Showing papers in "International Journal of Geomechanics in 2010"

Experimental and Numerical Study of Railway Ballast Behavior under Cyclic Loading

Abstract: This paper presents the results of the influence of frequency on the permanent deformation and degradation behavior of ballast during cyclic loading. The behavior of ballast under numerous cycles was investigated through a series of large-scale cyclic triaxial tests. The tests were conducted at frequencies ranging from 10–40 Hz, which is equivalent to a train traveling from 73 km/h to 291 km/h over standard gauge tracks in Australia. The results showed that permanent deformation and degradation of ballast increased with the frequency of loading and number of cycles. Much of breakage occurs during the initial cycle; however, there exists a frequency zone of 20 Hz⩽f⩽30 Hz where cyclic densification takes place without much additional breakage. An empirical relationship among axial strain, frequency and number of cycles has been proposed based on the experimental data. In addition, discrete-element method (DEM) simulations were carried out using PFC2D on an assembly of irregular shaped particles. A novel app...

Determining Hardness and Elastic Modulus of Asphalt by Nanoindentation

Abstract: Nanoindentation is a relatively new technique which has been used to measure nanomechanical properties of surface layers of bulk materials and of thin films. In this study, micromechanical properties such as hardness and Young’s modulus of asphalt binders and asphalt concrete are determined by nanoindentation experiments. Indentation tests are conducted on a base binder and two polymer-modified performance grade (PG) binders such as PG-70-22 and PG76-28. In addition, two Superpave asphalt mixes such as SP-B and SP-III are designed using these PG binders, and the corresponding mixes are compacted to prepare asphalt concrete. Aggregate, matrix (Materials Passing No. 4 sieve) and mastic (Materials Passing No. 200 sieve) phases of each asphalt concrete sample are indented using both Berkovich and Spherical indenters. In nanoindentation, an indenter penetrates into asphalt material and the load (milli-Newton) and the depth (nanometers) of indentation are recorded continuously. Indentation load versus displacem...

Neural Network Modeling of Resilient Modulus Using Routine Subgrade Soil Properties

Abstract: Artificial neural network (ANN) models are developed in this study to correlate resilient modulus with routine properties of subgrade soils and state of stress for pavement design application. A database is developed containing grain size distribution, Atterberg limits, standard Proctor, unconfined compression, and resilient modulus results for 97 soils from 16 different counties in Oklahoma. Of these, 63 soils (development data set) are used in training, and the remaining 34 soils (evaluation data set) from two different counties are used in the evaluation of the developed models. A commercial software, STATISTICA 7.1, is used to develop four different feedforward-type ANN models: linear network, general regression neural network, radial basis function network, and multilayer perceptrons network (MLPN). In each of these models, the input layer consists of seven nodes, one node for each of the independent variables, namely moisture content (w) , dry density ( γd ) , plasticity index (PI), percent passing ...

Nonlocal Multilaminate Model for Strain Softening Analysis

Abstract: A constitutive model formulated within the multilaminate framework is described in this paper. The basic model, incorporating deviatoric and volumetric hardening, was developed for normally consolidated or slightly overconsolidated clay. This model has been extended to account for shear softening by using a nonlocal formulation. The nonlocal plasticity is based on weighted average of plastic strains taken from neighboring material points within a certain distance which is a function of an internal length parameter. This parameter is related to the mean grain size that restricts the element size. By using a softening scaling this restriction can be eliminated and the model is therefore capable of simulating geotechnical boundary value problems. The capability of the model for simulating strain softening behavior is shown by numerical simulation of biaxial tests. Finally, the ground response curve obtained from the proposed model for excavation of a tunnel in soil is discussed.

Analysis of soil disturbance associated with mandrel-driven prefabricated vertical drains using an elliptical cavity expansion theory

Abstract: The installation of mandrel-driven prefabricated vertical drains and resulting disturbance of soft saturated clays are analyzed with a new elliptical cavity expansion theory. This formulated theory accounts for a concentric progression of elliptical cavities in an undrained condition and the large-strain effects in the plastic zone incorporating the modified Cam clay parameters. The total and effective stresses and excess pore water pressure in the soils surrounding the mandrel are predicted taking into account the mandrel installation rate, mandrel dimensions and the time factor. The theoretical variation of excess pore pressure is then compared with the results of large-scale consolidometer tests, which show that the estimated and measured pore pressures are almost the same. The plastic shear strain normalized by the rigidity index is then used to identify the zone of disturbance around the vertical drains. This formulation has been applied to a case history from the Muar clay region in Malaysia, and th...

