共查询到19条相似文献，搜索用时 140 毫秒
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为探究阶地饱和砂质粉土在黄土滑坡冲击荷载作用下的力学机理，选取泾阳南塬典型黄土滑坡LD37为研究对象。通过基本性质测试获取了阶地砂质粉土的物理、水理、颗粒级配和矿物组分等指标。采用自制冲击设备进行了3种饱和度条件下的冲击试验，并对水分迁移和剪切强度变化等问题进行了分析，在此基础上探讨了冲击液化机理。结果表明:冲击荷载会使砂质粉土内部的总应力与孔隙水压力剧增，在应力波的作用下，出现多个峰值，且孔隙水压力在1 s内难以完全消散；80%与90%饱和度的砂质粉土受冲击会在深度方向上形成不同程度的液化，而70%饱和度的砂质粉土受冲击后沿深度方向并未发生液化；砂质粉土发生冲击液化时下部水分会向上部迁移，导致其上部土层含水率骤增，剪切强度骤减；冲击液化过程可划分为初始阶段、冲击挤压阶段和冲击回弹阶段。砂质粉土的冲击液化机理是一种由于快速冲压土体的不排水行为，导致其颗粒原始骨架结构破坏重组，从而引起其内部孔压快速积累的一种液化行为。 相似文献
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给水度是重要的水文地质参数之一,为探讨潜水含水层给水度的影响因素,设计均质粗砂、均质细砂、上细下粗、上粗下细4种土柱的排水实验,按照一定间距分段降低地下水位,每段降深设计不同排水时间,求取不同水位埋深的给水度.当地下水位埋深小于支持毛细水高度,给水度受地下水位埋深影响显著,其关系可以用非线性函数来表示.排水时间越长,给水度越大,当土柱分段排水时间超过1 h,给水度值稳定.0.6~0.9 mm粒径的粗砂给水度大于0.2~0.4 mm的细砂;当地下水位在土层分界面下20 cm时,上细下粗土柱给水度显著增大,上粗下细土柱给水度显著减小.给水度的大小与地下水位埋深、排水时间、岩土颗粒和潜水面附近及之上非均质结构等因素有关. 相似文献
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包气带水分入渗过程受多种因素的影响。定量研究层状非均质岩性结构和入渗速率对其影响,有助于解决根据不同条件选择单相流模型或水气二相流模型模拟包气带水分入渗过程的问题。结合填埋场等场地地层条件及污废水入渗特征,分别建立了“上细下粗”和“上粗下细”包气带层状非均质岩性结构水分入渗单相流和水气二相流模型,探讨不同层状非均质岩性结构条件下模型的适用性。在“上粗下细”岩性结构模型基础上,进一步探究入渗速率对水气两相运移结果的影响。基于论文模型研究表明:（1）在包气带岩性结构为“上细下粗”的条件下,气相的影响基本可以忽略,可直接采用单相流模型对包气带水分运移进行模拟;在“上粗下细”岩性结构和本次模型设定的底部压力保持不变及污废水泄漏前场地未接受降水入渗补给等条件下,当包气带上下层介质渗透率比值大于16倍时,气相会对水相运移产生明显影响,且下层介质渗透率越小、上下层介质渗透率比值越大,单相流与两相流的运移结果差别越大,需要采用水气二相流模型模拟包气带水分运移。（2）在包气带“上粗下细”岩性结构条件下,入渗速率越大,气相对水流入渗的阻滞作用越明显,此时包气带水分运移模拟应采用水气二相流模型。 相似文献
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为了揭示路基冻结过程中地下水和土性对水分迁移规律的影响,针对开放体系和封闭体系的粉质黏土和砂土进行了单向冻结条件下的水分迁移试验。通过土柱上层位置设置碎石层,阻断液态水迁移路径,监测冻结过程中土柱的水热变化,结合土柱冻结深度、冻结速率曲线、含水率分布曲线和补水时程曲线,分析仅水汽补给时对土柱顶部水分聚集和冻结特征的影响。试验结果发现,无论是封闭体系还是开放体系,粉质黏土和砂土土柱都会在冻结区中形成两处水分聚集区:第一水分聚集区为控温板底部,以霜的形式聚集,主要是由土柱顶部土体的水汽迁移并凝华相变形成;第二水分聚集区为冻结区中液态水和气态水共同迁移形成,随着冻结锋面的向下推移,形成不连通孔隙的界面,液态水向0℃冰锋线迁移聚集并相变成冰,水汽迁移路径受阻而凝华成冰,致使该处含水率显著增加。相较于封闭体系,开放体系使两处水分聚集区产生更大的水分增量。相比于粉质黏土,砂土介质孔隙较大,在试验时间内水汽补给对水分聚集区的影响更明显,但由于砂土持水能力减弱,水汽补给速率随时间逐渐减小。 相似文献
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针对封闭系统下粗颗粒硫酸盐渍土在冻结过程中的水盐迁移和变形特性开展了理论和试验研究。基于非饱和多孔介质热弹性理论,考虑孔隙水盐相变,建立了适用于粗颗粒盐渍土水-热-盐-力多场耦合模型,并对单向冻结条件下粗颗粒盐渍土的温度场、水分场、盐分场和位移场分布进行了数值模拟。通过配制含硫酸盐的细砂作为土样开展了单向冻结条件下的室内试验,测定了冻结过程中的温度、水分、盐分以及变形的分布,并与数值结果进行了比较,验证了理论模型的有效性。结果表明:砂土结构孔隙更大,水分和盐分更容易渗透和迁移,在单向冻结试验中,水盐迁移速度更快;细砂的轴向位移呈现先下降后上升的变化趋势,且收缩变形持续时间较黏土更长;由于暖端水分向冷端迁移致使暖端土体孔隙减小,下部土体变得更加密实,土柱下部侧壁压力大于上部。 相似文献
