow. The presence of the LSPM base course greatly decreased the dynamic pore pressure and the scouring force in the surface course because of the large permeability coefficient of the LSPM. The location of the maximum dynamic pore pressure also changed due to the LSPM base course. Due to the permeable base, the dissipation of the dynamic pore pressure was accelerated and thus the moisture damage was lessened.

Finite-element analysis on a pavement structure under traffic loads has been a viable option for researchers and designers in highway pavement design and analysis. Most of the constitutive drivers used were nonlinear elastic models defined by empirical resilient modulus equations. Few isotropic/kinematic hardening elastoplastic models were used but applying thousands of repeated load cycles became computationally expensive. In this paper, a cyclic plasticity model based on fuzzy plasticity theory is presented to model the long-term behavior of unbound granular materials under repeated loads. The discussion focuses on the model parameters that control long-term behavior such as elastic shakedown. The performance of the constitutive model is presented by comparing modeled and measured permanent strain at various numbers of load cycles. Calculated resilient modulus from the complete stress-strain curve is also discussed.

Two methods of upper bound solutions were used to calculate the needed support pressure ${\sigma }_T$ for shallow tunnel stability in cohesive-frictional ground. One uses a proposed rigid blocks failure mechanism for shallow rectangular tunnel of upper bound solution, and another uses a finite-element upper bound solution with linear program. In the rigid blocks failure mechanism, the velocity discontinuities in the side wall of the shallow rectangular tunnel occurred in both radial and tangent directions, so as to increase its flexibility. The main formulas for calculating support pressure ${\sigma }_T$ were deduced for the above two methods; thereafter, the corresponding calculating programs were compiled. The needed support pressure ${\sigma }_T$ for shallow tunnel stability and its parametric influences were obtained. The results show that both methods can be used effectively to analyze the stability problems of shallow rectangular tunnel using upper bound solutions.