Consolidation beneath Circular Skirted Foundations

Abstract: The effect of foundation embedment on consolidation has not been considered previously in a systematic manner, although this is of particular interest for offshore foundations, where embedment is provided by skirts that enclose a compressible soil plug. For skirted foundations, critical uncertainties include what to assume in terms of the degree of drainage at skirt tip level, and the relative time scales of consolidation within the soil plug and beneath the foundation. In this paper, results from small strain finite-element analyses are used to quantify the immediate and time-dependent response of circular skirted foundations to uniaxial vertical loading. Foundations with frictionless and fully rough skirt-soil interfaces with varying ratio of embedment depth to foundation diameter are considered and the responses compared with those for surface foundations. The findings show that both skirt-soil interface roughness and embedment ratio have a significant effect on the consolidation response.

Failure mechanisms of pile foundations in liquefiable soil: parametric study.

Abstract: This paper presents the response of piles in liquefiable soil under seismic loads. The effects of soil, pile, and earthquake parameters on the two potential pile failure mechanisms, bending and buckling, are examined. The analysis is conducted using a two-dimensional plain strain finite difference program considering a nonlinear constitutive model for soil liquefaction, strength reduction, and pile-soil interaction. The depths of liquefaction, maximum lateral displacement, and maximum pile bending moment are obtained for concrete and steel piles for different soil relative densities, pile diameters, earthquake predominant frequencies, and peak accelerations. The potential failure mechanisms of piles identified from the parametric analysis are discussed.

Seismic Rotational Displacements of Gravity Walls by Pseudodynamic Method with Curved Rupture Surface

Abstract: This paper presents the use of pseudodynamic method to compute the rotational displacements of gravity retaining walls under passive condition when subjected to seismic loads. The concept of Newmark sliding block method for computing the rotational displacements under seismic condition and the limit equilibrium analysis have been combined in this paper to evaluate the performance of a gravity retaining walls under seismic conditions. One of the main features of the paper is the adoption of a new procedure to evaluate seismic passive earth pressure considering composite curved rupture surface (which is the combination of arc of a logarithmic spiral and straight line) and the dynamic nature of earthquake loading, which is useful to predict rotational displacements accurately. It also determines the threshold seismic acceleration coefficients for rotation using Newmark’s sliding block method. It is shown that the assumption of planar failure mechanism for rough soil-wall interfaces significantly overestimate...

Stability of Shallow Tunnel Using Rigid Blocks and Finite-Element Upper Bound Solutions

Abstract: Two methods of upper bound solutions were used to calculate the needed support pressure σT 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 σT were deduced for the above two methods; thereafter, the corresponding calculating programs were compiled. The needed support pressure σT 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.

Measuring and Modeling Proportion-Dependent Stress-Strain Behavior of EPS-Sand Mixture

Abstract: 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.

Can Soil Arching Be Insensitive to ϕ

Abstract: Arching is a common phenomenon that is encountered in backfilling behind retaining walls, trenches, or underground voids in the mine. Marston’s equation has been widely used and modified for computing stresses within backfills, duly accounting for the reduction in stresses due to arching. A critical appraisal of Marston’s equation and its improved forms reveal that the average vertical stress within the soil backfill at any depth is governed by the product of earth pressure coefficient K and wall-backfill frictional coefficient μ , which does not vary significantly with variation in friction angle ϕ of the granular soil backfill. The average normal stress depends on the value assumed for δ/ϕ and whether the lateral earth pressure coefficient has been assumed as Ka , K0 , or KKrynine . Therefore, it is not necessary to direct any effort toward determining the friction angle of the backfill precisely. Rather, attention should be paid to the value of δ/ϕ and the appropriate expression for K . Thus, it can be...

Large Deformation Finite-Element Analysis of Submarine Landslide Interaction with Embedded Pipelines

Abstract: Submarine landslides represent one of the most significant geohazards on the continental slope in respect of the risk they pose to infrastructure such as deep water pipelines. A numerical approach, based on the finite-element method but using remeshing, was established in this paper to simulate large flow deformation of debris from a landslide and to quantify the loads and displacements imposed on pipelines embedded in the seabed. A simple two-dimensional elastic perfectly plastic soil model with plane strain conditions was employed in this analysis. The pipeline was restrained by a set of springs so that the load on the pipeline built up to a stable value, representing the limiting load at which the debris flowed over the pipeline. A parametric study was undertaken by varying the pipeline embedment and the relative strengths of the debris and seabed. The analysis results show that the various combinations of soil strength and embedment depth lead to different debris-pipeline movement patterns and consequ...

