Desiccation of a Clay by Grass,Bushes and Trees

After reviewing the past 60 years of research into the desiccation of clay soils by grass, bushes and trees as it affects shallow building foundations and roads pavements, it was concluded that most past research has been opportunistic and unplanned. Also, no attempt has been made to relate changes of soil water content to rainfall and rates of evapotranspiration. The paper reports the second stage of a sustained programme to observe and understand seasonal and annual changes of soil water content under grass and adjacent to bushes and trees. A 12 months set of two-monthly soil water content contours is presented together with the associated soil water balance, and a method is described for assessing evapotranspiration by bushes and trees by means of a solar energy balance.     

An Analytical Model for the Indentation of Rocks by Blunt Tools

Summary A methodology based on the cavity expansion model is developed to analyze the indentation of rocks by a class of blunt indenters. The analysis covers the particular self-similar case of indentation by blunt wedges or cones. As an example, the main results for the indentation of rocks by a spherical tool are presented and the analytical solution is compared with experimental results obtained by indenting a sphere in Harcourt granite.     

Indentation of a continent with a built-in thickness change: experiment and nature

Orogens oblique to the direction of plate convergence are currently attributed to obliquity between the margins of one or both of the sutured continents to their direction convergence. We use a single analogue experiment and natural examples to illustrate a potential additional factor: variations in strength of the indented continent at a high angle to the convergence direction. The wavelengths of structures in laterally shortened lithosphere depend on the strength of the most competent layers. Lateral variations in crustal thickness must therefore lead to structures oblique to any applied lateral compression.

An analogue experiment was performed to explore this phenomenon. A two-layer ‘indented continent’ was modelled by a brittle upper crust of sand above a lower crust of high-viscosity polymer floating on a single layer of low-viscosity syrup representing the mantle. The well-known strike-slip structures allowing lateral escape to distant weak boundaries were hindered by lateral boundaries in front of the indenter. This allowed us to focus on the effects of a thickness change built into the ‘indented continent’ along a zone parallel to the direction in which a vertical rigid wall advancing at a steady rate represented the indenter. Vertical escape led to an ‘orogenic belt’ oblique to the advancing wall; this obliquity influences subsequent lateral escape. Model scaling and interpretations are based on Extended Thin Sheet Approximation (ETSA) and standard theories of faulting.

Four sectors of the Alpine–Himalayan orogen (Iran, Tunisia, the Eastern Alps and the Himalaya) are oblique to the continental convergence direction, and we point to thickness changes at high angles to the suture that may account for this geometry. As crustal thicknesses north of oblique sectors of the Himalayas are not yet known, we speculate on them.

We infer from the main difference between our experiment and all our examples chosen from nature that vertical orogenic escape was oblique to our model suture but can be parallel to natural sutures.     

Indentation of a free‐falling lance penetrometer into a poroelastic seabed

A solution is developed for the build‐up, steady and post‐arrest dissipative pore fluid pressure fields that develop around a blunt penetrometer that self‐embeds from freefall into the seabed. Arrest from freefall considers deceleration under undrained conditions in a purely cohesive soil, with constant shear strength with depth. The resulting decelerating velocity field is controlled by soil strength, geometric bearing capacity factors, and inertial components. At low impact velocities the embedment process is controlled by soil strength, and at high velocities by inertia. With the deceleration defined, a solution is evaluated for a point normal dislocation penetrating in a poroelastic medium with a prescribed decelerating velocity. Dynamic steady pressures, P_D, develop relative to the penetrating tip geometry with their distribution conditioned by the non‐dimensional penetration rate, U_D, incorporating impacting penetration rate, consolidation coefficient and penetrometer radius, and the non‐dimensional strength, N_D, additionally incorporating undrained shear strength of the sediment. Pore pressures develop to a steady peak magnitude at the penetrometer tip, and drop as P_D=1/x_D with distance x_D behind the tip and along the shaft. Peak induced pressure magnitudes may be correlated with sediment permeabilities, post‐arrest dissipation rates may be correlated with consolidation coefficients, and depths of penetration may be correlated with shear strengths. Together, these records enable strength and transport parameters to be recovered from lance penetrometer data. Penetrometer data recorded off La Palma in the Canary Islands (J. Volcanol. Geotherm. Res. 2000; 101 :253) are used to recover permeabilities and consolidation coefficients from peak pressure and dissipation response, respectively. Copyright © 2004 John Wiley & Sons, Ltd.     

