Development Of Pore Water Pressure Research Articles

Equivalent seismic behaviors of artificial frozen-thawed soft clay with a new reduction factor of shear stress

The artificial ground freezing (AGF) technique is widely used in the construction of underground structures, and the deformation of soft clay is more significant after freezing-thawing cycles. Moreover, many earthquake disasters indicate that the engineering in soft soil areas experience huge risks to seismic fortification. In this paper, the inversion formula of seismic acceleration time history for different peak ground accelerations (PGAs) in the frequency domain was derived. The maximum peak acceleration and maximum dynamic shear stress in the undisturbed and frozen-thawed soft clay sites were analyzed by DEEPSOIL. The reduction factor of dynamic shear stress suitable for the clay field was calculated to provide basic parameters for the cyclic triaxial tests considering different confining pressures, dynamic stress amplitudes and loading frequencies. The ground motion acceleration of soft clay sites has an amplification effect, and that of frozen-thawed soft clay sites is more obvious. The reduction factor of shear stress for the clay site is overestimated by the liquefaction resistance shear stress method. The axial strain of the frozen-thawed clay reaching failure is less than that of the undisturbed clay. Under the same seismic shear stress, the development of the excess pore water pressure in frozen-thawed clay is more significant than that in undisturbed clay.

A bounding surface model for gassy clay

Gassy clay can be frequently encountered in the seabed. Gassy clay is a composite material with a saturated soil matrix and discrete gas bubbles. The soil behaviour is significantly affected by the interaction between the soil matrix and gas bubbles. Existing constitutive models have all focused on the response of normally consolidated clay. These models cannot give reasonable prediction of pore water pressure evolution for overconsolidated clay in shear. This can cause poor prediction of overconsolidated gassy clay behaviour because pore water pressure has a significant influence on soil-gas interaction. A new bounding surface model for gassy clay is proposed to model the elastoplastic behaviour of this soil. The gas cavities are assumed to have a detrimental effect on the plastic modulus and shear strength as they affect the integrity of the soil structure. Bubble flooding can occur within the soil, which makes the saturated soil matrix partially drained under a globally undrained condition, leading to higher stiffness and shear strength of gassy clay. The model has been validated by the undrained triaxial compression tests on gassy Malaysian Kaolin and Speciwhite Kaolin clay. Effect of the total stress path on undrained gassy clay behaviour has been analysed.

Study on the dynamic pore water pressure model of centerline tailings sand based on dynamic triaxial tests

The increase of pore water pressure under a dynamic load is an important reason for the vibration liquefaction of saturated sand. Therefore, studying the dynamic pore water pressure model of tailings sand plays an important role in the seismic liquefaction analysis of tailings ponds. In this paper, the dynamic pore water pressure development characteristics of tailings fine sand and tailings silt in a tailings pond with the centerline method are studied by dynamic triaxial tests. The research results show that the liquefaction dynamic pore pressure ratio of tailings fine sand shows a trend of "rising–smooth–rising" with increasing vibration frequency ratio, and the liquefaction dynamic pore-pressure ratio of tailings silt shows an approximate linear and stable increasing trend. According to the development law of dynamic pore pressure, a new tailings sand pore pressure stress model is proposed in this paper, and the fitting effect is compared with four different pore pressure models, which verifies the applicability of the new model to predict the growth of dynamic pore pressure in tailings and silt.

Energy-based approach to study liquefaction triggering in homogeneous and stratified soils under consolidated undrained cyclic loading

Pore water pressure development through seismic effect is one of the key reasons for liquefaction failures in the foundations, dams, bridges, slopes and other vulnerable geotechnical engineering structures. The energy dissipation theories have provided a remarkable understanding of the pore water pressure generation inside a soil skeleton. In the present study, a series of consolidated undrained cyclic triaxial tests have been performed to evaluate the normalized dissipated energy (Wn) required for triggering liquefaction in both homogeneous and stratified soil specimens (prepared using silt interlayer) to replicate the site conditions nearby marine or alluvial deposits. The generated hysteresis loops using cyclic loading facilitate the calculation of dissipated energy. Also, the test results indicated a significant variation in the dissipated energy of homogeneous specimens at different magnitudes of cyclic stress ratios (CSR) and relative densities (Dr). With an increase in the cyclic stress ratio from 0.14 to 0.20, the trend of dissipated energy was observed to be different when relative densitie of sand varied from 30% to 65%. In the stratified specimens, thickness (t) and location of the silt layer (d) in the given soil specimen were the major influencing factors for estimating the liquefaction potential in loose conditions. Additionally, the highest value of Wn,max was obtained as 0.51 for the stratified specimen with topt = 28 mm at a cyclic stress ratio of 0.14. Based on the trendline variations, empirical models have been developed to estimate the normalized dissipated energy (Wn) for both homogeneous and stratified conditions. The developed models for homogeneous specimens are functions of CSR and Dr, whereas, in the case of stratified specimens, t, d and σd/σ'c (σd = deviator stress, σ'c = effective confining stress) have been utilized to predict the Wn with an satisfactory R2 value above 0.90. From the analysis of liquefaction resistance curves, the energy-based approach used in this study has been observed to provide more realistic results than the pore pressure ratio and strain-based failure criteria.

