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1.
ZHAN Liang-tong CHEN Ping NG C.W.W. 《浙江大学学报(A卷英文版)》2007,8(5):699-706
A laboratory study was carried out on both natural and compacted specimens to investigate the complex soil-water interaction in an unsaturated expansive clay. The laboratory study includes the measurement of soil-water characteristic curves, 1D free swelling tests, measurement of swelling pressure and shrinkage tests. The test results revealed that the air-entry value of the natural specimen was quite low due to cracks and fissures present. The hydraulic hysteresis of the natural specimen was relatively insignificant as compared with the compacted specimen. Within a suction range 0 to 500 kPa, a bilinear relationship between free swelling strain (or swelling pressure) and initial soil suction was observed for both the natural and compacted specimens. As a result of over-consolidation and secondary structures such as cementation and cracks, the natural specimens exhibited significant lower swelling (or swelling pressure) than the compacted specimen. The change of matric suction exerts a more significant effect on the water phase than on the soil skeleton for this expansive clay. 相似文献
2.
为探究降雨入渗作用下排水钉的排水性能及其对土体渗流场的影响,通过开展室内试验、建立排水钉数值模型、定义流量函数模拟降雨入渗过程,分析排水钉排水量及土体中体积含水率和孔隙水压力的变化规律。 结果表明:随着降雨时间的增加,排水钉排水量不断增大直至最大值,排水量处于最大值一段时间后,土体表面积水入渗完成,排水量开始大幅减小。 随着降雨入渗的发展,各监测点处体积含水率均达到土体饱和体积含水率,各处孔隙水压力值由负变正,降雨停止后,由于排水钉的排水作用,各处体积含水率均不断减小,最终,各监测点处体积含水率均小于初始状态,孔隙水压力值由正变负。 数值模拟结果能与室内试验结果具有良好的一致性。 研究结果说明排水钉具有良好的排水效果,可有效解决工程中降水的排出问题,能够为工程的排水设计提供借鉴。 相似文献
3.
膨胀土的水分特征曲线通常是在实验室测得的, 在现场测量膨胀土的吸力不仅费时而且也非常困难. 本文采用人工神经网络技术用现场测得的含水量来预测土的吸力. 网络训练首先采用水分特征曲线相应的试验数据进行监督训练, 然后利用监督训练得到的网络单元的连接权值对现场测得含水量数据进行吸力预测, 预测结果与实测结果相近, 同时并对预测结果进行了分析讨论. 相似文献
4.
The use of loess as an earthen final cover material is promising in northwest China which has an arid and semi-arid climate. A full-scale testing facility with an area 30 m long by 20 m wide was constructed at the Xi’an landfill of municipal solid wastes to investigate the performance of an inclined capillary barrier cover. The cover consisted of a compacted loess layer underlain by a gravel layer. The testing facility was well instrumented for a gas permeation test and recording of the soil conditions in terms of volumetric water content, pore gas pressure, and soil temperature. Tests were performed to measure the gas permeability of the compacted loess before and after the planting of vegetation on the cover. The field measurements demonstrate that the capillary break at the fine/coarse soil interface allows the upper compacted loess layer to retain more water, and conversely reduces its gas permeability, which is favorable for reducing landfill gas emissions. When the degree of saturation of the compacted loess was greater than 85%, the gas permeability decreased significantly with a further increment in volumetric water content. The growth of vegetation roots tended to fill the large pores in the upper loosely-compacted loess, resulting in a decrease in gas permeability of one order of magnitude. The influence of soil clods in the compacted loess on gas permeability can be one to two orders of magnitude due to an increase in pore size and a decrease in tortuosity. 相似文献
5.
Soil liquefaction can cause disastrous consequences to buildings and human lives. Regular countermeasures against soil liquefaction are often overly expensive for normal buildings and structures. This could be the major reason that liquefaction induced damage is still widely encountered in large- and mid-size earthquakes in recent years. In this paper, a new method for the mitigation of soil liquefaction using the microbially induced soil desaturation is proposed and tested. The desaturation effect in soil is achieved by the generation of nitrogen gas produced from the microbial denitrification process. Some major issues related to this method are experimentally investigated. These include soil desaturation procedures, shapes and distribution of gas bubbles in soil, mechanical responses and liquefaction resistance of desaturated soils, and stability of gas in soils. The desaturation treatment of soils is made simply by introducing denitrifying bacteria and a desaturation solution into soil pores by mixing, flushing, or injection. The degree of saturation can be reduced as the microbial reaction proceeds. Experimental results show that the final degree of saturation is related to the initial nitrate concentration added to the soil: the higher the concentration of nitrate in the desaturation solution, the lower the degree of saturation that can be achieved. The existence of gas bubbles in soil is evidenced by computer tomography (CT) technology. The CT images reveal that gas is in the form of small pockets which has a size a little larger than the mean size of sand grains. It is shown in the shaking table tests that microbially induced desaturation can effectively improve the liquefaction resistance of soil by showing a much lower pore pressure generation, much smaller volumetric strain, and much smaller settlement of the structure in desaturated soil, as compared with those in saturated soil. Triaxial consolidated undrained tests reveal that the desaturation treatment of soil can improve the undrained shear strength of loose sand. The stability of gas is tested under hydrostatic and water flow conditions. The gas phase is stable under the hydrostatic condition, but unstable under water flow conditions. So measures ought to be taken to prevent steady flow in practice. 相似文献
6.