Site Characterization Model Using Artificial Neural Network and Kriging

Abstract: In this paper, the problem of site characterization is treated as a task of function approximation of the large existing data from standard penetration tests (SPTs) in three-dimensional subsurface of Bangalore, India. More than 2,700 field SPT values (N) has been collected from 766 boreholes spread over an area of 220 -km2 area in Bangalore, India. To get N corrected value ( Nc ) , N values have been corrected for different parameters such as overburden stress, size of borehole, type of sampler, length of connected rod. In three-dimensional analysis, the function Nc = Nc ( X,Y,Z ) , where X , Y , and Z are the coordinates of a point corresponds to Nc value, is to be approximated with which Nc value at any half-space point in Bangalore, India can be determined. An attempt has been made to develop artificial neural network (ANN) model using multilayer perceptrons that are trained with Levenberg-Marquardt back-propagation algorithm. Also, a geostatistical model based on ordinary kriging technique has been ad...

Micromechanical Aspects of Liquefaction-Induced Lateral Spreading

Abstract: This paper reports the results of model-based simulations of 1-g shake table tests of level and sloping saturated granular soils subject to seismic excitations. The simulations utilize a transient fully coupled continuum-fluid discrete-particle model of water-saturated soils. The fluid (water) phase is idealized at a mesoscale using an averaged form of Navier-Stokes equations. The solid particles are modeled at the microscale as an assemblage of discrete spheres using the discrete element method (DEM). The interphase momentum transfer is accounted for using an established relationship. The employed model reproduced a number of response patterns observed in the 1-g experiments. In addition, the simulation results provided valuable information on the mechanics of liquefaction initiation and subsequent occurrence of lateral spreading in sloping ground. Specifically, the simulations captured sliding block failure instances at different depth locations. The DEM simulation also quantified the impact of void redistribution during shaking on the developed water pressure and lateral spreading. Near the surface, the particles dilated and produced an increase in volume, while the particles at deeper depth locations experienced a decrease in volume during shaking.

Implementation of a Critical State Two-Surface Model to Evaluate the Response of Geosynthetic Reinforced Pavements

Abstract: A finite-element model was developed using ABAQUS software package to investigate the effect of placing geosynthetic reinforcement within the base course layer on the response of a flexible pavement structure. A critical state two-surface constitutive model was first modified to represent the behavior of base course materials under the unsaturated field conditions. The modified model was then implemented into ABAQUS through a user defined subroutine, UMAT. The implemented model was validated using the results of laboratory triaxial tests. Finite-element analyses were then conducted on different unreinforced and geosynthetic reinforced flexible pavement sections. The results of this study demonstrated the ability of the modified critical state two-surface constitutive model to predict, with good accuracy, the response of the considered base course material at its optimum field conditions when subjected to cyclic as well as static loads. The results of the finite-element analyses showed that the geosyntheti...

Seismic Rotational Stability of Waterfront Retaining Wall Using Pseudodynamic Method

Abstract: Design of waterfront retaining walls under seismic conditions is an important topic of research among the geotechnical engineering fraternity, and recently there have been studies in which the stability of rigid waterfront retaining walls has been assessed. However, an important aspect of seismic rotational stability of such walls is still missing from the literature archives. The present study shows the importance of rotational displacements for the design of the rigid waterfront retaining wall. Consideration has been made for the calculation of the hydrodynamic pressure as well as the seismic forces, both due to the seismic pressure and seismic wall inertia. These seismic forces have been calculated using the pseudodynamic approach. The free water condition has been considered in the analysis, and thus the hydrodynamic pressure has been considered to exist on the downstream face of the retaining wall as well, and a well-known expression approximating the effect of the inertia of the water due to the earthquake has been used for the estimation of this hydrodynamic pressure force. Simple expressions for the calculation of rotational displacement both during and after the earthquake have been proposed, and typical results have been obtained. It is observed that with an increase in the ratio of the water level to the total height of the wall from 0.50 to 1.00 the rotational displacement of the wall increases by about 110%. Similar trend of an increase in the value of the rotational displacement was observed for an increase in the values of the horizontal and vertical seismic acceleration coefficients. Also, the parametric study carried out in the analysis suggested that the rotational displacement is sensitive to other parameters such as the upstream water height, pore pressure ratio, soil, and wall friction angles. Due to nonavailability of the results in which rotational stability of the waterfront retaining wall under the seismic conditions has been studied, the results from the present analysis seem to bring out a unique approach.

