Liquefaction-induced Lateral Deformation Research Articles

Liquefaction-Induced Lateral Spreading Mitigation Using Pervious Concrete Column Inclusion in Sloping Strata

ABSTRACT The effectiveness of pervious concrete column remediation in homogeneous and sandwiched soil strata for mitigating liquefaction-induced lateral spreading is being investigated in this study. The seismic performance of pervious concrete column improved ground is compared with stone column improved ground. The efficacy of pervious concrete column on three types of soil strata in mitigating liquefaction along with the parameters influencing ground lateral deformation such as thickness of sandwiched liquefiable soil layer, permeability of surrounding soil, ground surface inclination, peak ground acceleration and surcharge load are reported. Three-dimensional nonlinear finite element software OpenSeesPL is used to analyze remediated ground with stone column and pervious concrete column inclusions. Liquefaction-induced lateral deformation is found to be lesser in pervious concrete column improved ground in comparison with stone column improved ground. The lateral deformation of pervious concrete column remediated ground is found to be independent of surrounding soil permeability. The pervious concrete column inclusion is found to be a better alternative to stone column in mitigating liquefaction in susceptible soils like loose sand, medium-dense sand, silt strata and sandwiched liquefiable soil deposits.

A shaking table-based experimental study of seismic response of shield-enlarge-dig type's underground subway station in liquefiable ground

In instances where earthquakes with large magnitude occur, liquefaction-induced lateral deformation of ground has caused thorough destruction to the underground structure of urban rail transit. A sequence of shaking table experiments was conducted on shield-enlarge-dig type's subway station structure in liquefiable ground exposed to the near field earthquake and the far field earthquake. Outcomes of these experiments are discussed in items of foundation deformation, pore water pressure, acceleration response, dynamic soil pressure, and macroscopic failure of model structure. The measured data infers that, when subjected to a high intensity earthquake, the model structure generates an upward movement relative to the foundation. The difference between the soil pressure above and below the structure is the internal cause of the liquefaction-induced uplift of the structure. The shear deformation to the soil layer of the foundation happened, and the displacement peak values of the left and right pendula were asymmetric. The acceleration response and its amplification coefficient in the model foundation gradually increases towards the surface from the bottom as a result of a low intensity earthquake, but for medium and high intensity earthquakes, the acceleration response decreases first and then increases. A notable phenomenon of high frequency filtering and low frequency amplification ensued during the seismic wave propagation from the bottom to the surface of soil. For the same depth of measuring points in foundation soil, the time when the pore-pressure ratio reaches the peak lags behind the time when the acceleration reaches the peak, and the hysteresis is more intense with a rise in magnitude of ground movement. The response spectrum of a low intensity earthquake is characterized by low period accumulation and amplification, while the response spectrum of medium and high intensity is characterized by moves from short period to long period and multi-peaks. The pore pressure accumulation of the model foundation experienced a change process of “rapid growth and slow dissipation,” and the time period of its sharp increase was consistent with that of the sharp increase of the acceleration arias strength. The existence of the underground structure notably inhibits an increase in pore water pressure. The earthquake damage mechanism of the underground subway station of shield-enlarge-dig type in liquefiable ground occurred in three phases: shear failure occurred on the column and damaged the opening position and spandrel of the tunnel; connection parts of the side wall and roof exhibited tensile damage; and the underground structure collapsed.

A multilateral analysis of slope failure due to liquefaction-induced lateral deformation using shaking table tests

Liquefaction-induced lateral displacement can cause substantial deformations and trigger failure in the saturated sandy slopes. This study elaborates on the results of a shaking table experiment performed on a saturated sandy slope model. A transparent Plexiglass container was used to allow visualization of the time-dependent ground displacements at different grid points. Using colored sand grid along with the video-tracking analysis technique provided an excellent opportunity for instant monitoring of the model deformation in both the time and space domains. Furthermore, the pore pressure buildup and dissipation in the soil medium and acceleration time histories of the model were recorded and analyzed. Detailed and comprehensive analyses of the high-resolution recorded data streams resulted in the determination of the onset of liquefaction and the induced subsidence, acceleration response, deformation behavior, and shear strain progress through time and depth at different slope sections. It was also found that the shear strain rate was different in the on-slope and free field locations, and its value was proportional to the liquefaction duration. It was also observed that the variation of the shear strain rate at different depths in the free field led to a localized sliding event.