Finite element analysis on dynamic behavior of sheet pile quay wall dredged and improved seaside subsoil using cement deep mixing

Sheet pile wall structures are commonly applied in coastal projects, particularly for the quay wall. This structural type normally is used in places where the ground has a low bearing capacity and is easily penetrable. Many sheet pile quay walls constructed in the past had low front water depth and did not satisfy the requirements of current standards. This issue could be addressed by improving the ground in front of the wall using cement deep mixing (CDM) and then excavating to increase the water depth in front of the wall. This paper numerically evaluated the dynamic behavior of the sheet pile wall after renovation. The numerical model was performed based on the finite element method (FEM) using the PLAXIS 2D program. The study focused on investigating typical parameters of the quay wall improved using the CDM, such as bending moment and displacement of sheet pile and the development of excess pore water pressure (EPWP) in the backfill. These results were compared to those of the quay wall without the CDM to elucidate the advantages of this method. In addition, the influence of some factors on the quay wall behavior, such as earthquake excitation characteristics, CDM area, and CDM strength, was also evaluated. The results demonstrated that the ground improvement using the CDM significantly decreased the bending moment and displacement of the sheet pile wall. The excitation characteristics did not affect the deformed shape of the sheet pile. With the constant CDM depth, the sheet pile displacement decreased with an increase in the improvement width until it reached a limitation. The increasing CDM strength also decreased the displacement of the wall until it raised a certain value. This demonstrated that this method was technically feasible, and it could be considered to study further by experiment before applying in practice.

Centrifuge model studies on the performance of earthen dams with geocomposite internal drain subjected to pseudostatic seismic loading

This paper evaluates geocomposite (GC) as an internal drain for seepage control in earthen dams subjected to upstream impoundment and inertial loading through centrifuge model tests. A total of five centrifuge tests were performed on a homogeneously built small earthen dam section having prototype height of 7.2 m with 1H:1V side slopes at 30 g-level using a 4.5 m radius large beam geotechnical centrifuge available at the Indian Institute of Technology Bombay, India. The studied earthen dam models had an internal drain in the form of (a) a geocomposite horizontal drain (GC HD); (b) a sand-sandwiched geocomposite horizontal drain (SSGC HD); (c) a geocomposite chimney drain (GC CD); and (d) a sand-sandwiched geocomposite chimney drain (SSGC CD). The seepage-deformation response of the GC equipped earthen dam models is presented in terms of the development of pore-water pressure (PWP), phreatic surfaces, surface settlements (sc), and downstream slope face movements (sf). The behavior of the earthen dam model without any internal drain is also presented for comparison. In the case of an earthen dam with GC internal drain both as HD and CD, it was found to be efficient up to some extent in restricting phreatic surfaces, but phreatic surfaces were observed to be close to downstream side slope. However, a sand-sandwiched GC internal drain HD and CD seemed more promising in restricting the phreatic surface much within the downstream region and imparting higher stability even during sustained inertial loading conditions. The study concludes that SSGC chimney drain can be safely adopted for seepage control in small earthen dams and similar geotechnical structures viz levees, raw water reservoirs (RWRs), coastal protection structures, etc.