四氯化碳重液法分离蒙脱石

提出了一种新的蒙脱石重液分离方法,蒙脱石在正辛胺水溶液中浸过后,密度降至１．６０×１０３ｋｇ／ｍ３以下,可用ＣＣｌ４作重液实现与其它粘土矿物及杂质的分离。用７．５ｍｏｌ／ＬＮａＯＨ溶液处理此含有正辛胺的蒙脱石,可得纯度很高的钠蒙脱石。用此法进行蒙脱石定量分析,所得结果与国际铸造协会推荐的溴仿酒精重液法相符合,且成本低、操作方便、污染小。     

Geotechnical characterization of a landslide in a Blue Clay slope

This paper describes the results of an experimental, as well as theoretical, analysis of a landslide in a clay slope at the margin of a small town of Southern Italy, whose reactivation of 1998 caused severe damages to some structures. To protect the upslope urban area, an anchored diaphragm wall and a drainage system were constructed in 2001. In the meantime, in order to understand the processes which caused the reactivation, a Department of the Basilicata Administrative Region provided financial support to a geotechnical investigation. Laboratory tests on undisturbed and reconstituted specimens, in situ pore pressure and deep displacement measurements were carried out. Both experimental and theoretical in situ water content (and porosity) profiles were determined. Theoretical analyses of pore pressure distribution and stability analyses were carried out. The influence of the drainage system on the slope safety factor was evaluated. Experimental and theoretical data suggest that a first time process occurred in the lower part of the landslide system. The upper part moved on pre-existing surfaces on which an average shear strength close to the residual strength was available. Noticeable water content increase was found around some of these surfaces. Erosion at the toe of the landslide was the probable cause of reactivation. The analysis of the drain system effectiveness suggests that drainage has not significantly influenced pore pressures on the considered slip surfaces yet, mainly because of the very low permeability of the clay.     

Dissipation Testing of Singapore Marine Clay by Piezocone Tests

In situ dissipation tests provide a means of evaluating the in situ coefficient of consolidation due to horizontal flow and hydraulic conductivity in horizontal direction in marine clays formation. Dissipation tests by means of piezocone were utilised in the characterisation of the coefficient of consolidation due to horizontal flow and the hydraulic conductivity in horizontal direction of Singapore marine clay at Changi. Piezocone dissipation tests were carried out prior to reclamation as well as after ground improvement with vertical drains to compare the changes in the coefficient of consolidation due to horizontal flow and hydraulic conductivity in horizontal direction prior to and after ground improvement. The quasi-static piezometric pressures from the dissipation tests were compared with piezometric pressures from piezometers to determine their possibility of future use as an alternative to piezometers. Post-improvement CPTU dissipation tests were carried out in the treated “Vertical Drain Area” as well as in an adjacent untreated “Control Area” for comparison purposes. This study provides support for the use of piezocone dissipation testing methods for the determination of the coefficient of consolidation due to horizontal flow and hydraulic conductivity in horizontal direction of marine clays in the region as well as an alternative to piezometer instrumentation for monitoring of piezometric pressure during consolidation.     

Clay soil typification by diffusion and osmotic permeability

This paper discusses an integrated approach to the diffusion and osmotic parameters of argillaceous soils based on clayey soil classification by their microstructure and mineral varieties. The paper substantiates, within this approach, typification of microstructure-mineral varieties of argillaceous soils by their diffusion and osmotic permeability, which can be utilized for applied purposes and in various simulation reconstructions for estimating the parameters of diffusion and osmotic transport.     

改性粘土增强硅橡胶性能的研究

改性粘土增强硅橡胶性能的研究魏从容吴季怀沈振（华侨大学材料物理化学研究所,泉州３６２０１１）关键词粘土矿物质表面改性硅橡胶增强剂粘土矿物作硅橡胶增强剂是粘土综合开发利用的新课题,我们在这方面取得一定的成果［１］。但是,未经改性处理的粘土其增强能力是有...     

