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1.
泥石流源区弱固结砾石土的渗透规律 总被引：7，自引：5，他引：7
泥石流源区砾石土的渗透过程是泥石流形成全过程中不可缺少的一个子过程，该研究对泥石流形成规律的认识和对泥石流汇流计算具有重要的意义。为此，笔者与日本学者一道选择蒋家沟支沟——大凹子沟的弱固结坡积物坡面做径流产流实验，实验区面积4000cm^2，实验用可控的头降雨，通过接收和量取超渗产流的量，判断土体是否达到稳定下渗，得出初始下渗率为0．55mm／min，参数口为0．56。通过下渗率与时间关系的曲线描述．建立泥石流源区砾石土的渗透方程，该方程可用物分析泥石流源区激发雨量过程的渗透规律，同时揭示泥石流源区产流过程地表径流的形成机理及其与流体能产生及流量的关系。通过大凹子沟1994-06-15-16日的降雨资料可计算出超渗产流为0．415mm／min．其总流量占泥石流总流量的17．8％。 相似文献
3.
饱和砂土动力液化到渗流液化过程探讨 总被引：2，自引：0，他引：2
根据饱和砂土地层地震液化现象及饱和砂土动力学试验所观察到的现象，本文从砂粒－孔隙水两相介质相互作用的角度出发，研究饱和砂土在振动荷载作用下的液化过程和机制。研究结果表明，饱和砂土受振，砂粒相对滑动并重新排列，孔隙率降低，孔隙水受压产生超静孔水压力并不断增大，部分孔隙水挤出渗流，隙水渗流对砂粒产生渗流压力。渗流压力与超静孔隙水压力迭加，形成的上托力等于或大于砂粒水中重力时，砂粒在隙水中处于悬浮状态。此时，饱和砂土宏观上表现为液态。为此，根据下沉砂粒与向上渗流孔隙水之间相对运动过程中的动力作用特征，建立了描述饱和砂土液化过程的模型和液化判据。 相似文献
4.
天津地区典型土壤剖面饱和烃分布特征 及环境意义 总被引：2，自引：0，他引：2
分析了天津地区不同环境功能区7 条土壤剖面中饱和烃含量、组成及部分地球化学参数 的变化规律, 比较了不同土壤剖面饱和烃在纵向上的变化特征。结果表明, 市区( 南开区) 及近郊 区( 武清区, 北辰区和宁河县交界处) 表层土饱和烃含量最高, 其他剖面含量较低; 随深度增大, 饱 和烃含量均有所降低, 但不同剖面变化幅度不同, 表层含量较高的剖面随深度增大, 饱和烃含量 降低幅度较大, 反之则较小。根据部分典型地球化学参数的纵向变化特征, 推测表层土壤饱和烃 主要为石油源和植物源的混合源, 且市区和郊区主要受石油源控制。不同土壤剖面表层土污染源 存在差别。同一剖面表层土壤( <30cm) 不同层次的样品的饱和烃污染源较为接近; 剖面深部( > 30cm) 不同层次样品中正构烷烃不同于表层, 且成因复杂, 既受来源于土壤中有机质降解产物的 影响, 又受表层土中饱和烃纵向迁移作用的影响。对于甾、萜类化合物, 表层土壤中饱和烃含量较 高的剖面, 深层土壤受表层土壤甾、萜类污染物迁移作用的影响; 表层土壤中饱和烃含量较低的 剖面, 深层土壤受表层土壤甾、萜类污染物影响较小。 相似文献
5.
《西部资源》2016,(4)
西藏阿里结则茶卡湖西的5个地块中,地层为第四系全新统湖积(Q4l)、冲洪积(Q4al+pl)、上更新统湖积(Q3l)。粘性土层在其中4个地块的大部分范围有分布,而在2#干湖仅呈局部分布,在1#干湖分布面积为2.11km2,在3#干湖为4.17km2,在4#河滩为2.40km2,在5#湖滩为14.40km2。各地块粘性土分布面积与各地块面积之比分别为:1#干湖76.7%、3#干湖83.4%、4#河滩71.9%、5#湖滩72.0%。颗粒分析试验可知,土样中粒径小于0.075的颗粒质量占总质量的91.9﹪~98.3﹪,粘粒(0.005)含量为25.8﹪~31.1﹪,粉粒以上粒组仅有细砂粒,含量仅占1.7﹪~8.1﹪。研究区各地块粘性土的渗透系数K在8.14×10-8~3.52×10-7cm/s之间,可确定粘性土属于极微透水层。其赋存状态和渗透特性表明,粘性土层可选作泥田防渗隔水层。 相似文献
6.
