Shear strength characterization of municipal solid waste at the Suzhou landfill, China

The current practice of slope stability analysis for a municipal solid waste (MSW) landfill usually overlooks the dependence of waste properties on the fill age or embedment depth. Changes in shear strength of MSW as a function of fill age were investigated by performing field and laboratory studies on the Suzhou landfill in China. The field study included sampling from five boreholes advanced to the bottom of the landfill, cone penetration tests and monitoring of pore fluid pressures. Twenty-six borehole samples representative of different fill ages (0 to 13 years) were used to perform drained triaxial compression tests. The field and laboratory study showed that the waste body in the landfill can be sub-divided into several strata corresponding to different ranges of fill age. Each of the waste strata has individual composition and shear strength characteristics. The triaxial test results showed that the MSW samples exhibited a strain-hardening and contractive behavior. As the fill age of the waste increased from 1.7 years to 11 years, the cohesion mobilized at a strain level of 10% was found to decrease from 23.3 kPa to 0 kPa, and the mobilized friction angle at the same strain level increasing from 9.9° to 26°. For a confinement stress level greater than 50 kPa, the shear strength of the recently-placed MSW seemed to be lower than that of the older MSW. This behavior was consistent with the cone penetration test results. The field measurement of pore pressures revealed a perched leachate mound above an intermediate cover of soils and a substantial leachate mound near the bottom of the landfill. The measurements of shear strength properties and pore pressures were utilized to assess the slope stability of the Suzhou landfill.     

2002年CT扫描和三维成像学术年会评述

由CT理论与应用研究编辑部和北京信息工程学院主办、有中国体视学学会多位理事和会员参加的“2002年CT扫描和三维成像研讨会（CT科技学术年会）”于2002年10月18－20日，在北京大学逸夫苑理科楼学术报告厅举行。中国体视学学会副理事长刘国权教授出席致辞，对于这次CT科技年会的召开表示祝贺，并介绍了2003年在美国圣迭戈和北京将要召开第11届国际体视学会大会的有关情况，希望有关专家准备论文出席，来自全国各地48位专家，教授出席了会议，本次会议涉及CT理论、计算方法和软件及硬件技术；医学CT扫描成像和疾病诊断；工业CT和三维成像：地球层析和工程CT。美国爱荷华大学王革教授，纽约罗彻斯特大学宁若拉教授专程到会，分别做了精彩的特邀主题报告：显微CT的锥束重建新方法和近年来在这方面的进展和展望”，“锥光束三维CT技术在美国的过去、现在和未来”“国内专家也报告了前沿研究的新成果，在会前，CT理论与应用研究编辑部，根据收到的论文和摘要汇编和印制了专集，在会议最后一天，召开了“CT理论与应用研究”期刊编委会，传达了中国科协对于办好科技期刊的新要求，会议开得很成功。     

Evaluation of liquefaction potential using neural-networks and CPT results

In this research, a reliable Cone Penetration Test data set was gathered with a wide range of parameters. This data was incorporated in a Neural-Networks computer software called STATISTICA Neural-Networks. The back propagation algorithm with a multilayer perceptron network is utilized to analyze the liquefaction occurrence in different sites. In this study, different sets of effective parameters for the neural-network analyses are selected such that to reduce the noise and to obtain more accurate results.Considering the relative importance of effective parameters in liquefaction assessment, it is indicated that σ₀, σ′₀ together play a more important role than what previously was assumed and hence the relative importance of the q_c and seismic parameters are decreased compared with the previous works. The results presented here have more accuracy than previous works while at the same time, the range of the parameters used in this study is much wider than what was previously used. This range of parameters makes the proposed method applicable for practical purposes.     

Evaluation of soil liquefaction in the Chi-Chi, Taiwan earthquake using CPT

During the 1999 Chi-Chi, Taiwan earthquake, many sand boiling phenomena were observed in central Taiwan, which caused severe ground settlement and structure damages. According to the installed accelerograms, the peak ground surface horizontal accelerations in the liquefaction-affected areas range from 774.42 to 121.3 gal. The writers carried out an extensive investigation of soil liquefaction in this earthquake. In this paper, we present results of the CPT exploration and post-earthquake liquefaction analysis. Two hundred and seventy five (275) cone penetration test data were collected from the liquefaction-affected areas, and 46 liquefaction case histories and 88 non-liquefaction case histories were derived that can be used to evaluate the accuracy of existing liquefaction evaluation models. In addition, the strength of the liquefied soils after earthquake and the implication of its liquefaction potential in the future event are discussed.     