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受界面效应影响,毛细水在层状土中运移规律还难以用描述均质土中水分运移规律的Lucas-Washburn（LW）渗吸模型进行描述。基于此,本文设计了层状土室内模型试验,采用分布式的主动加热光纤法（简称AHFO）监测毛细水上升过程。根据AHFO测试结果,进一步对LW模型进行了修正,提出了适用于描述层状土中毛细水上升规律的ILW模型,并对ILW模型进行了试验验证。试验结果表明:（1）当毛细水湿润锋抵达“黏土（下部）-砂土（上部）”界面时,会产生“毛细屏障作用”,从而导致上部砂土中毛细水含水率急剧下降;（2）“毛细屏障作用”由砂土和黏土中的基质吸力不均衡造成,基质吸力大小由含水率决定;（3）当毛细水湿润锋抵达“砂土（下部）-黏土（上部）”界面时,在界面处出现“反毛细屏障作用”,从而导致上部黏土层中的含水率比相邻下部砂土层含水率更高;（4）虽然常见的LW模型可准确预测均质土中毛细水上升高度及速率,但受“毛细屏障作用”和“反毛细屏障作用”影响,LW模型在层状土中失效;（5）相比LW模型,ILW模型精度更高,能够更加准确地描述层状土中毛细水上升规律。 相似文献
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不同地区饱和原状黄土静态液化特性试验研究 总被引：1，自引：0，他引：1
黄土因饱水静态液化而发生突发性失稳破坏,易造成人员伤亡和财产损失。按照颗粒级配的不同,中国黄土分为砂质、粉质和黏质黄土,不同区域的黄土具有不同的静态液化特性。利用GDS三轴试验系统,对陕西神木砂质黄土区(Q_3黄土)、甘肃黑方台粉质黄土区(Q_3黄土)和陕西泾阳黏质黄土区(Q_2黄土)原状饱和黄土进行了等向固结不排水三轴剪切(ICU)试验,研究了初始孔隙比和颗粒级配对原状黄土静态液化能力的影响。试验结果表明:①3个地区的饱和原状土的应力-应变关系均为软化型,在中低围压下泾阳饱和原状黄土不发生液化,仅表现出弱软化现象;②中低围压下,初始孔隙比是影响原状黄土静态液化的主要因素,高围压下,初始孔隙比的影响逐渐减小,颗粒级配成为影响原状黄土静态液化的主要因素。 相似文献
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在冻融循环环境下,路基结构内水分迁移是导致道路冻胀、融沉变形的主要原因。为了探究冻融循环条件下路基结构的水热汽迁移规律,模拟了实际工程的路基结构,基于半透膜材料开展了冻融循环条件下的水、汽分离的水分迁移试验,通过监测试样的水热变化、荧光素上升图像、补水量和集水量变化曲线,得到了水分迁移规律,进而分析了土的孔隙结构、升降温速率和温度梯度等因素对水汽迁移和液态水流出特征的影响。试验结果表明,在土水势作用下,马氏瓶的水分首先以水-汽混合的形式在土柱中向上迁移,达到一定高度后,转变为以水汽的形式向上迁移。非饱和土柱的水汽会透过半透膜向碎石层和控温板底迁移,在整个冻融循环过程中,水汽向碎石层和控温板底的迁移量呈现线性增加的趋势,表明水汽迁移在水分聚集过程中的作用不可忽视。碎石层和控温板底液态水的流出主要集中在每个冻融周期的两个阶段,第一阶段为降温阶段,以冷凝水为主;第二阶段为融化阶段,以融化水为主,融化水占一个冻融周期液态水流出量的70%以上。粉质黏土孔隙较小导致水汽迁移主要受体积含气率的影响,随着粉质黏土土柱含水率的增加,水汽迁移量呈减小趋势。而砂土的孔隙较大,水汽迁移主要受水汽扩散增强因子的... 相似文献
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Temperature changing in soil has an influence on the redistribution of water and salt. With constant temperature in an open
system we performed two unidirectional freezing tests with different temperature settings of clay collected at Beiluhe test
site along Qinghai–Tibet Railway. The groundwater supply of the soil was simulated during the experiments by attaching a liquid