标准贯入试验是一种工程地质勘察的原位测试方法,主要适用于粉土、一般粘性土和砂土。本文首先对标准贯入试验原理进行介绍,然后对标准贯入试验的影响因素进行分析,并结合实例,对标准贯入试验在岩土勘察中的应用要点进行详细探究,以期为类似工程提供参考。 相似文献
7.
《山地学报》2017,(2)
宽级配弱固结土体中细颗粒的迁移是导致滑坡和泥石流的一个重要原因。本文总结了宽级配弱固结土和细颗粒分界粒径的基本概念,以及细颗粒迁移特性,并总结了现有细颗粒迁移在各学科研究的实验方法、数值模拟方法以及研究成果。现有研究表明在宏观尺度上,宽级配土体内细颗粒在水动力条件下的迁移,会导致土体孔隙堵塞,是土体渗透性的降低、发生滑坡泥石流的重要原因;同时亦影响水利科学中土石坝运行,甚至造成管涌破坏。在细观尺度上,相关成果仍旧不完善,亟待在今后进行深入研究。未来建议重点发展微观数值模拟技术,高精度的试验监测手段,并考虑孔隙结构和颗粒级配变化、细观-微观-宏观多尺度转换以及气、固、流多相流耦合条件下的细颗粒迁移规律。 相似文献
8.
《山地学报》2015,(3)
降雨过程中,堆积碎石土渗透特性改变是触发滑坡等灾害的主要因素。碎石土中封闭气泡阻碍水相流动,从而对雨水入渗产生影响。通过自制渗流沉降综合测试仪,进行入渗试验,探究不同雨强(1.2 mm/min、1.6mm/min、2.0 mm/min)下,碎石土的渗透规律与沉降变形。通过Seep/w软件耦合Air/w软件进一步分析不同雨强下气阻作用对湿润锋迁移速度的影响。结果表明:入渗深度-时间曲线存在阶梯状趋势,即湿润锋迁移速度首先随表层土含水率的突增迅速增加至最大值(约30~40 mm/min),然后随气压的增加缓慢减小,最后湿润锋迁移速度随气压减小略微增大,湿润锋平均迁移速率(无积水状态)随雨强的增大趋近线性增长;碎石土沉降变形在入渗过程中经历缓慢增长、急剧增大、逐渐停滞三个阶段,雨强为2.0 mm/min时,碎石土发生急剧沉降变形时间最早(约50 min);碎石土渗透系数与干密度呈线性负相关关系。 相似文献
9.
本文论述了北威尔士北美云杉林〔Ｐｉｃｅａｓｉｔｃｈｅｎｓｉｓ（Ｂｏｎｇ）Ｃａｒｒ〕土壤非饱和水在土壤剖面上的垂直和水平方向的时空变化过程及规律。结果表明，表层至１０ｃｍ深和３５～５０ｃｍ深的土壤层内非饱和水含量始终高于１０～２０ｃｍ和２０～３５ｃｍ深两层的非饱和水含量。土壤非饱和水有从上向下和从下向上补给中间层的规律。受水势梯度的影响，犁沟内非饱和水可以侧向补给相邻畦埂的土壤。在监测期，土壤中没有饱和水和过饱和水运动过程出现 相似文献
10.
本文从水岩化学作用、水土化学作用和斜坡水文化学三个方面阐述了水—岩(土)体化学作用对斜坡稳定性影响的研究历史和研究现状。分析了当前研究取得的成果及其存在的问题,从探索水—岩(土)化学作用本质规律的角度,提出应加强水—岩(土)化学反应原位监测试验、水—土化学作用损伤定量模型、水—土化学作用下抗剪强度参数变化机制的研究等。考虑到水岩化学作用与岩石风化现象的紧密关系,提出应加强岩石抗风化研究,降低地质灾害发生频率。 相似文献
11.
