Liquefaction evaluation of dam foundation soils considering overlying structure

The liquefaction analysis procedure conducted at a dam foundation associated with a layer of liquefiable sand is presented. In this case, the effects of the overlying dam and an embedded diaphragm wall on liquefaction potential of foundation soils are considered. The analysis follows the stress-based approach which compares the earthquake-induced cyclic stresses with the cyclic resistance of the soil, and the cyclic resistance of the sand under complex stress condition is the key issue. Comprehensive laboratory monotonic and cyclic triaxial tests are conducted to evaluate the static characteristics, dynamic characteristics and the cyclic resistance against liquefaction of the foundation soils. The distribution of the factor of safety considering liquefaction is given. It is found that the zones beneath the dam edges and near the upstream of the diaphragm wall are more susceptible to liquefaction than in free field, whereas the zone beneath the center of the dam is less susceptible to liquefaction than in free field. According to the results, the strategies of ground improvement are proposed to mitigate the liquefaction hazards

Study on the horizontal bearing characteristics of pile foundation in coral sand

This paper presents the horizontal bearing characteristics of piles in coral sand and silica sand from comparative experimental studies. A total of 6 model piles with different diameters are tested. The horizontal bearing capacity, deformation characteristic, bending moment, p-y curve, the change in soil horizontal pressure, as well as the particle breakage behaviour of coral sand are investigated. The results show that, in coral sand foundation, the horizontal bearing capacities of piles and the increments of soil horizontal pressures are obviously greater than those in silica sand. Accordingly, the lateral displacement, the rotation of pile head, the bending moment and the corresponding distribution depth in coral sand are significantly smaller than that in silica sand. The p-y curves indicate that the horizontal stiffness of coral sand is greater than that of silica sand. Remarkably, the breakage behaviour of coral sand is mainly distributed in the range of 10 times pile diameter depth and 5 times pile diameter width on the side where the sand is squeezed by pile. Furthermore, in coral sand, the influence of pile size is more pronounced, the squeezing force generated by pile spread farther and its influence range is larger compared to those in silica sand.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Thermomechanical properties of sand–structure interface using temperature-controlled triaxial instrument

To study the effect of temperature on the mechanical properties of a sand–structure interface, a temperature-controlled interface shear test system based on a triaxial instrument was developed by placing a cylindrical structure inside a triaxial soil sample and connecting them to two individual thermostat water baths. Sand–aluminum interface shear tests under effective cell pressures of 50, 100, and 200 kPa and temperatures of 6, 19, 32, and 45 °C were carried out to evaluate the thermal effects on the interface strength under drained conditions. Constant vertical force–stiffness coupled with a thermal load applied to the aluminum top before the interface shearing was also considered. The results show that the new apparatus can serve a variety of thermomechanical load paths, including maintaining a constant rate of displacement and a constant vertical force–stiffness on the structure top prior to the shearing process. The apparatus also has advantages over other interface shear devices in controlling drainage conditions and measurement of volume change and excess pore pressure. A comparison with the previous literature on interface shear strength verifies the results in this study. Different thermomechanical load paths applied on the interface supplement the insignificant thermal effect on the sand–aluminum interface shear strength. However, it is the first time that the displacement of the aluminum is observed to be related to thermal variations and independent of the magnitude of the vertical force.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Undrained Cylindrical and Spherical Cavity Expansion in Elastic-Viscoplastic Soils

Various undrained cavity expansion solutions for elastic-plastic soil have been proposed previously. However, no solution has been presented for elastic-viscoplastic (EVP) soil until now. This paper presents a general solution method for solving the classical one-dimensional (1D) boundary value problem (BVP) for undrained cylindrical or spherical cavity expansion in EVP soil with an emphasis on the rate effect of soil. The solution method is summarized as three standard procedures: (a) obtaining the soil displacement and strain under incompressible conditions; (b) calculating the effective stress of soil through a suitable constitutive law; and (c) obtaining the pore pressure by numerically solving the stress equilibrium equation through the finite difference method (FDM) or other numerical solution techniques. The numerical algorithms for calculating the effective stress and pore pressure are very simple without any complex iteration processes, and they require little calculation time but provide high computational accuracy. In addition, some numerical results are given to investigate the influence of the cavity expansion velocity on the cavity expansion response. The proposed solution procedure is general and can be applied not only for the EVP model but also for other plasticity models, and the given EVP solution can be applied to interpret the rate effect of the CPT test and pile penetration.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

The Influence of Aging Population in Rural Families on Farmers’ Willingness to Withdraw from Homesteads in Shenyang, Liaoning Province, China

Population aging presents a significant global challenge. In China, the aging of the rural population coincides with inefficient rural homestead utilization. While the Chinese government has enacted policies to address this, their impact remains limited. Utilizing survey data from 403 rural families in Shenyang, Liaoning Province, China, this study applies the binary Logit and mediating effect models to analyze the impact of rural family population aging on farmers’ willingness to withdraw from homesteads with compensation and their compensation preference. Key findings include: (1) Family population aging intensifies farmers’ willingness to withdraw from homesteads, with a stronger preference for non-monetary compensation as aging increases. (2) Regarding the willingness to withdraw with compensation, farmers’ cognition of homestead security value masks the effect by 4.71%, while asset value cognition has no mediating effect. (3) With regard to promoting non-monetary compensation choices, farmers’ homestead asset value cognition fully mediates at 16.01%, but security value cognition is without mediating effect. Based on these findings, it is recommended that the government crafts tailored homestead withdrawal policies considering farmers’ family age structure. Further, efforts should aim at refining farmers’ understanding of homestead values, promoting a blend of non-monetary and monetary compensations

