Dynamic response of a non-circular lined tunnel with visco-elastic imperfect interface in the saturated poroelastic medium

A semi-analytical method is proposed to investigate the dynamic response of a non-circular tunnel with visco-elastic imperfect interface in poroelastic medium. Biot’s dynamic theory is used to simulate the saturated poroelastic medium, and the governing equations are solved by reducing them into three Helmholtz equations that the potential functions satisfy. The visco-elastic interface model with elastic and viscosity coefficients is adopted to analyze the interface effect around the non-circular lined tunnel. The analytic solutions of displacements and stresses are expanded in terms of wave functions. Some numerical examples are provided to analyze the effect of visco-elastic interface on the dynamic stress around the tunnel.     

Advances in Air Sparging Technology of Saturated Zone

In situ air sparging involves injecting atmospheric air, under pressure, into the saturated zone to remove those volatile and semi-volatile organic groundwater contaminants and to promote their biodegradation by increasing subsurface oxygen concentrations. Due to the advantages of low cost, high efficiency and in situ constructability, groundwater Air Sparging (AS) technology has been quickly developed in the world recently. Based on the explanation of its remediation principle, literature review is done on the research advancement of air sparging technology mainly from three aspects. First, various methods for determination of the zone of influence and visualization techniques of air flow forms during air sparging are summarized. Then the influence of environmental geological conditions and construction technology parameters on the remediation effect of air sparging is systematically analyzed. Thereafter, two main types of air sparging theoretical models including lumped-parameter model and multiphase fluid flow model are discussed respectively in detail. Finally, based on the problems and difficulties existing in present research and engineering practice, several future tasks such as the enhancement remediation techniques in complex geological sites, microscopic intrinsic mechanisms, and establishment of related design and construction standards which require to be done are briefly analyzed.     

Evaluation of hydraulic conductivity through particle shape and packing density characteristics of sand–silt mixtures

Abstract

This study aims to evaluate the relationship between saturated hydraulic conductivity with particle shape and packing density characteristics of silty sand soils. The article presents a series of hydraulics tests performed on three kinds of sand with different particles shapes (Chlef rounded sand, Fontainebleau sub-rounded sand and Hostun sub-angular sand) mixed with low plastic rounded Chlef silt in the range of 0–30% fines content. The sand–silt mixture samples were tested in the constant-head permeability device at a loose relative density (D_r = 18%) and a constant room temperature (T?=?20?°C). The obtained results indicate that the measured saturated hydraulic conductivity (K_s) correlates very well with the fines content (F_c), packing density in terms of [maximum void ratio “e_max,” minimum void ratio “e_min,” predicted maximum void ratio “e_max”_pr and predicted minimum void ratio “e_min”_pr] and particle shape characteristics ratios in terms of roundness ratio (R_r = R_hs/R_mixture) and sphericity ratio (S_r = S_hs/S_mixture) of the silty sand materials under consideration. Moreover, the analysis of the available data show a noticeable success in exploring the prediction of the saturated hydraulic conductivity (K_s) based on the particle shape and packing density characteristics (R_r, S_r, e_max, and e_min) of the studied sand–silt mixture samples.     

饱和土中浅圆弧状埋置基础对平面P波散射解答

在Biot饱和多孔介质动力学理论的基础上,利用Fourier—Bessel级数展开法,首次得到饱和土中浅圆弧状埋置基础对平面波散射问题的解答．并利用该解对有埋置基础的饱和土场地地面运动的幅值及其分布进行分析,研究了基础弹性对平面P波作用下饱和土地基与基础动力相互作用的影响。