Qingsheng Chen

Determination of active earth pressure on rigid retaining wall considering arching effect in cohesive backfill soil

AbstractA new simplified method is proposed to compute the active earth pressure acting on the backface of a rigid retaining wall undergoing horizontal translation. The effect of soil arching for cohesive backfill soil and friction mobilized along the wall–soil interface was considered. Analytical expressions to determine the slip surface angle and the coefficient of active earth pressure were obtained using the limit-equilibrium approach. These expressions were used for the horizontal flat-element method to obtain theoretical formulas for the active earth pressure, active thrust, and its point of application. Additionally, an implicit solution was derived for the depth of the tension crack in the backfill. A parametric study was undertaken to assess the effects of cohesion, unit weight, friction angle, surcharge pressure, and wall–soil friction angle on the active earth pressure, as well as the effects of the friction angle of backfill soil and wall–soil friction angle on the slip surface angle. The resu...

Deformation Behavior of Lignosulfonate-Treated Sandy Silt under Cyclic Loading

AbstractAlthough many traditional soil stabilizers (e.g., lime, cement, gypsum, and fly ash) have been widely and effectively used for ground improvement, they often adversely affect the surrounding soil and groundwater environment. Moreover, traditionally treated soils have shown excessive brittle behavior, especially under cyclic loads, which is often undesirable for structures such as rail embankments and airport runways. To establish an alternative stabilizer that could overcome these problems, this paper presents the results of a series of cyclic triaxial tests on the use of lignosulfonate (a by-product of the timber industry), an environmentally friendly soil stabilizer effective for treating fine sandy silt that formed the bulk of the embankment fill at Penrith, Australia. The influence of lignosulfonate on the stress-strain behavior, resilient modulus, and excess pore pressure development of the treated soil is discussed.

Estimation of Passive Earth Pressure against Rigid Retaining Wall Considering Arching Effect in Cohesive-Frictional Backfill under Translation Mode

AbstractIn this study, a novel analytical approach is proposed to calculate the passive earth pressure against a rigid retaining wall subjected to the translation mode. Effects of arching in cohesive backfill soils as well as friction mobilized along the wall–soil interface are considered. Analytical expressions of the earth pressure, passive resistance, and its height of application on the backface of the retaining wall were derived based on static equilibrium of forces under passive conditions acting on the failure wedge. A parametric study was undertaken to assess effects of internal friction angle of backfill, wall–soil interface friction angle, surcharge pressure, cohesion, unit weight, and inclination angle of the slip surface on the active earth pressure as well as on the slip-surface angle. The results of the proposed method were then verified against the existing test data as well as the predictions by Coulomb theory and Rankine theory. The results show that the proposed method yields satisfactor...

Effect of a cement-lignin agent on the shear behavior of Shanghai dredged marine soils

ABSTRACT With the rapid urbanization in Shanghai, China, suitable fill materials have been reported to be in great shortage in recent years. A prospective solution to these issues is to convert the huge amount of existing dredged marine soils to construction materials via solidification. However, there have been no studies on the shear behavior of solidified dredged materials from Shanghai region so far, while it has been reported by various researchers that the available data obtained from certain types of clay cannot be confidently and readily applied to other types of soils. To address this challenging issue, in this article, samples of Shanghai marine dredged soils were retrieved from the world’s largest reclamation project in Shanghai Lin-gang New City. A series of laboratory tests have been conducted to investigate the shear behavior of Shanghai dredged marine soils solidified using a new composite curing agent made of cement and lignin. The test results and the effect of this cement–lignin agent on the shear behavior of Shanghai marine soils, including the stress–strain behavior, shear strength properties, and failure characteristics are presented and discussed, which can provide valuable reference for the use of dredged soils as construction materials in the Shanghai region.

Limit analysis approach for accessing stability of three-dimensional (3-D) slopes reinforced with piles

ABSTRACT The stabilization of slopes by placing piles is one of the most innovative and effective slope reinforcement techniques in the coastal engineering in recent years. Due to the simplicity and efficiency, limit analysis method is the most common approach for assessing the stability of slopes. However, the majority of existing limit analysis methods is limited to slope without the presence of piles. In this technical note, a novel upper-bound limit analysis method was proposed to access the stability of three-dimensional slopes reinforced with piles incorporating the admissible rotational failure mechanism where toe failure, face failure, and base failure were taken into account. The effects of key designing parameters, e.g., pile location, pile spacing, slope angle, slope width on the stability of earth slopes, and geometry of critical slip surface were presented and discussed. The results demonstrate that the proposed approach is more appropriate for assessing the stability of slopes reinforced with piles and can be also utilized in the design of piles stabilizing the unstable slopes.

Elastoplastic solution for spherical cavity expansion in modified Cam-clay soil under drained condition

AbstractThis paper presents an innovative semianalytical solution for the expansion of a drained spherical cavity with finite initial radius. The widely known modified Cam-clay model is adopted to ...

Zoning of confined aquifers inrush and quicksand in Shanghai region

Groundwater inrush and quicksand from the underlying aquifers are two typical geological hazards during underground constructions in Shanghai region, China. The objective of this work is to give a zoning study on confined aquifers and quicksand geology in Shanghai region and provide helpful decision-making information for the government, urban planners and designers. The hydrogeological characteristics of the confined aquifers in Shanghai are collected, and two different criteria are then proposed for mapping the aquifers. The characteristics and distribution of the soil stratum, in which quicksand would occur, are then presented, and an index system for quicksand hazard and vulnerability assessment is proposed. Furthermore, the quicksand risk in different zones of Shanghai is evaluated using a semiquantitative approach, and the management zoning is developed by considering the urban planning of Shanghai. The zoning maps of confined aquifers and quicksand risk are obtained, and the high-risk zone can be directly identified from the zoning maps. This is greatly helpful for the future urban planning and underground constructions in Shanghai region. The proposed method for quicksand hazard and vulnerability assessment is also applicable for other cities undergoing geological hazards caused by confined water inrush and quicksand.

A new mixing technique for solidifier and dredged fill in coastal area

ABSTRACT One of the major drawbacks of the conventional method of land reclamation, which involves mixing cement with the dredged soils at the disposal site, is the high cost associated with its manufacturing and transportation. In this study, a new solidified dredged fill (SDF) technique and a new additive are proposed and their practical applications are discussed. Unlike the conventional approach, the dredged marine soils were mixed with the solidifiers using a newly designed mixing technique prior to its transport to site, which would significantly reduce the cost of site machinery and effectively reclaim land with adequate engineering properties necessary for the construction of infrastructure. To evaluate the performance of the reclaimed land using the proposed technique, a series of laboratory and field tests (namely, static and dynamic cone penetration tests, and plate load tests) were conducted on grounds filled with and without solidified dredged marine soils, respectively. The results showed that the engineering behavior of the reclaimed land with dredged marine soils using SDF technique had significantly improved. The SDF technique combined with the newly designed mixing system improved the performance of ground and has thus proved to be both cost-effective and safe.