Lagoon berms in western Alaska are difficult to design and build due to limited resources, high cost of construction and materials, and warm permafrost conditions. This paper explores methods to treat locally available frozen materials and use them for berm construction. The goal is to find an optimized mix ratio for cement and additives that can be effective in increasing the strength and decreasing the thaw settlement of an ice-rich frozen silty soil. Soil of similar type and ice content to the permafrost found at a project site in Eek, Alaska is prepared in a cold room. The frozen soil is pulverized and cement, additives and fibers are added to the samples for enhancing shear strength and controlling thaw settlement. Thaw settlement and direct shear testsare performed to assess strength and settlement characteristics. This paper presents a sample preparation method, data from thaw settlement and direct shear tests, and analyses of the test results and preliminary conclusions. 相似文献
12.
塔克拉玛干沙漠腹地风沙土的力学性质 总被引：9，自引：5，他引：4
风沙土是形成于干旱、半干旱区的一种特殊性质的土,其力学性质不同于一般土体,结构松散性为其最主要的特点。通过对塔克拉玛干沙漠腹地14个风沙土样进行压缩试验和抗剪试验,获得了风沙土的基本力学参数:风沙土压缩模量值在50.00~142.86MPa之间,是一种低压缩性土;风沙土的内摩擦角值在31°55'~36°19'之间,低于河流冲积砂的内摩擦角值;风沙土存在结构力,其力学效应相当于粘聚力,可以在剪切试验中测出,其值在0.6~9.3kPa之间。并分析了影响这些力学参数的主要因素。 相似文献
13.
A series of tests were conducted to analyze temperature field distribution and thawing settlement of a thawing soil under static and dynamic loading at various cooling and thawing temperatures. The res... 相似文献
14.
Bank and near-bank processes in an incised channel 总被引：5，自引：0，他引：5
Gravitational forces acting on in situ bank material act in concert with hydraulic forces at the bank toe to determine rates of bank erosion. The interaction of these forces control streambank mechanics. Hydraulic forces exerted by flowing water on in situ bank-toe material and failed cohesive material at the bank toe are often sufficient to entrain materials at relatively frequent flows and to maintain steep lower-bank profiles. Seepage forces exerted on in situ bank material by groundwater, downward infiltration of rainwater and lateral seepage of streamflow into and out of the bank are critical in determining bank strength. Data from a study site on Goodwin Creek, MS, USA clearly show the temporal variability of seepage forces and the lag time inherent in reductions in shear strength due to losses of matric suction and generation of positive pore-water pressures. Negative pore-water pressures (matric suction) have also been shown to increase the resistance of failed cohesive blocks to entrainment by fluid shear. A stable bank can be transformed into an unstable bank during periods of prolonged rainfall through:
- 1. increase in soil bulk unit (specific) weight,
- 2. decrease or complete loss of matric suction, and, therefore, apparent cohesion,
- 3. generation of positive pore-water pressures, and, therefore, reduction or loss of frictional strength,
- 4. entrainment of in situ and failed material at the bank toe, and
- 5. loss of confining pressure during recession of stormflow hydrographs.
15.
In order to determine the changing rule of long-term frozen soil strength and elucidate the connection between long-term strength and soil physical properties,frozen loess was subjected to 4,6,8,10,and 50 freeze-thaw cycles,under closed-state conditions in a constant-temperature box.The frozen samples were tested on a spherical template indenter,and the results show that under the effect of repeated freeze-thaw cycles,the long-term strength of frozen loess decreased; changes in the mechanical property indices were highly unstable during the first 10 cycles; the soil strength and density were the greatest at the eighth cycle while the void ratio was the smallest; and after eight cycles all of the indices had less fluctuation and certain rising or falling tendencies.By converting the number of freeze-thaw cycles into elapsed time in the tests,three different forecasting methods of long-term soil strength could be assessed and the soil equivalent cohesive force after 10 years,20 years,or 30 years could be estimated. 相似文献
16.