Centrifuge modeling of batter pile foundations in laterally spreading soil

Batter piles are widely used in geotechnical engineering construction. Observations regarding the performance of batter piles in seismic hazards are controversial, and few studies have evaluated batter piles in liquefiable and laterally spreading ground. Three centrifuge experiments were performed to gain a better understanding of the performance of batter piles in liquefiable ground and to reveal the influence of the overlying nonliquefiable layer on the batter pile foundation design. The results reveal that for symmetrically placed batter piles, the bending moment of the front pile is greater than that of the rear pile, as a result of the liquefaction-induced lateral deformation in all three cases, and the bending moment reaches its maximum value at the middle of the pile. The presence of the overlying nonliquefiable dense sand layer reduces the potential for liquefaction and lateral spreading of the underlying ground, the settlement and bending moments of the batter piles.

Simplified dynamic analysis to evaluate liquefaction-induced lateral deformation of earth slopes: a computational fluid dynamics approach

Lateral deformation of liquefiable soil is a cause of much damage during earthquakes, reportedly more than other forms of liquefaction-induced ground failures. Researchers have presented studies in which the liquefied soil is considered as viscous fluid. In this manner, the liquefied soil behaves as non-Newtonian fluid, whose viscosity decreases as the shear strain rate increases. The current study incorporates computational fluid dynamics to propose a simplified dynamic analysis for the liquefaction-induced lateral deformation of earth slopes. The numerical procedure involves a quasi-linear elastic model for small to moderate strains and a Bingham fluid model for large strain states during liquefaction. An iterative procedure is considered to estimate the strain-compatible shear stiffness of soil. The post-liquefaction residual strength of soil is considered as the initial Bingham viscosity. Performance of the numerical procedure is examined by using the results of centrifuge model and shaking table tests together with some field observations of lateral ground deformation. The results demonstrate that the proposed procedure predicts the time history of lateral ground deformation with a reasonable degree of precision.

Countermeasures Assessment of Liquefaction-Induced Lateral Deformation in a Slope Ground System

Liquefaction-induced lateral spreading may result in significant damage and disruption of functionality for structures and Slope Ground System. In this regard, finite-element simulations are increasingly providing a versatile environment in order to assess economical and effective countermeasures. Several systematic bidimensional FEM computations have been conducted to evaluate mitigation strategies under the action of an applied earthquake excitation. The presented study highlights the potential of computations in providing insights for analysis of liquefaction-induced lateral deformations. In the analysis, some specific assumptions are introduced and verified such as a nine-node quadrilateral elements, massive columns of soil with periodic boundary conditions, and a Lysmer-Kuhlemeyer dashpot used to model the finite rigidity of the underlying elastic medium. Moreover, the study aims to systematically explore the effectiveness of densification as a countermeasure and then evaluate the best extension comparing two scenarios.

Mitigation of Liquefaction-Induced Lateral Deformation in a Sloping Stratum: Three-dimensional Numerical Simulation

Finite-element (FE) simulations are increasingly providing a versatile environment for conducting lateral ground deformation studies. In this environment, mitigation strategies may be assessed in order to achieve economical and effective solutions. On the basis of a systematic parametric study, three-dimensional FE simulations are conducted to evaluate mitigation by the stone column (SC) and the pile-pinning approaches. Mildly sloping saturated cohesionless strata are investigated under the action of an applied earthquake excitation. For that purpose, the open-source computational platform OpenSees is employed, through a robust user interface that simplifies the effort-intensive pre- and postprocessing phases. The extent of deployed remediation and effect of the installed SC permeability are investigated. The influence of mesh resolution is also addressed. Generally, SC remediation was found to be effective in reducing the sand stratum lateral deformation. For a similar stratum with permeability in the silt range, SC remediation was highly ineffective. In contrast, pile pinning appeared to be equally effective for the sand and silt strata permeability scenarios. Overall, the conducted study highlights the potential of computations for providing insights toward the process of defining a reliable remediation solution.