Analysis of Soil Strength Degradation during Episodes of Cyclic Loading, Illustrated by the T-Bar Penetration Test

Abstract: Pipelines and risers form an essential part of the infrastructure associated with offshore oil and gas facilities. During installation and operation, these structures are subjected to repetitive motions which can cause the surrounding seabed soil to be remolded and soften. This disturbance leads to significant changes in the operative shear strength, which must be assessed in design. This paper presents an analytical framework that aims to quantify the degradation in undrained shear strength as a result of gross disturbance—in this case through repeated vertical movement of a cylindrical object embedded in undrained soil. The parameters of the framework were calibrated using data obtained in a geotechnical centrifuge test. In this test a T-bar penetrometer, which is a cylindrical tool used to characterize the strength of soft soil, was cycled vertically in soil with strength characteristics typical of a deep water seabed. Using simple assumptions regarding the spatial distribution of “damage” resulting fr...

Simple yield surface expressions appropriate for soil plasticity.

Abstract: The objective of this paper is to present a number of simple, practical, and useful analytical expressions of a yield surface for geomaterials. In classical plasticity, the analytical expression of a yield surface defines the locus of points in stress space at which plastic flow initiates, and the corresponding function must depend on direct and mixed invariants of stress and tensor-valued internal variables. One single function describes a yield surface in order to avoid singularities and computational difficulties arising from the use of multiple functions representing intersecting surfaces in stress space that are often used for cap-type models in soil plasticity. The presented functions are conveniently subdivided in three main categories depending on the type of analytical expression used, and they all describe properly closed yield surfaces which are continuous and convex. The internal variables in these functions can be used in order to address classical plasticity features such as isotropic and ki...

Implementation and Application of a New Elastoplastic Model Based on a Multiaxial Criterion to Assess the Stress State near Underground Openings

Abstract: The inelastic MSDPu (for Mises-Schleicher and Drucker-Prager unified) criterion has been developed over the last decade, and has been applied to simple problems for a wide range of geomaterials. This paper presents the approach taken to introduce this multiaxial criterion into a commercially available finite difference code using an elastoplastic framework. The paper begins with a brief review of the MSDPu formulation. Then, the main components of the elastoplastic model and the implementation procedure are described. The ensuing model, called MSDPu -EP (for MSDPu elastoplasticity model), is then validated against some existing and recently developed analytical solutions for the stress state around a circular opening. The newly developed model is further applied to evaluate the stress state near underground openings, using the geometry of a tunnel and of vertical backfilled stopes. A brief discussion follows.

On a Possible Role of Rayleigh Surface Waves in Dynamic Slope Failures

Abstract: This contribution addresses the effect of a surface wave on the dynamic behavior of a slope. In particular, the interaction of a Rayleigh surface wave, possibly generated by an earthquake or nearby blasting, with a simple wedge-shaped slope is considered. A two-dimensional elastodynamic analysis suggests that the amplitudes and phase shifts of the surface waves reflected and transmitted at the crest strongly depends on the inclination of the slope face, and the superimposition of the reflected and incident waves may induce large stress amplification and thus produce open cracks in the top surface of the slope. The computational semianalytical results are used to investigate the generation mechanism of slope failure caused in the city of Sendai dynamically by the 1978 Miyagi-ken-oki, Japan, earthquake. Finally, the significance of the effect of Rayleigh wave propagation on dynamic slope stability is discussed in comparison with the influence of body waves.

Modeling Permanent Deformation of Unbound Granular Materials under Repeated Loads

Abstract: 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.

Anisotropy in the Spatial Distribution of Roller-Measured Soil Stiffness

Abstract: The geostatistical analysis of roller-measured soil properties (from continuous compaction control and intelligent compaction) is required for advanced quality control/quality assurance of earthwork and asphalt compaction. This paper explores the existence of anisotropy in the spatial distribution of roller-measured soil stiffness and the effect of anisotropy on kriging. Field testing was conducted to collect roller measurement value (MV) data over typical roadway embankment evaluation areas and on a large square area to enable a robust investigation of anisotropy. The semivariogram analysis of the field data clearly indicates that range anisotropy exists. The spatial distributions of roller MV data are different in the longitudinal x -direction than in the transverse y -direction. Magnitudes of range anisotropy ( x-range/y-range ) varied from 2.4 to over 5. The observed range anisotropy is not due to the roller measurement system; rather, it is likely due to the directional nature of earthwork constructi...