通过野外现场调查、载荷试验、轻型圆锥动力触探及室内试验,对呼伦贝尔沙质草原厚度30 cm的表层沙土物理力学性质及承载力、剪切变形特征进行研究。结果表明:表层沙土工程分类为细砂,颗粒级配不良,沿深度有明显分层;干密度1.34～1.51 g·cm-3,黏聚力12～27.4 kPa,内摩擦角22.5°～24.0°,变形模量8.5 MPa;各指标表明沙土的工程性质上部差于下部;沙土承载力特征值和极限承载力分别为150 kPa和300 kPa,承载力不足导致表层沙土发生冲剪破坏(塑性破坏)和整体剪切破坏(脆性破坏)。 相似文献
17.
《Geomorphology》2006,73(1-2):115-130
Field observations and theoretical analysis have been used in the literature to assess slope instability caused by permeability variations. This investigation aims to study the influence of permeability variations on slope behaviour by experimental means. It focuses particularly on the pore water pressure generation in the vicinity of soils with different permeabilities, and the corresponding failure mode. A series of generated failures in a model with 2 soil layers was performed by means of a flume device. The soil layers were made of a medium-sized sand and a fine sand, placed in horizontal layers. A combination of photography and pore water pressure measurements was used to examine the relationship between the pore water pressure generation and failure modes. Experiments were conducted for different arrangements of soil layers (by changing the soil layer position), and infiltration direction (downward infiltration by sprinkling water on the soil, and upward infiltration from the bottom of the lower soil layer).The results revealed no clear link between the failure mode and recorded pore water pressure. Instead, the failure mode was seen to depend mostly on the relative layer position, and the recorded pore water pressures on the imposed infiltration direction. Failure was not confined to a single failure mode, but ranged instead from retrogressive slides and lateral spreads to seepage erosion. Regarding the hydrologic response, interesting results were recorded for experiments performed by downward infiltration, where perched water tables were formed. The granular nature of both soils and the absence of an impermeable barrier at the downslope end of the model seem to have favoured water seepage as the controlling failure mechanism, enhancing seepage erosion and sliding, and restricting other failure modes that require a high soil saturation such as flow failure.As the drainage conditions were not controlled, these experiments provided a unique opportunity to study the effect of water seepage as a trigger. In some experiments, failure evolution was seen to be dominated by sand washout, which started after the pore water pressure reached its maximum, suggesting that the dragging effect of seepage forces have a minor impact on triggering failure. An extra set of experiments conducted in a triaxial apparatus supported the efficacy of pore water pressure as a trigger rather than the dragging effect of seepage forces. The results obtained here provide an insight into the pre-failure mechanisms and processes of heterogeneous natural slopes. 相似文献
18.
Theoretical expressions for soil particle detachment rate due to saltation bombardment in wind erosion 总被引：1，自引：0，他引：1
Saltation bombardment is a dominate dust emission mechanism in wind erosion. For loose surfaces, splash entrainment has been well understood theoretically. However, the mass loss predictions of cohesive soils are generally empirical in most wind erosion models. In this study, the soil particle detachment of a bare, smooth, dry, and uncrusted soil surface caused by saltation bombardment is modeled by means of classical mechanics. It is shown that detachment rate can be analytically expressed in terms of the kinetic energy or mass flux of saltating grains and several common mechanical parameters of soils, including Poisson's ratio, Young's modulus, cohesion and friction angle. The novel expressions can describe dust emission rate from cohesive surfaces and are helpful to quantify the anti-erodibility of soil. It is proposed that the mechanical properties of soils should be appropriately included in physically-based wind erosion models. 相似文献
19.
There are numerous methods to prevent seepage flow and ground improvement methodologies such as cement grouting, sheet piling, and the membrane method. In this paper, we present case histories of freezing technology applications in the construction of a deep tunnel sewerage system, undersea highway tunnel, and liquefied natural gas tank. Heaving pressure measurements for various soil types around a liquefied natural tank are compared with existing data. In this paper, we present temperature variations at the bottom and side of a liquefied natural gas tank. Our findings show that ground-freezing technology is very effective in controlling ground water infiltration into underground structures as well providing soil reinforcement in the soft ground. 相似文献