8th Ishihara lecture: Holistic evaluation of liquefaction response

Soil liquefaction during earthquakes is a highly dynamic process involving rapid development of excess pore water pressures (EPWP), reduction in soil stiffness and strength, and diffusion of EPWPs through water flow. In addition, the liquefaction response is characterized by strong cross-layer interactions that significantly influence the severity of liquefaction and overall system response of liquefying deposits. To emphasize the importance of dynamic interactions and provide an in-depth understanding of the liquefaction response, a framework for a holistic evaluation of the liquefaction response is presented. Three key aspects of the response are required to be concurrently considered in the holistic evaluation of the liquefaction response: element (soil) response, cross-layer interactions (system response) and intensity of the input motion. The proposed approach is applied to a comprehensive series of nonlinear dynamic analyses (NDAs) of well-documented case history sites from Christchurch, New Zealand, to identify key interaction mechanisms and quantify effects of dynamic interactions on the liquefaction response. As state-of-practice simplified liquefaction evaluation procedures ignore interactions within the deposit, results from simplified analyses substantially differ from those observed in NDA and show significant anomalies in the evolution of the liquefaction response throughout the depth of liquefiable deposits. A systematic approach for an NDA-based improvement of simplified analysis is proposed to incorporate interaction mechanisms and system response effects in simplified liquefaction evaluation procedures.

Experimental simulation for moisture damage of saturated asphalt mixture and evolution of mixture’s pore water pressure, accumulative strain

Moisture damage has significant impact on pavement’s performance and service life, researching this kind of distress’ mechanical mechanism, experimental simulation protocol or theoretical analysis method continues to be the research that should be conducted in depth for pavement researchers. But, due to the complexity of this distress’ influencing factors, there is still not a satisfactory research result by far, particularly for its experimental simulation test, the current research lack of a satisfactory apparatus or protocol that can simulate asphalt mixture’s moisture damage in lab. So then, this paper, basing on a fully mechanical analysis in advance for asphalt pavement’s moisture damage, develops an experimental apparatus being capability to simulate and investigate asphalt mixture’s moisture damage in lab by improving a dynamic triaxial tester, then utilizes this improved triaxial tester investigate moisture damage of asphalt mixture with different air void percent or applied by different confining pressure, and acquires these mixture’s characteristics regarding their pore water pressure evolution, strain cumulation, specimen deformation as well as their influencing factors, then classifies these test results into three types according to their characteristics. The test results demonstrate, this developed apparatus can comparatively satisfactorily simulate mixture’s moisture damage phenomena in lab, its simulation test results are close to field investigation results, and air void percent, confining pressure and loading frequency are the principal factors that have significant impact on mixture’s moisture damage test results. For the specimen with lower air void percent or under a higher confining pressure, their test results are primarily type 1, whose pore water pressure and cumulative strain are relatively low, deformation are pure compression. Whereas, for the specimen with larger air void percent or applied by higher confining pressure, their pore water pressure and cumulative strain are usually larger, specimen are generally observed with stripping or cracking in the end of test, even some are found with diagonal cracks, these characteristics are classified as type 3. As for type 2, their test results are primarily between that of type 1 and type 3, their pore water pressure, cumulative strain are relatively large, yet specimen’s deformation mainly attribute to compression, and only swelling in radial direction or slight stripping are found with specimens.

Microscopic analysis of the influence of soil properties on the suction bucket installation in sand based on the CFD-DEM model

This paper presents a numerical simulation for exploring the characteristics of soils and porewater pressure development during the suction bucket installation in the sand. The dynamic-mesh technology and new drag force model considering irregular particle shapes are adopted in the CFD-DEM model. By comparing the results of experimental and theoretical models, the validation of the numerical program has been proved. Then, this study is motivated by the fact that marine sediments generally exhibit a porosity decreasing with depth because of consolidation under gravity. Results demonstrate that the seabed face porosity is the critical factor that causes differences in penetration resistance and porewater pressure distribution at late installation stages. Additionally, penetration mechanisms with different depths are analyzed by particle migration, porewater pressure distribution, and flow field. Based on microscopic analysis, apart from seepage would induce a noticeable migration of fine particles, the apparent soil-squeezing effect is another essential factor to cause soil displacement and expansion in dense sand. Finally, the bucket can be safely installed in sand, despite the permeability coefficient inside the bucket reaching the critical state. Such a macro and micro insight will further facilitate the design of suction bucket installation, particularly considering the influence of sand permeability.

Excess pore water pressure behavior of saturated soft clay under cyclic confining pressure with different frequencies

The excess pore water pressure is main factor affecting the dynamic response of saturated soft clay under traffic loads. Recognize that, cyclic triaxial tests with and without cyclic confining pressure were carried out to study the development of excess pore water pressure of saturated soft clay. The impacts of factors, such as cyclic stress ratio (CSR), loading frequency, and cyclic confining pressure, were analyzed. Excess pore water pressure increases with increasing cyclic stress ratios, while decreases with increasing loading frequencies. Nevertheless, with increasing cyclic confining pressures, the maximum excess pore water pressure increases, while the minimum excess pore water pressure remains unchanged. Besides that, the greater CSR and cyclic confining pressure deliver an increment of both maximum and minimum excess pore water pressure rate. However, the excess pore water pressure rate - time curves coincide under different loading frequencies. Meanwhile, both the normalized maximum and minimum excess pore water pressure rates are linearly proportional with time under different test conditions in logarithmic coordinates. Based on that, both maximum and minimum excess pore water pressure prediction models, relating to the above factors, are proposed, and the predicted results accord well with the measured data.

