Suction-Monitored Direct Shear Testing of Residual Soils from Landslide-Prone Areas

The apparent cohesion due to soil suction plays an important role in maintaining the stability of steep unsaturated soil slopes with deep ground water table. In this paper, a modified direct shear box is used to determine the relationships between the value of this additional cohesion and the associated soil suction. The apparatus incorporates a miniature tensiometer which allows for the simple and direct measurement of suction during shearing. The soil-water characteristic curves and shearing behavior of intact residual soils, being low-to-medium plasticity silts, as well as silty sand, taken from four landslide-prone areas in Thailand, have been investigated. The relatively low air-entry suctions (0–7 kPa) and bimodality of the soil-water characteristic curves gives an indication of the structured pore size distribution of the materials tested. Samples with higher suction tend to display stronger bonding at particle contacts and thus are more brittle. The shear strength is found to increase nonlinearly with suction, though linearization can be reasonably assumed for suction below around 30 kPa. Prediction of shear strength based on soil-water characteristic curves agrees better with ultimate than peak values. A simple equation is proposed for the minimum ultimate strength that can be expected in an unsaturated residual soil with a suction lower than about 30 kPa.     

Clean up of Petroleum-Hydrocarbon Contaminated Soils Using Enhanced Bioremediation System: Laboratory Feasibility Study

The objective of this study was to assess the potential of applying enhanced bioremediation on the treatment of petroleum-hydrocarbon contaminated soils. Microcosm experiments were conducted to determine the optimal biodegradation conditions. The control factors included oxygen content, nutrient addition, addition of commercially available mixed microbial inocula, addition of wood chip and rice husk mixtures (volume ratio = 1:1) as bulking agents, and addition of organic amendments (chicken manures). Results indicate that the supplement of microbial inocula or chicken manures could significantly increase the microbial populations in soils, and thus enhance the efficiency of total petroleum hydrocarbon (TPH) removal (initial TPH = 5,500?mg/kg). The highest first-order TPH decay rate and removal ratio were approximately 0.015?day?1 and 85%, respectively, observed in microcosms containing microbial inocula (mass ratio of soil to inocula = 50:1), nutrient, and bulking agent (volume ratio of soil to bulking agent = 10 to 1) during 155 days of incubation. Results indicate that the first-order TPH decay rates of 0.015 and 0.0142?day?1 can be obtained with the addition of microbial inocula and chicken manures, respectively, compared with the decay rate of 0.0069?day?1 under intrinsic conditions. Thus, chicken manures have the potential to be used as substitutes of commercial microbial inocula. The decay rate and removal ratio can be further enhanced to 0.0196?day?1 and 87%, respectively, with frequent soil shaking and air replacement. Results will be useful in designing an ex situ soil bioremediation systems (e.g., biopile and land farming) for practical application.     

Seismic Displacement Criterion for Soil Retaining Walls Based on Soil Strength Mobilization

This paper presents a seismic displacement criterion for conventional soil retaining walls based on the observations of a series of shaking table tests and seismic displacement analysis using Newmark’s sliding-block theory taking into account internal friction angle mobilization along the potential failure line in the backfill. A novel approach that relates the displacement of the wall and the mobilized friction angle along the shear band in the backfill is also proposed. A range of horizontal displacement-to-wall height ratios (δ3h/H) between 2 and 5% representing a transitional state from moderate displacement to catastrophic damage were observed in the shaking table tests on two model retaining walls. This observation is supported by both Newmark’s displacement analysis and a new approach that relates the movement of the wall to the mobilization of the friction angle along the shear band in the backfill. A permissible displacement of the wall as defined by the displacement-to-wall height ratio, namely, δ3h/H, equal to 2% was found to be of practical significance in the sense that peak friction angle of the investigated sand is retained along the shear band in the backfill. It is also suggested that δ3h/H = 5% be used as a conservative indicator for the onset of catastrophic failure of the wall associated with fully softened soil strength along the shear band in cohesionless backfill.     