Algorithm to Generate a Discrete Element Specimen with Predefined Properties

Abstract: The discrete element method is a powerful numerical tool in simulating the behavior of granular materials. It bridges the gap between continuum mechanics and physical modeling investigations. In spite of the significant achievements to date, some major problems are yet to be solved including the development of realistic large-scale models with initial conditions similar to those encountered in real problems. This paper introduces a computational method to generate a large-scale packing with predefined porosity and grain-size distribution in three-dimensional space based on a small initial sample packing. The developed method is implemented into an open- source computer code and used to generate specimens with known properties. The results showed that, under static condition, specimens generated using the proposed algorithm exhibited realistic behavior suitable for geotechnical applications. In addition, the controlled structure of the initial sample packing is successfully transferred to the final packing. DOI: 10.1061/ASCEGM.1943-5622.0000028 CE Database subject headings: Discrete elements; Geotechnical engineering; Grain size; Porosity; Algorithms; Granular materials. Author keywords: Discrete element method; Geotechnical engineering; Packing; Grain-size distribution; Porosity; Dynamic packing.

Experimental Results Analysis for UiTM BWB B aseline!I and Baseline!II UAV Running at 0.1 Mach number

Abstract: This paper presents results analysis for two models of UiTM Blended Wing Body (BWB) UAV tested in UiTM Low Speed Wind Tunnel. The first model is known as the BWB Baseline!I and the new model known as BWB Baseline!II. The Baseline!II has a simpler planform, broader!chord wing and slimmer body compared to its predecessor while maintaining wingspan. The wind!tunnel experiments were executed at around 0.1 Mach number or about 35m/s with 1/6 scaled down model. Baseline!I is designed with centre elevator while Baseline!II uses canard for pitching motion purpose. The experiments were carried out at various elevator and canard deflection angles. The lift coefficient, drag coefficient, pitching moment coefficient, L/D ratio and drag polar curves were plotted to show the performance of aircraft at various angle of attack. For zero elevator and canard deflection the results show similar trends in terms of lift curve, drag curve and pitching moment curves for both aircrafts.

Consolidation Behavior of Soils Subjected to Asymmetric Initial Excess Pore Pressure Distributions

Abstract: Although the consolidation settlements beneath foundations and embankments are rarely one dimensional, Terzaghi's one-dimensional consolidation theory is often applied to these situations to approximate consolidation behavior. This paper investigates the consolidation behavior of a soil stratum subjected to various initial excess pore pressure distributions which occur under one-dimensional loading. The results show that analysis in terms of average degree of consolidation provides an incomplete representation of the consolidation behavior. While the average degree of consolidation curves for all uniform and linearly varying initial distributions are identical, the degree of consolidation isochrones for each distribution are unique. Furthermore, the application of a bottom-skewed initial excess pore pressure distribution results in a redistribution of pore pressures toward the skewed region so that an increase in excess pore pressure occurs at some depth after consolidation has already commenced. As a result, conventional consolidation relationships are considered inappropriate for these cases, and an alternative method of consolidation analysis in terms of normalized pore pressures is proposed.

Nonlinear Analysis of Torsionally Loaded Piles in a Two-Layer Soil Profile

Abstract: This paper presents a method for predicting the nonlinear response of torsionally loaded piles in a two-layer soil profile, such as a clay or sand layer underlain by rock The shear modulus of the upper soil is assumed to vary linearly with depth and the shear modulus of the lower soil is assumed to vary linearly with depth and then stay constant below the pile tip The method uses the variational principle to derive the governing differential equations of a pile in a two-layer continuum and the elastic response of the pile is then determined by solving the derived differential equations To consider the effect of soil yielding on the behavior of piles, the soil is assumed to behave linearly elastically at small strain levels and yield when the shear stress on the pile-soil interface exceeds the corresponding maximum shear resistance To determine the maximum pile-soil interface shear resistance, methods that are available in the literature can be used The proposed method is verified by comparing its res

Monitoring and Modeling Grout Efficiency of Lifting Structure in Soft Clay

Abstract: 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 o...

Dynamic Numerical Analysis of Antimoisture-Damage Mechanism of Permeable Pavement Base

Abstract: 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 o