Development and Influence of Pore Pressure around a Bucket Foundation in Silty Soil

Silty soil is common in the seabed of eastern coastal areas of China. The behaviors of the silty soil and a bucket foundation installed within it need more study. In this work, model tests of a bucket foundation in silty soil were performed. The development of the excess pore water pressures in the different positions around the bucket was measured. Different loading conditions, with a change in the horizontal cyclic load amplitude ratio, horizontal cyclic frequency, and vertical load ratio, were considered. The effects of the pore water pressure on the shear strength of the soil around the bucket and the horizontal bearing capacity of the bucket foundation were investigated. The results show that the normalized pore water pressures close to the bucket wall at depths between 0.1 L and 0.3 L exhibit distinct change under the cyclic load. Consistent with the distribution of the pore water pressure, the degradation of the undrained shear strength is more obvious with a greater load amplitude ratio, a greater load frequency, and a smaller vertical load. The degradation rate of the static horizontal ultimate bearing capacity is in a range of 1.57% to 14.90%, under different loading conditions.

Thermo-hydro-mechanical behavior of energy foundations in saturated glacial tills

This study focuses on the effect of temperature- and –stress dependent hydraulic conductivities on the thermo-hydro-mechanical behavior of energy foundations installed in saturated glacial tills. A thermo-poroelastic model based on finite element method was developed and validated against field measurements from a case study in the literature, then was used to simulate four different energy foundations installed on the Urbana-Champaign campus of University of Illinois. Coupled thermo-hydro-mechanical properties were integrated into the numerical analyses based on laboratory characterization of the hydraulic conductivities of several soil samples at different temperatures and confining stresses. The results indicate that the transient evolution of pore water pressure, axial stress, and shaft resistance are significantly influenced by temperature- and stress- dependent hydraulic conductivity. Changes in axial stress and shaft resistance peak at early times when excess pore water pressures are highest. Long-term changes in axial stress and shaft resistance were less than the short-term peak values, highlighting the importance of considering the evolution of coupled soil properties to capture the peak response. This study demonstrates that consideration of coupled material properties is required to capture the coupled response of energy foundations in saturated glacial tills.

Effects of initial static shear stress on cyclic behaviour of sand stabilised with colloidal silica

Colloidal silica (CS) grouting is a soil improvement technique introduced as an innovative remedial measure against seismic liquefaction. It consists of injecting soils with a time-hardening, nanosilica-based solution forming a silica gel among soil particles. This paper presents the results of an experimental study on the effects of an initial static shear stress on the behaviour of a cyclically loaded clean sand stabilised with 5% CS. Undrained cyclic triaxial tests were performed to analyse the cyclic response of loose untreated and stabilised sand specimens, isotropically or anisotropically consolidated at the same initial mean effective stress. The consolidation stage was used to provide insight on the compressibility of stabilised soil. Stress–strain behaviour, pore water pressure response and cyclic shear resistance were investigated. The results showed that: (i) stabilised sand exhibits higher compressibility than the untreated one during isotropic consolidation; (ii) cyclic strength is higher for stabilised sand than for the untreated one, increasing as the degree of anisotropic initial stress increases; and (iii) extra pore water pressure development does not depend on the degree of initial anisotropy for stabilised sand, while the same does not hold for untreated sand. Simplified relationships are proposed to describe the consolidation process and the residual extra pore water pressure build-up process.