一种测试不同温度下非饱和土土-水特征曲线的试验装置 总被引：2，自引：0，他引：2
研究目的：研制一种试验装置,以实现对非饱和土土-水特征曲线温度效应的有效测试。创新要点：1．研制了一种温控非饱和土三轴试验装置,包括加载系统、吸力控制系统和温度控制系统;2．利用研制的温控非饱和土三轴试验装置,对不同温度（25,40和60℃）以及不同应力（40100和200kPa）条件下的非饱和土土-水特征曲线进行了试验测定。研究方法：1．总结分析已有的温控三轴仪所采用的加热方式的优缺点,提出环向加热压力室内水体的方法;2．基于GDS非饱和土三轴仪,研制可实现温度控制功能的温控非饱和土三轴仪（图1、2）;3．开展不同温度及不同应力条件下非饱和土土水特征曲线的试验研究。重要结论：1．所研制的温控非饱和土三轴仪的实用效果得到验证;2．温度的升高将引起非饱和土持水性能的降低。 相似文献
7.
The crucial point in calibrating soil water content using the technology of time domain reflectometry (TDR) is to establish the relationship between the apparent dielectric constant and the water content. Based on a database, which included 45 kinds of soil samples and 418 data points from our own test data and relevant literature, an empirical calibration equation is proposed. Additionally, the influence of soil type, dry density of soil, compaction energy, pore fluid conductivity, and temperature on the calculated result for water content was also analyzed. Results show that the equation can offer an error of ±0.05 g/g for most soils encountered in geotechnical engineering. However, the estimation error given by the empirical equation becomes significant for soils with dry density less than 1.3 g/cm3, so the equation was modified to consider the influence of dry density. Both of the empirical equations can be used to test gravimetric water content using the TDR method conveniently and efficiently without calibration. 相似文献
8.
Influences affecting the soil-water characteristic curve 总被引：2，自引：0，他引：2
INTRODUCTION The soil-water characteristic curve (SWCC) gives the relationship between the amount of water in the soil (i.e. gravimetric or volumetric water content) and soil suction (i.e. matric suction at low suction and total suction at high suction). Many properties of a partially saturated soil such as the coefficient of permeability, shear strength and volume strain, pore size distribution, the amount of water contained in the pores at any suction, can be obtained from the SWCC. … 相似文献
9.
钱塘江吹填土的沉淀特性研究 总被引：7，自引：0，他引：7
钱塘江标准塘Ⅴ期的吹填土的颗粒分析曲线和沉淀试验显示：对粉土来讲，干密度、沉积的快慢与含水量没有明显关系；级配较好的土，沉积后的干密度较大；土的自重在欠固结土中发挥着重要作用。 相似文献
10.
Bucket foundations[1 ,2]are a relatively newtype offoundation usedto support offshore structures .Each bucketfoundation consists of a thin cylindrical steel shell ,cappedwithalid of steel or concrete .Thefoundationcan penetrateinto sea floor when pumping … 相似文献
11.
采用剖面分析方法,初步研究了梅州市清凉山库区两种主要森林类型土壤物理性质及其对水源涵养功能的影响。结果表明：研究区的两种主要林分土壤物理性质差异明显,天然常绿阔叶林的土壤物理性质较好,具有良好的水源涵养功能。在两种林地中,人工按树林地表层土壤砂粒含量明显偏高,是天然常绿阔叶林地的1．59倍;黏粒含量的分布则相反。人工按树林地表层土壤容重和比重皆大于天然常绿阔叶林地,且由袁土层至心土层呈现逐渐增加的趋势。土壤孔隙度与自然含水量则天然常绿阔叶林地大于桉树林地。在土层垂直方向上,常绿阔叶林地的物理性质变化差异较大,人工桉树林地相对较小。 相似文献
12.
赵建红 《北京工业职业技术学院学报》2006,5(3):54-58,115
通过对水泥土块强度试验,分析了影响夯实水泥土桩强度的主要因素,并详细论证了水泥掺入比、土的种类、桩体干密度及养护龄期等因素与水泥土桩体强度之间的关系. 相似文献
13.
