Chao Xu

• Professor at Tongji University

Nonwoven geotextiles are commonly utilized as filter materials in drainage and filtration engineering. This study focuses on the clogging phenomenon of the nonwoven geotextile filter wrapping the blind drain in the active anti-floating technology of underground structures. In this paper, the filtration compatibility of clay-nonwoven geotextiles was...

The tensile strength of geogrids and the shear strength of the reinforced soil interface are critical technical indicators for designing reinforced soil structures. This study developed a temperature-controlled apparatus to examine the tensile properties of geogrids subjected to freeze-thaw cycles within the soil, and the effect of interface temper...

Geosynthetics reinforced soil (GRS) abutment has been widely used in the construction of small to medium single-span bridges and shows good service performance in engineering projects. Vertical stress distribution plays an important role for engineering design of the GRS abutments. Three centrifugal model tests of GRS abutments were carried out to...

The purpose of this study is to assess effects of two different simulation methods (i.e., interfaces with a single spring-slider system and interfaces with double spring-slider systems) for interactions between reinforcement and the surrounding medium on the performances of geosynthetic-reinforced soil (GRS) structures when conducting numerical ana...

This study conducted plane-strain scaled model tests to investigate the deformation characteristics of geosynthetic reinforced soil (GRS) abutments subjected to vertical loads. Setback distance, i.e., the distance between the back of the abutment facing and the front of the loading plate, was chosen as the investigated influencing factor since it i...

To avoid serious clogging and loss of drainage capacity, which puts the underground structure at risk of anti-floating failure, the buried drainage filter must be equipped with a nonwoven geotextile layer. In this scenario, nonwoven geotextiles are subjected to normal compressive stress, which can cause changes in geotextile porosity and structure,...

Geotextile filters have gained extensive applications in geotechnical and geoenvironmental drainage systems. Despite of the abundant research about geotextiles filtering coarse-grained soils, there is little experimental study on the performance of geotextiles filtering fine-grained soils. Since clogging and blinding of geotextiles are more likely...

This paper investigated effects of geogrid reinforcement on the load transfer in pile-supported embankment under cyclic loading using self-moving trapdoor tests. In the self-moving trapdoor test setup, the trapdoor between two stationary portions (which were equivalent to the piles) was supported by compression springs to simulate the subsoil. Quar...

Soil arching exists in many earth structures, such as pile-supported embankments, tunnels, buried pipes, and retaining walls. These earth structures are sometimes subjected to surface footing loading. Limited studies showed that surface footing loading weakened active soil arching formed in backfill material; however, this effect has not been well...

In this study, three-dimensional numerical analyses were carried out to investigate the effects of reinforcement pullout resistance including facing connection strength on the behavior of geosynthetic-reinforced soil (GRS) piers under a service load condition. Three different piers were investigated in this study, which simulated different levels o...

Geosynthetic-encased stone column (GESC) has been proven as an effective alternative to reinforcing soft soils. In this paper, a series of centrifuge model tests were conducted to investigate the performance of GESC-supported embankment over soft clay by varying the stiffness of encasement material. The enhancement in the performance of stone colum...

In this paper, an analytical method was proposed to predict the mechanical behavior of embedded planar reinforcements subjected to pullout loads, and a tri-linear shear slip model was employed in the analytical method to consider the residual shear strength at the reinforcement-soil interface. The overall process of the pullout behavior was charact...

Geosynthetics have been widely used in the construction of reinforced soil structures and yet the reinforcing mechanisms of geosynthetics have not been fully understood. Eight biaxial compression model tests of geosynthetic-reinforced soil (GRS) were conducted in this study under a plane strain condition to investigate the reinforcing mechanisms of...

A scaled plane-strain shaking table test was conducted in this study to investigate the seismic performance of a Geosynthetic Reinforced Soil-Integrated Bridge System (GRS-IBS) with a full-length bridge beam resting on two GRS abutments at opposite ends subjected to earthquake motions in the longitudinal direction. This study examined the effects o...

Three centrifuge model tests were conducted to investigate the influence of the number of geosynthetic layers and the pile clear spacing on the global performance of Geosynthetic-Reinforced Pile-Supported (GRPS) embankments with side slopes constructed on soft soil foundations. This study found that the change of the geogrid number from one to two...

Soil arching exists in many geotechnical applications, including tunnels, buried pipes, and geosynthetic-reinforced pile-supported (GRPS) embankments. Soil arching has been mostly investigated using trapdoor tests under soil self-weight and/or uniform surcharge. In real applications, localized surface loading, such as traffic loading, may be applie...

Given the limit studies on the behavior of GRPS embankments with different numbers of geosynthetic layers and pile caps in a triangular pattern, this paper conducted a series of three-dimensional (3-D) numerical analyses. The numerical model was verified based on a well-instrumented large-scale test. A 3-D soil arch model was proposed for pile caps...

The simplified GRC proposed by the writers can be adequately used to describe the progressive development of two-dimensional soil arching with displacement. The simplified GRC requires fewer parameters than the original GRC. The simplified GRC includes three basic (control) points of the original GRC; therefore, the simplified GRC can describe the...

Buried structures, such as pipes and culverts, installed under low embankments, are subjected to surface loading and additional stresses are transferred from their surrounding soil due to negative soil arching. Higher stresses on a buried structure may cause excessive deformations and even failure of the structure. The Induced Trench Installation (...

In this study, both two-dimensional (2D) and three-dimensional (3D) numerical analyses were carried out to evaluate the performance of geosynthetic-reinforced soil (GRS) piers. The numerical models were first calibrated and verified against test results available in the literature. A parametric study was then conducted under both 2D and 3D conditio...