replenishment system to the bottom of the sample container. Water content and ions content of the soil were measured after
the experiments. By analyzing the two main ions in the soil we obtained the laws and the properties of water and salt redistribution
during freezing of clay soil. The results show that the water content increases in freezing section while it decreases in
unfrozen section compared with initial water content. To the salt, under this circumstance the diffusion due to the concentration
gradient dominated the transfer way in clay soil, so the ions content in the unfreezing section decreased with the decreasing
of the distance to freezing front. At the ice segregation layer the ions content is less due to the ice self-purification,
and almost nothing changed in frozen section. 相似文献
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基于冻融交界面直剪试验的冻土斜坡失稳过程研究 总被引：1，自引：0，他引：1
为了探讨多年冻土区自然斜坡失稳机制,开展了不同含水率黏土、粉土、砂土的土-冰交界面直接剪切试验和相应融土的直接剪切试验。结果表明,砂土和砂土-冰冻融交界面剪切应力-变形特性主要表现为弹性变形,且剪应力存在明显峰值;粉土、黏土及相应的冻融交界面在很小的变形范围内表现为塑性变形,且剪应力无峰值。水分对砂土活动层抗剪强度影响较弱,表现为水分增高,内摩擦角小幅降低。水分对粉黏土活动层抗剪强度影响剧烈,表现为水分增高,粉黏土黏聚力急剧减小。研究发现,冻土区斜坡失稳更易发生于细颗粒粉黏土中。相对于粉土,粉土-冰冻融交界面抵抗剪切变形的能力更强,粉土斜坡潜在滑动面更易发育在冻融交界面上层附近;相对于黏土,黏土-冰冻融交界面抵抗剪切变形的能力更弱,黏土斜坡更易在冻融交界面处发生滑动。同时,细粒土斜坡极易在达到最大融化深度前提前失稳,斜坡坡度越高,失稳时间越提前。融化期活动层水分增多导致潜在滑动面黏聚力降低是细粒土冻土斜坡失稳的最主要原因,孔隙水压对冻土斜坡具有一定影响,在稳定性评价时要考虑活动层水位的影响。 相似文献
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In this paper, the plexiglass experimental column was used to analyze the capillary fringe thickness of three kinds of lithologies-silty sand, silt and silty clay-providing a basis for defining the interface in the study of hydrodynamics at the water table between vandose water and groundwater. The capillary fringe generally refers to the subsurface layer in which the groundwater seeps up to the air-entry suction value due to capillary action, and is nearly saturated with water. The thickness of the capillary fringe varies with different lithologies. In this experiment, self-made stable water supply devices were used to study the height of capillary rise, capillary water volume and capillary fringe thickness of the three lithologies through capillary experiment and numerical simulation. Experimental results show as follows:(1) Rising height of capillary water is related to time, particle radius, volume, etc., and the relationship between height and time is in line with the Hill model.