包太 《重庆大学学报(英文版)》2003,2(1)
1. Introduction At present, the construction of large-scale reservoirworks has given rise to many large-scale reservoirareas, the stabilization of slopes in these reservoirdistricts will be influenced by water waves. Thecirculating hydraulic loading caused by the waveproduces a great force on the slope, and especiallyforms a vibration wave force on the boundary of water surface and the slope earth, and even breaks the water-soil interface, leading to the excess pore pressurechanging along diff… 相似文献
14.
本文采用空气加压渗流技术制备了含宏观孔开孔泡沫铝材料。宏观孔的直径大小为0.8毫米和1.4毫米,宏观孔体积分数为69%和76%。通过多功能内耗仪采用内耗技术测试了泡沫铝在不同温度、不同频率和不同振幅下的内耗谱特征,利用内耗技术研究了宏观孔开孔泡沫铝的阻尼行为。泡沫铝的阻尼能力比致密工业纯铝的阻尼能力得到了很大的提高,泡沫铝的内耗随着测量频率的增加而增加。同时,内耗也随着应变振幅的增加而增大。运用透射电子显微镜对材料的微观结构进行了观察,发现在晶界附近存在有大量的位错亚结构。根据内耗测量和微观观察提出了泡沫铝中可能的阻尼机制：孔周围的应力集中和模式转换、孔洞/金属基体界面处由于动力学模量相差很大而使机械能转化为热能和孔洞发生不均匀的膨胀或畸变使外加应变能耗散为热能。 相似文献
15.
以陕西省志丹县顺宁镇任坪村保娃沟门流域的前拐沟黄土作为研究对象,按照土工试验规程（SL237-1999）进行分类、击实、渗透等各项试验,对试验结果进行分析。分析结果表明,该流域黄土的Cu〉5,Cc∈（1,3）,小于0.005mm的土粒含量18.95%,土料的液限ωL平均为27.98%,塑限WP平均为17.10%,塑性指数Ip平均为10.89;土样最大干密度为1.70g/cm^3,最优含水率为14.99%;渗透系数为4.32×10^-5cm/s。该区土壤粒径分布不均匀且级配良好,渗透性较好,适合筑坝工程要求。 相似文献
16.
文章对哈尔滨地区的粉质粘土进行了冻结过程的水分迁移试验,考察了含水率、冻结温度及干密度在封闭系统的条件下对粉质粘土中水分迁移的影响。结果表明,控制含水率和干密度相同,顶板的冻结温度越高,水分迁移量越大,顶板冻结温度为-3℃的水分迁移量较冻结温度为-9℃的水分迁移量大;控制顶板冻结温度和干密度相同,初始含水率大的试样,水分迁移量大;控制顶板冻结温度和含水率相同,水分迁移量随干密度的增加而减小。 相似文献
17.
土壤水分调控对冬小麦水分利用特性及产量的影响 总被引：2，自引：0，他引：2
综述了土壤水分对冬小麦水分利用特性及产量的影响.我国麦区时常出现干旱,由于土壤水分缺少而使根系吸水区域向下扩展,提高了土壤水分的利用率;同时,土壤水分缺少也影响了器官生长,使叶面积减小,群体叶片光合性能下降,土壤水分缺少也使开花后的光合产物减少,灌浆物质不足,从而造成减产. 相似文献
18.
Based on effective media theory, a predictive model, relating chloride diffusivity to the capillary pores, gel pores, tortuosity
factor, and pore size distribution of hardened cement, is proposed. To verify the proposed model, the diffusion coefficient
of chloride ions, the degree of hydration, and peak radius of capillary pores of cement paste specimens were measured. The
predicted results for chloride diffusivity were compared with published data. The results showed that the predicted chloride
diffusivity of hardened cement paste was in good agreement with the experimental results. The effect of the evolution of pore
structures in cement paste on chloride diffusivity could be deduced simultaneously using the proposed model. 相似文献
19.
盐渍土水分下渗能力及水盐动态运移试验 总被引：1，自引：0，他引：1
为探究盐渍化土壤水分下渗规律、水分下渗能力及水盐动态运移过程,设计了土壤剖面分层定水头供水及土壤剖面变水头供水下渗实验。测定不同层位土壤水分下渗率、含水率、孔隙水溶液电导率及土壤体电导率等参数,进行入渗条件下水盐动态运移规律分析。试验结果表明:盐渍化土水分下渗规律可由积水入渗Kostiakov模型进行刻画;浅层0~40 cm土壤相对于深层40~60 cm土壤具有较强的拦截和贮存入渗水分能力;盐渍化土壤盐分变动带位于浅层0~40 cm,且20~40 cm深度的土壤盐分波动幅度较大,深层40~60 cm土壤孔隙水溶液盐分向下运移的通量与土壤体盐分对其的补充量达到动态平衡,水分下渗过程中深层土壤孔隙水盐分含量相对平稳。实验结果为盐渍土的防治提供参考。 相似文献