土层锚杆模型试验研究

针对土层锚杆应力分布的复杂性,进行室内模型试验,利用所得数据,绘制了拉力型锚杆和压力型锚杆杆体全长上的应变分布曲线、同列锚杆锚固段末端点以及坡面处的应变分布曲线。在所得曲线的基础上,对坡体中锚杆的应力分布特征以及变化规律进行了分析及讨论,从而对其工作性能和加固机理进行初步研究。介绍了锚杆上剪应力分布的理论解,并将试验结果与理论分析结果进行了对比,两者基本吻合,验证了本试验结果的合理性和可靠性。     

Study of Water Flow in a Single Clay Crack

A model has been constructed to study water flow in a single clay crack, and a new concept of the critical rise rate of water level in the crack has been put forward. When the water level rises faster than this critical rate, the flow in a crack will increase, and vice versa. The flow in a crack is not in proportion to the water level. The maximium water flow in clay is 30-40 times smaller than that in a rock fissure under the same condition. In the process of water discharge, the flow in a crack will lessen gradually, and the crack will grow narrower by 3.0-4.0cm, with its depth reducing by over 50%.     

Hydrogeological modeling of radionuclide transport in low permeability media: a comparison between Boom Clay and Ypresian Clay

Deep low-permeability clay layers are considered as suitable environments for disposal of high-level radioactive waste. In Belgium, the Boom Clay is the reference host formation and the Ypresian Clay an alternative host formation for research and safety and feasibility assessment of deep disposal of nuclear waste. In this study, two hydrogeological models are built to calculate the radionuclide fluxes that would migrate from a potential repository through these two clay formations. Transport parameter heterogeneity is incorporated in the models using geostatistical co-simulations of hydraulic conductivity, diffusion coefficient and diffusion accessible porosity. The calculated radionuclide fluxes in the two clay formations are compared. The results show that in the Ypresian Clay larger differences between the fluxes through the lower and the upper clay boundary occur, larger total output radionuclide amounts are calculated and a larger effect of parameter heterogeneity on the calculated fluxes is observed, compared to the Boom Clay.     

粘土固化注浆堵水试验研究

论述了粘土（湖泥）固化注浆技术在矿山堵水中的试验研究情况，包括矿区水文地质情况，注浆浆液的配制及性能研究，制浆及注浆施工，质量检查和经济效益分析。     

粘土矿物的X射线衍射物相分析

文章总结了粘土矿物的Ｘ射线衍射物相分析经验。阐述粘土矿物的分析条件,制样方法和衍射图解释等特点。研究重系定量分析方法,总结出几种常见的粘土矿物的权重系数。讨论了放物高温衍射分析问题。     

X射线荧光光谱法测定高铝粘土中主成分方法研究

使用日本理学ZSX PrimusⅡ型X射线荧光光谱仪,采用熔融玻璃片和经验系数进行基体校正的方法,对我室6件国家标准物质、4件监控样以及用标样和纯值试剂配制的21件混合标准进行组分测定。分析结果表明,此方法能快速、准确测定高铝粘土中主成分Al2O3、SiO2、Fe2O3、TiO2,其准确度和精密度均能达到国家标准方法规定的要求。     

强夯碎石柱法处理淤泥质粘土地基

常规强夯法处理淤泥质粘土地基效果不太理想。本文论述了强夯碎石柱法的原理及应用的可行性,对夯后形成复合地基的沉降、固结,稳定性等问题用多种方法进行了计算,讨论了施工中可能出现的情况。国内外成功的实例表明该法在处理饱和软粘土地基时有着良好的应用前景。     

用改性粘土矿物治理赤潮灾害的前景

赤潮,这一当今全球性的海洋灾害,正严重干扰着３０多个沿海国家的经济发展。近年来,我国已成为一个赤潮灾害多发的国家。我国大陆沿海１９７２年至１９９４年记录有２５６次赤潮灾害,且呈逐年增加趋势。据统计,仅１９９８年的赤潮所造成的经济损失就已超过１０亿人民币。１９９８年是我国赤潮重灾年：三四月份,赤潮袭击香港,造成约３亿港元的损失。广东省从饶平市、汕尾市到深圳、珠海、阳江沿海相继发生了赤潮,蔓延速度之快,致灾面积之大,实属历史罕见,是广东省近１３年来最严重的一次,造成的经济损失超过１亿元。１９９８年下…