International Journal of Geomechanics

Major civil engineering structures are being constructed now a days in complex geological environment with faults, shear zones, and other major discontinuities. These major discontinuities can cause a variety of problems in both surface and underground constructions. Unfavorably dipping major discontinuities may create unstable conditions in underground openings and contribute to the deformations of a rock mass under external static loading. Hence, rock–structure interaction analysis should simulate arbitrarily oriented rough and undulating major discontinuities within the rock mass, as well as the undulating interface along the structure and the rock mass such as dam foundations and underground excavations intersected by fault/shear zones. Realistic simulation of the mechanical behavior of rock joints is a prerequisite for successful numerical modeling of discontinuous rocks. When joint modeling is designed to include different degrees of joint roughness, dilation, and aperture, then realistic response depends upon the appropriate constitutive models and the way these parameters interact with stress change. Due to low values of the normal and tangential module, a unique characteristic of a rock discontinuity is that dilation may occur as soon as relative slip takes place and this may significantly alter the stress distribution, particularly around an underground excavation. In view of these practical requirements, a generalized formulation of a three-dimensional joint/interface element has been proposed here to account for dilatancy, roughness, and undulating surface of discontinuities.

A numerical model was developed to simulate the response of two instrumented, centrifuge model tests on soft clay and to investigate the factors that affect the seismic ground response. The centrifuge tests simulated the behavior of a rectangular building on $30\mathrm{m}$ uniform and layered soft soils. Each test model was subjected to several earthquakelike shaking events at a centrifugal acceleration level of $80g$ . The applied loading involved scaled versions of an artificial western Canada earthquake and the Port Island ground motion recorded during the 1995 Kobe Earthquake. The centrifuge model was simulated with the three-dimensional finite-difference-based fast Lagrangian analysis of continua program. The results predicted with the use of nonlinear elastic–plastic model for the soil are shown to be in good agreement with measured acceleration, soil response, and structural behavior. The validated model was used to study the effect of soil layering, depth, soil–structure interaction, and embedment effects on foundation motion.

In this paper an analytical method has been proposed to predict the net ultimate uplift capacity of pile groups embedded in sand considering the arching effect. This method takes into consideration the embedded length $\left(L\right)$ , diameter of the pile $\left(d\right)$ , surface characteristics of pile, group configuration, spacing of the pile group ( $3d$ to $6d$ ), and the soil properties. Arching develops due to relative compressibility of sand relative to pile which activates the soil–pile friction. As piles/pile groups move up, the active state of soil is initiated. The modified value of active earth pressure coefficient considering arching effect has been derived. Typical charts for evaluation of net ultimate uplift capacity for pile groups are presented through the figures. The predicted values of ultimate uplift capacity of pile groups with different configuration and slenderness ratios are compared with the available experimental results. The predicted values considering arching effect are found to be in good agreement with the data available from the literature.

In this study, an attempt is made to analyze the extent of the smear zone caused by mandrel driven vertical drains, employing the cavity expansion theory for soft clay obeying the modified Cam-clay model. The predictions are verified by large-scale laboratory tests, where the extent of the smear zone was estimated based on the indications, such as the pore pressure generated during mandrel driving, change in lateral permeability, and the water content reduction. This study reveals that the radius of smear zone is about 4–6 times the equivalent vertical drain radius, and the lateral permeability (inside the smear zone) is 61–92% of that of the outer undisturbed zone. Finally, the predicted size of the smear zone using the undrained cavity expansion solution is incorporated in the finite-element code PLAXIS to study the performance of a test embankment selected from the Sunshine Motorway, Queensland, Australia. A good agreement between the predicted values and field measurements was found.