(2) The smaller the particle radius, the more water the pores contain, and the ratio of the unsaturated portion of capillary water to the total water content gradually rises. Experimental results obtained by numerical simulation, segmentation and actual measurement are consistent.(3) The thickness of the capillary zone is related to the lithology. The larger the particle size, the smaller the thickness of the capillary fringe, and vice versa. In silty sand, the thickness measures about 13 cm. The figure rises to 16 cm in silt, and 37 cm in silty clay. This work studies the law of soil water transport at saturated-unsaturated interface. Experimental results are of great significance to the study of soil water and salt transport and soil salinization control in unsaturated zone. 相似文献
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土壤水盐分布严重影响煤矿区排土场生态重建及植物组配模式,为探究菌根植物影响下煤矿区排土场“表土层-含水层-隔水层”三层重构模式下的土壤水盐分布特征,采用室内土柱试验,设置种植玉米+接种丛枝菌根真菌(YM+AMF)、仅种植玉米(YM)和不种玉米+不接菌(CK)3个处理。结果表明：(1)不同处理对土柱底部水分运移特征无显著影响,各处理含水层毛细水上升高度均约为10 cm;(2)水分与盐分分布随土层深度均呈正相关关系;接种AMF有利于保持表层土壤水分含量,相较于YM处理土壤含水率在0～10、10～20 cm分别提高52.0%、43.9%;接菌处理降低了10～50 cm土层的盐分含量,在20～30、30～40、40～50 cm处接菌处理的电导率较YM处理分别低了41.0%、14.1%、8.1%;(3)利用MixSIAR模型量化了不同深度土层水分对玉米的贡献率,表明YM和YM+AMF处理的主要供水层皆位于0～10 cm,供水率分别为44.3%和30.5%。同时,在累计土壤剖面水分贡献率上,接菌显著提高了中深部土层(20～70 cm)的水分贡献率,累计提升了13.8%。该研究成果对西部矿区“以水量... 相似文献
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层状土壤上升毛管水运移特性试验研究 总被引：3，自引：0，他引：3
通过室内土柱模拟试验,进行了层状土与均质土的对比试验,对层状土壤毛管水运动特性进行了研究,分析了层状土壤毛管水上升高度、速率及地下水补给量与时间的关系,并研究了毛管水上升高度与地下水补给量之间的关系。结果表明,砂层对毛管水上升的高度、速率以及地下水补给量有明显影响,砂层对于水分有着明显的阻滞作用。 相似文献
16.
细粒含量对粉土动孔压发展模式影响的试验研究 总被引：2，自引：1，他引：1
采用多功能静动液压剪切仪进行了粉土动荷载下的孔压试验,探讨了黏粒含量和粉粒含量对重塑粉土动孔压发展的影响。试验模拟大震时细粒含量影响的孔压发展规律,对已有的指数形式孔压模式进行修正,以便模拟初始液化发生后达到一定液化程度的实际情况,该模式包含2个参数a和b。研究结果表明,细粒含量对粉土动孔压发展影响较大,其影响主要体现在孔压发展模式参数b上。粉土中粉粒含量与孔压参数b的关系呈单调的线性关系,而黏粒含量与孔压参数b的关系则不是单调的线性关系,是在黏粒含量为8 %时孔压参数b达到的最大值,试验数据验证该修正的动孔压模式有更广泛的应用性。 相似文献
17.