Effects of axial loading on dynamic response of laterally loaded single piles in liquefiable layered soil of Kolkata city considering nonlinearity of soil

In the present study, an advanced nonlinear finite-element based 3D numerical study has been carried out to investigate the effects of axial loading on dynamic response of soil-pile system in liquefiable layered soil deposits of Kolkata city. An advanced soil constitutive law based on multi-yield surface plasticity model implemented in fully-coupled u-p formulation is adopted for soil-fluid interaction and pore water pressure development reasonably. The present model is validated with the past experimental results. Then, a detailed systematic parametric study is performed for numerical simulation of pile failures in layered soil deposit under axial loading by taking into account various soil conditions, pile and ground motion parameters. It is seen that the depth of liquefaction (DL) is decreased from 11.5 to 1.5 m adjacent to the pile when the axial load on pile increases from 0 to 1327 kN. Parametric studies also reveal that the bending moment response of pile under axial loading can be higher in non-liquefiable condition, with reference to the liquefiable condition. The peak lateral displacement decreases by 83.2% in non-liquefiable condition and 60.71% in liquefiable condition due to decrease of axial load from 1327 to 0 kN. Also, peak bending moment developed in the pile decreases by 97.2% in non-liquefiable condition and 82.7% in liquefiable condition when the axial load reduces from 1327 to 0 kN. So, the designer should be considered both extreme scenarios for safe and economical design. Also, it is noticed that the buckling capacity of pile is improved significantly by using larger diameter pile and the bending capacity is increased by selecting higher grade of concrete. It is concluded that the bending and buckling failure mode may be avoided by selecting a suitable combination of material strength and pile geometry.

Study on Reinforcement Mechanism and Reinforcement Effect of Saturated Soil with a Weak Layer by DC

This paper presents a numerical investigation on the improvement mechanism of dynamic compaction (DC) in saturated soil of a weak layer with high levels of groundwater, using an improved fluid–solid coupling method with a Drucker–Prager–Cap soil model. The numerical model is verified by comparing with published test data at first, which show that the dual-phase coupling method can approximately reflect the development law of excess pore water pressure and the improvement effect of layered saturated soil foundation under DC. Then, based on the numerical model, the influences of the thickness and depth of the weak layer as well as tamping energy on the development and dissipation of excess pore water pressure, effective stress, and the relative degree of reinforcement during DC were investigated. The results showed that the embedment depth and thickness of the weak interlayer may greatly affect the effective reinforcement depth of DC. Meanwhile, the tamping energy and the groundwater table also play a great role in the improvement of the layered saturated soil under DC. The groundwater table should be lowered by dewatering or adding a drainage layer to achieve a better compaction effect during DC.

Two-Phase Two-Layer Depth-Integrated SPH-FD Model: Application to Lahars and Debris Flows

The complex nature of debris flows suggests that the pore-water pressure evolution and dewatering of a flowing mass caused by the high permeability of soil or terrain could play an essential role in the dynamics behavior of fast landslides. Dewatering causes desaturation, reducing the pore-water pressure and improving the shear strength of liquefied soils. A new approach to landslide propagation modeling considering the dewatering of a mass debris flow has drawn research attention. The problem is characterized by a transition from saturated to unsaturated soil. This paper aims to address this scientific gap. A depth-integrated model was developed to analyze the dewatering of landslides, in which, desaturation plays an important role in the dynamics behavior of the propagation. This study adopted an SPH numerical method to model landslide propagation consisting of pore-water and a soil skeleton in fully or partially saturated soils. In a two-phase model, the soil–water mixture was discretized and represented by two sets of SPH nodes carrying all field variables, such as velocity, displacement, and basal pore-water pressure. The pore-water was described by an additional set of balance equations to take into account its velocity. In the developed two-layer model, an upper desaturated layer and a lower saturated layer were considered to enhance the description of dewatering. This is the so-called two-phase two-layer formulation, which is capable of simulating the entire process of landslides propagation, including the large deformation of soils and corresponding pore-water pressure evolutions, where the effect of the dewatering in saturated soils is also taken into account. A dam-break problem was analyzed through the new and previously developed model. A flume test performed at Trondheim was also used to validate the proposed model by comparing the numerical results with measurements obtained from the experiment. Finally, the model was applied to simulate a real case lahar, which is an appropriate benchmark case used to examine the applicability of the developed model. The simulation results demonstrated that taking into account the effects of dewatering and the vital parameter of relative height is essential for the landslide propagation modeling of a desaturated flowing mass.

Load history idealisation effects for design of monopiles in clay

Evaluation of the characteristic behaviour of clay under cyclic loading is desirable and essential for an optimised monopile design of offshore wind turbines (OWTs). In current design practice, an irregular storm history is transformed into an idealised regular cyclic history with loading packages of uniform amplitude in ascending order. This paper investigates the effects of load representations by performing a series of load-controlled cyclic triaxial tests. The load histories investigated consist of a calculated 1 h storm loading on an OWT monopile foundation in the North Sea and its representations with different orders of the idealised load packages. The role of the average shear stress is discussed by comparing the shear strain evolution, pore water pressure accumulation, soil stiffness and strength. Cyclic degradation obtained with and without average shear stress components is studied. The experimental investigations in this paper indicate that the current design practice of load idealisation may not necessarily be conservative. The average shear stress affects the strain accumulation significantly but has relatively minor effects on the evolution of pore water pressure. It is suggested that the soil element response subjected to irregular load history should be investigated further from both experimental and numerical perspectives to develop an improved procedure for monopile design.