Estimating severity of liquefaction-induced damage near foundation

An empirical procedure for estimating the severity of liquefaction-induced ground damage at or near foundations of existing buildings is established. The procedure is based on an examination of 30 case histories from recent earthquakes. The data for these case histories consist of observations of the damage that resulted from liquefaction, and the subsurface soil conditions as revealed by cone penetration tests. These field observations are used to classify these cases into one of three damaging effect categories, ‘no damage’, ‘minor to moderate damage’, and ‘major damage’. The potential for liquefaction-induced ground failure at each site is calculated and expressed as the probability of ground failure. The relationship between the probability of ground failure and the damage class is established, which allows for the evaluation of the severity of liquefaction-induced ground damage at or near foundations. The procedure presented herein represents a significant attempt to address the issue of liquefaction effect. Caution must be exercised, however, when using the proposed model and procedure for estimating liquefaction damage severity, because they are developed based on limited number of case histories.     

The penetration experiment to predict liquefaction resistance of reclaimed soils

The liquefaction resistance of the soils used to be estimated through the in situ tests, such as standard penetration test and cone penetration test; or by means of cyclic triaxial test in laboratory. However, both in situ tests and cyclic triaxial test are time-consuming and costly; this study introduces a quick and cost-effective method to evaluate the liquefaction resistance of soils under certain confining pressure in laboratory. A particular device modified from the conventional triaxial compression test apparatus, namely “Triaxial Cone Penetration Test”, was developed to obtain the peak values of cone resistance in soils so as to correlate the liquefaction resistance of the reclaimed soils evaluated by cyclic triaxial tests. The test result indicates a good correlation between the peak value of cone resistance and the corresponding cyclic stress ratio (CSR) at the state of initial liquefaction, in which the correlation for loose samples is better than that for dense samples. Besides, both peak values of cone resistance and corresponding CSR increase with fine content of soils reaches 10% and decreased with fine content varying between 10% and 50%. By examining the compositions of the soils with scanning electron microscopy and X-ray diffraction, it is found that the proportion and characteristics of the fines plays an important role on the liquefaction resistance of the reclaimed soils.     

基于孔压静力触探(CPTU)测试的连云港海相粘土前期固结压力确定方法研究

首先回顾了基于孔压静力触探(CPTU)测试确定前期固结压力的方法,通过连云港海相粘土场地进行的CPTU试验资料,以室内固结试验得到的前期固结压力作为参考值评估了经验方法预测前期固结压力的有效性。最简单的方法是直接建立前期固结压力和净锥尖阻力的关系,同时也是最有效的方法。     

The evolution of pore pressure fields around standard and ball penetrometers: influence of penetration rate

Rate effects are examined in the steady pore pressure distribution induced as a result of penetration of standard and ball penetrometers. The incompressible flow field, which develops around the penetrometer is used to define the approximate soil velocity field local to the penetrometer tip. This prescribes the Lagrangian framework for the migration of the fluid saturated porous medium, defining the advection of induced pore pressures relative to the pressure‐monitoring locations present on the probe face. In two separate approaches, different source functions are used to define the undrained pore fluid pressures developed either (i) on the face of the penetrometer or (ii) in the material comprising the failure zone surrounding the penetrometer tip. In the first, the sources applied at the tip face balance the volume of fluid mobilized by the piston displacement of the advancing penetrometer. Alternately, a fluid source distribution is evaluated from plasticity solutions and distributed throughout the tip process zone: for a standard penetrometer, the solution is for the expansion of a spherical cavity, and for the ball penetrometer, the solution is an elastic distribution of stresses conditioned by the limit load embedded within an infinite medium. For the standard penetrometer, the transition from drained to undrained behavior occurs over about two orders of magnitude in penetration rate for pore pressures recorded at the tip (U1) and about two‐and‐a‐half orders of magnitude for the shoulder (U2). This response is strongly influenced by the rigidity of the soil and slightly influenced by the model linking induced total stresses to pore pressures. For the ball penetrometer, the transition from drained to undrained behavior also transits two‐and‐a‐half orders of magnitude in penetration rate, although it is offset to higher dimensionless penetration rates than for standard penetration. Copyright © 2012 John Wiley & Sons, Ltd.     

Rapid delineation of subsurface petroleum contamination using the site characterization and analysis penetrometer system

 The Site Characterization and Analysis Penetrometer System (SCAPS) was used to investigate subsurface petroleum contamination at Aberdeen Proving Ground, Maryland. The SCAPS is a rapid site-screening tool developed by the Tri-Services (U.S. Army, Navy, and Air Force) to reduce the cost of installation restoration activities. The system, consisting of a geophysical cone penetrometer fitted with a laser-induced fluorescence petroleum sensor, is capable of simultaneous, real-time delineation of subsurface stratigraphy and petroleum contamination. Onsite processing of the SCAPS data allows three-dimensional visualization of both subsurface stratigraphy and petroleum contaminant distribution. The site investigation described herein successfully identified three distinct areas of subsurface petroleum contamination caused by leaking underground storage tanks containing No. 2 healing oil. The SCAPS petroleum sensor response was verified by obtaining 20 soil samples and performing onsite and conventional laboratory analyses for petroleum contaminants. Verification sample results indicate a strong correlation between the SCAPS fluorescence data and conventional measures of petroleum contamination. This investigation illustrates the capabilities of the SCAPS for rapid site characterization. Received: 27 November 1995 · Accepted: 11 December 1995