废树脂苯乙烯固化研究(Ⅱ)

本文研究废离子交换树脂苯乙烯固化的工艺条件和固化产品性能鉴定。该法能包容62％(W)废树脂。固化产品均匀、坚韧、抗压强度239kg/cm~2。在去离子水中浸泡120d,浸出率对于~(137)Cs为10~(-6)cm/d,对于~(60)Co和~(85)Sr为10~(-7)-10~(-8)cm/d。长期水浸不溶胀。承受辐照剂量>10~8rad。闪点270℃,燃点290℃左右。加热到450℃不自燃,DTA曲线上235℃前无放热峰。     

浮选柱处理滇池污水的工艺初探

针对滇池水污染的状况和治理现状，对目前国内采用ICEAS工艺的污水处理厂脱氮除磷效果不佳的现状，此工艺采用浮选柱作为浮选设备，并采用充以臭氧等新的技术，能更有效地解决滇池污水中的氮、磷、有机悬浮物、COD污染物，预计会有很好的研究价值和应用前景。     

Analytical and Numerical Modeling of Soft Soil Stabilized by Prefabricated Vertical Drains Incorporating Vacuum Preloading

This paper describes the analytical formulation of a modified consolidation theory incorporating vacuum pressure, and numerical modeling of soft clay stabilized by prefabricated vertical drains, with a linearly distributed (trapezoidal) vacuum pressure for both axisymmetric and plane strain conditions. The effects of the magnitude and distribution of vacuum pressure on soft clay consolidation are examined through average time-dependent excess pore pressure and consolidation settlement analyses. The plane strain analysis was executed by transforming the actual vertical drains into a system of equivalent parallel drain walls by adjusting the coefficient of permeability of the soil and the applied vacuum pressure. The converted parameters are incorporated in the finite element code ABAQUS, employing the modified Cam-clay theory. Numerical analysis is conducted to study the performance of a full-scale test embankment constructed on soft Bangkok clay. The performance of this selected embankment is predicted on the basis of four different vacuum pressure distributions. The predictions are compared with the available field data. The assumption of distributing the vacuum pressure as a constant over the soil surface and varying it linearly along the drains seems justified in relation to the field data.     

概率神经网络及其在岩土类别判定中的应用

概率神经网络是一种由径向基函数神经网络和竞争神经网络组合而成的新型神经网络,适用于分类和模式识别。本文首先简单介绍了概率神经网络的基本原理,然后通过两个实例对概率神经网络的可行性进行了验证,其分类结果是合理的、可信的。     

基于MODIS和AMSR-E遥感数据的土壤水分降尺度研究

微波传感器获得的土壤水分产品空间分辨率一般都很粗,而流域尺度上的研究需要中高分辨率的土壤水分数据。用MODIS逐日地表温度产品MOD11A1和逐日地表反射率产品MOD09GA构建温度-植被指数特征空间,并计算得到TVDI(Temperature Vegetation Dryness Index)指数,它与土壤水分呈负相关关系,能够反映土壤水分的空间分布模式,但并不是真实的土壤水分值。在AMSR-E像元尺度上求得TVDI与土壤水分的负相关系数,进而对VUA AMSR-E土壤水分产品进行降尺度计算得到0.01°分辨率的真实土壤水分值。经NAFE06(The National Airborne Field Experiment 2006)试验地面采样数据验证,降尺度后的土壤水分均方根误差平均值为6.1%。     

玉米/蒜苗套作系统中土壤微生物和土壤酶状况分析

对玉米蒜苗套作根区进行隔膜、隔网和无隔处理以及各自单作处理,通过处理间的相互比较,分析影响套作产量的主要土壤因素。结果表明:套作蒜苗土壤微生物上升其主要原因是根系间的非接触物质交换;套作玉米除此外,地上部环境的改变也使根部土壤微生物数量上升。根系间的非接触效应还使蒜苗、玉米土壤过氧化氢酶、蔗糖酶活性提高,而环境因素的改变也使玉米过氧化氢酶,蒜苗脲酶活性提高。相关性分析表明:微生物对蒜苗根际土壤酶活性的影响大于对玉米土壤酶的影响。     

The Effects of Cryogenic Treatment on the Thermal Conductivity of GRCop-84

The mechanical properties of many materials have been enhanced via cryogenic treatment, which is a cold temperature process performed after traditional heat treatment. In this research the effect of cryogenic treatment on GRCop-84 was examined. Cryogenically and non-cryogenically treated samples were tested identically to determine whether cryogenic treatment has a significant affect on the thermal conductivity of GRCop-84. Optical and electron microscopy were used to characterize the material properties. Cryogenic treatment includes a temper that appears to be responsible for the enhancements observed in GRCop-84.