Dynamics of the soil water and solute in the sodic saline soil in the Songnen Plain,China 总被引：2，自引：2，他引：0
According to the field experiment in the sodic saline soil region in the Songnen Plain, the dynamics of the soil water and
solute affected by the shallow groundwater were explored during the growing season in 2004. The results presented that, influenced
by the strongly evaporative demand, the soil water tended to transport to the upper soil layer with salt. The layered soil
water balance model (LSWB model) revealed that the ratio of the water exchange between the groundwater and upper layer of
the soil was 11.7:1. The groundwater discharge was 53.86 mm, but the groundwater recharge from the upper layer of soil was
only 5.04 mm from 11 July to 06 September, which indicated that the groundwater could discharge to upper layer of soil and
influence the soil salinization through capillary rise. The observed values of the salt content from July to mid-October presented
that the soil solute was more changeable influenced by the climatic condition at 30 cm depth. As the field saturated hydraulic
conductivity was low, the salts mainly accumulated in about 50–70 cm depth soil layer and hardly leached into deeper soil
layer. Furthermore, the salt content was mainly controlled by the groundwater in the subsoil below 100 cm depth, the salt
content decreased with the groundwater level receding. As influenced by the shallow groundwater and freeze-thaw action, further
studies should be performed on the mechanism of soil salinization in the sodic saline soil region in the Songnen Plain of
China. 相似文献
18.
在现场调查和钻探的基础上,采集了沐官岛水库库区3种典型底质(粉质粘土、泥质粉沙和中细砂)的原状/扰动土样和地表水样,然后分别采用静水土柱和动水水槽试验测定盐分的时-空变化规律,最后定量计算出不同底质盐分的释放通量,从而为该海湾水库蓄水初期水质的评价和预测提供了科学依据.土柱试验表明,在分子扩散作用下高盐分区主要集中在水-沉积物界面之上7.5 cm的范围内,7.5 cm之上的水体盐分较为均一,底质盐分释放通量按粉质粘土、中细砂、泥质粉沙的顺序递减,盐分释放通量符合负的幂指数形式,而且抽排界面之上高浓度水体对降低水体盐分含量效果显著.根据水槽模拟试验,风的吹拂会影响到界面之上水体盐分的分层,有利于海湾水库中盐分的混合作用. 相似文献
19.
The existence of thick compressible varved clayey silt deposits along the Delaware River presents one major obstacle for design and construction of structures or industrial facilities in this region. To understand the characteristics of this thick weak soil layer and then develop reliable soil parameters for future earthwork design and construction, a comprehensive soil testing program was carried out. The program consisted of both in situ tests [e.g., standard penetration test borings, piezocone penetration test (CPT) soundings, Marchetti flat dilatometer test soundings, seismic shear wave test soundings, CPT pore pressure dissipation tests, and field vane shear tests] and laboratory tests (e.g., soil index tests, consolidation tests, triaxial tests, and chemical tests). Additionally, a field surcharge test program with and without installation of wick drains was carried out to investigate the compressibility of the thick clayey silt deposit and the efficiency of wick drains to help accelerate consolidation. The field and laboratory test results showed that the varved clayey silt deposit was normally consolidated to slightly overconsolidated and moderately to highly compressible. Its physical properties were intermediate between those of Savannah muddy clay and Shanghai soft clay, while much closer to that of Shanghai soft clay. Due to its lamination structure in the horizontal direction, the horizontal consolidation coefficient of the varved clayey silts was significantly greater than that in the vertical direction. The measured undrained shear strength of the varved clay silt almost increased linearly with depth. The installation of wick drains in the thick clayey silt deposits accelerated primary consolidation, but showed no effect on the secondary consolidation under constant loading. The findings obtained from this study will be beneficial for future design and construction of earthworks along the Delaware River. 相似文献