A systematic review of unilateral versus bilateral percutaneous vertebroplasty/percutaneous kyphoplasty for osteoporotic vertebral compression fractures

Objective: The aim of this study was to compare the unilateral and bilateral approaches in treating osteoporotic vertebral compression fractures. Methods: Based on the principles and methods of the Cochrane systematic reviews, the records of the Cochrane Library, PubMed, Web of Science, Chinese Bio-medicine database, China Journal Full-text Database, VIP database, and Wanfang database were reviewed until October 2014. The randomized controlled trials on unilateral and bilateral approaches to percutaneous vertebroplasty (PVP)/percutaneous kyphoplasty (PKP) for osteoporotic vertebral compression fractures were included. The risk of bias of included trials was assessed based on the Cochrane Handbook for Systematic Reviews of Interventions Version. The RevMan Software 5.0 was used for meta-analysis. Results: Fifteen randomized controlled trials with a total of 850 patients were included. Risk of bias in the included studies was inevitable. There was no statistically significant difference in visual analog scale, vertebral height, kyphotic angular, and quality of life. The main operative complications were bone cement leakage and adjacent vertebral fracture, without difference between the two groups. Conclusions: In view of the current evidence, there is insufficient evidence to show any difference between the unilateral and bilateral approaches in both the PVP and PKP treatment in osteoporotic vertebral compression fractures. Level of Evidence: Level I, Therapeutic study. Keywords: Minimally invasive surgery, Osteoporotic vertebral compression fracture, Percutaneous kyphoplasty, Percutaneous vertebroplasty, Systematic revie

Facile Synthesis of Fe3O4@Au/PPy-DOX Nanoplatform with Enhanced Glutathione Depletion and Controllable Drug Delivery for Enhanced Cancer Therapeutic Efficacy

The complex physiological environment and inherent self-healing function of tumors make it difficult to eliminate malignant tumors by single therapy. In order to enhance the efficacy of antitumor therapy, it is significant and challenging to realize multi-mode combination therapy by utilizing/improving the adverse factors of the tumor microenvironment (TME). In this study, a novel Fe3O4@Au/PPy nanoplatform loaded with a chemotherapy drug (DOX) and responsive to TME, near-infrared (NIR) laser and magnetic field was designed for the combination enhancement of eliminating the tumor. The Fe2+ released at the low pH in TME can react with endogenous H2O2 to induce toxic hydroxyl radicals (·OH) for chemodynamic therapy (CDT). At the same time, the generated Fe3+ could deplete overexpressed glutathione (GSH) at the tumor site to prevent reactive oxygen species (ROS) from being restored while producing Fe2+ for CDT. The designed Fe3O4@Au/PPy nanoplatform had high photothermal (PT) conversion efficiency and photodynamic therapy (PDT) performance under NIR light excitation, which can promote CDT efficiency and produce more toxic ROS. To maximize the cancer-killing efficiency, the nanoplatform can be successfully loaded with the chemotherapeutic drug DOX, which can be efficiently released under NIR excitation and induction of slight acidity at the tumor site. In addition, the nanoplatform also possessed high saturation magnetization (20 emu/g), indicating a potential magnetic targeting function. In vivo and in vitro results identified that the Fe3O4@Au/PPy-DOX nanoplatform had good biocompatibility and magnetic-targeted synergetic CDT/PDT/PTT/chemotherapy antitumor effects, which were much better than those of the corresponding mono/bi/tri-therapies. This work provides a new approach for designing intelligent TME-mediated nanoplatforms for synergistically enhancing tumor therapy

A modified analytical solution of soil stress distribution for XCC pile foundations

X-section cast-in-place concrete pile (XCC pile) is a new type of pile foundation, which has an X-shaped cross section. Compared to the traditional circular pile of the same cross-sectional area, the bearing capacity of an XCC pile is higher due to increased cross-sectional perimeter. Since Geddes solution is based on St. Venant's principle, leading to the results independent of the cross-sectional geometry and size, large differences are induced when estimating the soil stress distribution for XCC pile foundations. This paper derives a modified analytical solution, which is dependent on the cross-sectional geometry of XCC pile, from Geddes solution. Validation of this modified solution was conducted through three-dimensional numerical analysis and proven more suitable for XCC pile foundations. Parametric study on three geometrical parameters is conducted using this modified solution. The results indicate that the stress in founding soil due to skin friction decreases with increasing pile radius and central angle of concave, but increases with increasing length of flat side. The stress due to end-bearing decreases with increasing pile radius and length of flat side, but increases with increasing central angle of concave. From the parametric studies, the recommended dimensions of XCC pile radius, length of flat side, and central angle of concave are recommended ranges from 200 to 600 mm, 30 to 60 mm, and 90 degrees to 150 degrees, respectively.GUNAWAN, Anthony, CIVL, SENG, HKUST. [email protected]