Buried structures, such as pipes and culverts, are extensively used for transportation applications. The existence of these structures within the soil mass causes a redistribution of stresses. The stiffness of the buried structure relative to the surrounding soil affects the magnitude and distribution of vertical stresses. Higher stresses on a buri...

Loss of soil particles due to mineral dissolution, degradation or internal erosion can lead to a change in the microstructure of soil, which as a result, affects the strength and stiffness of soil. This paper presented an approach to investigate the behavior of granular soil subjected to local particle removal by introducing a certain amount of ero...

A special device was designed, manufactured, and used to create a three-dimensional (3D) layout of rigid supports to investigate the spatial tensile behavior of the geosynthetic reinforcement material over rigid supports. A polyester (PET) sheet was used to simulate the geosynthetic reinforcement material. The results from the model tests using thi...

Piping erosion-induced earthen structure failures can cause catastrophic consequences and great economic loss. Experimental laboratory simulation of piping plays a key role for the study of eroded soils. Up till now, piping erosion has been simulated in different ways, such as artificial slot or drilled hole. This paper is a continuation of such ef...

The dynamic assessment of a saturated reinforced-soil retaining wall (SRS-RW) has drawn considerable interest as several partial or full collapses of retaining walls due to earthquakes occurring during or immediately after heavy rains have been reported. In this study, a centrifuge shaking table test of the dynamic performance of a SRS-RW, in which...

Soil arching exists in many geotechnical applications, including Geosynthetic-Reinforced Pile-Supported (GRPS) embankments. Soil arching is associated with pressure distribution on and between piles at different levels of differential settlement resulting from the stiffness difference between soil and piles. When GRPS embankments are used for high...

Soil arching is a phenomenon describing stress re-distribution due to relative movement between adjoining portions. It commonly exists when soil interacts with structure elements, for example, tunnels, retaining walls, buried structures, and piles in pile-supported embankments. A yielding or ultimate state of soil (i.e., the shear stress in soil is...

Soil arching is a phenomenon describing stress re-distribution due to relative movement between adjoining portions. It commonly exists when soil interacts with infrastructure, for example, tunnels, retaining walls, buried structures, and pilesupported earth structures. A yielding state of soil (i.e., the shear stress in soil is equal to its shear s...

In cases where the space available for the mechanically stabilized earth (MSE) walls is less than required, the “narrowed mechanically stabilized earth walls” are usually designed and constructed next to the existing stable slopes/walls. Although such walls have already been used and studied in some projects, the effects of different interface conn...

In this paper, a shaking table test on the seismic performance of SRW was simulated systematically with dynamic finite element method. In the analysis, a cyclic mobility model, in which the influences of the stress-induced anisotropy, the density and the structure of the soil can be described in a unified way, was adopted to simulate the backfilled...

A wall of mechanically stabilized earth (MSE) with large concrete panel facing, reinforced with polyester straps, is an emerging technology in the United States. To enable the design of this wall system through AASHTO's methodology, the system's classification of extensibility must be established. Therefore, a section of such a wall was instrumente...

High-energy impact rollers (IR) have been increasingly used for earthworks by compacting on-site soils. The IR applies high energy to the ground and densifies deeper soils than conventional rollers and plate-type compactors. A trial program was implemented on the third runway of the Shanghai Pudong International Airport in China to validate the per...

A laboratory investigation of the influence of different factors - including weight, size and towing speed of impact modules - on the effectiveness of impact roller (IR) compaction was carried out. An impact roller simulation device was developed to do the investigation and air pluviation technique was used to prepare loose, dry, sand specimens. Th...

Basing on the foundation treatment project of the beach area of Baosteel and considering the effect of dredger fill and miscellaneous fill on the consolidation behavior, the whole consolidation process of the foundation was studied with Plaxis program, and the results were validated by the monitor data. It is concluded that the excess pore pressure...

The mechanical properties of soil-reinforcement interaction are of utmost importance for the design and stability analysis of reinforced soil structures. Using large-multifunctional interface shear apparatus, a series of horizontal cyclic shear tests are carried out between geogrid and standard sand. The mechanical behavior of geogrid-soil interfac...

To investigate the driving effect of long pre-stressed high-strength concrete (PHC) pipe piles on surrounding cohesive soil layers and mixed soil layers, standard penetration tests and static cone penetration tests were performed. Pore water pressure, lateral displacement in the surrounding soils and shaft forces along the piles were also measured....

Grouted rockbolts are widely used in tunneling excavation. However, the rockbolt design is still basically empirical, the mechanical behavior of grouted rockbolts, especially the interfacial behavior, has never been studied systematically. First of all, a tri-linear bond slip model is proposed for modeling the rockbolt interfacial behavior. Then an...

A new ground improvement method is proposed for embankment foundation on soft soils, involving the use of both soil–cement columns and prefabricated vertical drains (PVDs) to improve the shear strength and accelerate the pre-consolidation process. An analytical solution was derived for calculating the consolidation process of this composite foundat...

The total pullout resistance of geogrid in a soil includes two components: (1) the interface friction resistance that takes place along longitudinal ribs and (2) the passive resistance that takes place against the front of transverse ribs. A series of pullout tests and analyses were conducted to quantify the contributions of the above two component...

Salt-rich soft soils have not only general characteristics of common soft soils, but also contain high contents of Mg2+, Cl−, and SO42−, which have negative effects on deep mixing method using cement to treat soft soils. Laboratory and field tests were conducted to investigate the effects of changing cement incorporating ratio, water content, cemen...