An experimental investigation into the evolving instability of a subaqueous mild silty slope under progressive waves

The silty sediments that are widely distributed in estuaries and deltas are susceptible to slope instability due to ocean storms. Flume experiments were carried out in this study to investigate the characteristics and failure process of a subaqueous mild silty slope subjected to ocean waves. The results show that the wave steepness varies accordingly to wave propagation over the mild silty slope due to shoaling effect. Where the wave steepness is up to the threshold value of 0.04, liquefaction may occur in silty slopes due to the substantial amount of residual pore water pressure development. In this process, the maximum wave pressure appears near the wave breaking point where it may be increased by about 40% compared with that at bottom of the slope; this means that liquefaction may primarily first occur in regions near the wave breaking point and become the predominant trigger for the overall slope instability. The maximum liquefaction and sliding depth of silty seabed may reach 0.1–0.15 times the wavelength for wave steepness of 0.04–0.10. Unlike the failures of a loose sandy slope that are characterized by a slumping stage along with a sudden rise in pore water pressure, wave induced failure of the mild silty slope progresses in three distinct stages, i.e., (i) initial erosion and scouring, (ii) coupled development of liquefaction and scour, and (iii) oscillating and sliding of sediments.

Three-dimensional fully coupled hydro-mechanical-chemical model for solute transport under mechanical and osmotic loading conditions

Mechanical deformation and chemico-osmotic consolidation of clay liners can change its intrinsic transport properties in all direction and can alter fluid and solute transport processes in the entire model domain. These phenomena are described inadequately by lower-dimensional models. Based on the Biot’s consolidation theory, fluid and solute mass conservation equations, a three-dimensional (3D) fully-coupled hydro-mechanical-chemical (HMC) model has been proposed in this study. The impacts of mechanical consolidation and chemico-osmotic consolidation on permeability, hydrodynamic dispersion, solute sorption, membrane efficiency, and chemical osmosis are considered in the model. The model is applied to evaluate performances of a single compacted clay liner (CCL) and a damaged geomembrane-compacted clay composite liner (GMB/CCL) to contain a generic landfill contaminant. Effect of model dimensionality on solute spread for CCL is found to be marginal, but for GMB/CCL the effect is significantly large. After 50-year simulation period, solute concentration at the half-length of the GMB/CCL liner is predicted to be 40% of the source concentration during 1D simulation, which is only 6% during the 3D simulation. The results revealed approximately 74% over-estimation of liner settlement in 1D simulation than that of the 3D for GMB/CL system. Solute spread accelerates (over-estimates) vertically than horizontally since overburden load and consequent mechanical loading-induced solute convection occurs in the same direction. However, in homogeneous and isotropic soils, horizontal spread retards the overall migration of contaminants, and it highlights the importance of 3D models to study solute transports under mechanical and chemico-osmotic loading conditions in semi-permeable clays, especially, for damaged geomembrane-clay liners. The results show the utility of geomembranes to reduce soil settlement, undulation, and restriction of solute migration. Furthermore, application of geomembrane can inhibit development of elevated negative excess pore water pressure at deeper portion of a clay liner.

Influence of root distribution patterns on soil dynamic characteristics

Slopes along the highway and railway routes are subjected to not only static loads but also dynamic loads generated by vehicles and trains. The induced excessive deformation potentially poses a threat to slope stability. In terms of the extensive application of ecological slope protection, plants play a critical role in slope stability, as the roots can enhance the shear strength of the soil. This study aims to investigate the influence of different root distribution patterns on the dynamic characteristics induced by cyclic loading. By conducting a group of dynamic triaxial tests, the results indicate that the root system can significantly enhance the liquefaction resistance of the soil when the soil is subjected to lower dynamic loads, and the cross arrangement has a better-reinforced effect than the mixed arrangement. The reinforced effect was not obvious when the soil was subjected to a dynamic load with a larger stress amplitude. In addition, based on the validation of the seed model, a new pore water pressure development model was proposed according to the test results. Overall, the research provides a new model and some innovative observations to better understand the dynamic behavior of root-reinforced soil.