共查询到20条相似文献，搜索用时 31 毫秒
1.
On experimentally deposited kaolinite, illite, and Ca-bentonite consolidated under their own load or by additional vertical pressure, the progress of compaction in relation to excess pore water pressure, mass physical properties, gravitational mass movements in a tilted tank, and erodibility under running water in a flume were studied. The very low consolidated sediments near the mud/water interface do not obey the generally used theory in soil mechanics. They show a different, non-linear relationship between void ratio or water content and depth below the sedimentary surface on the one hand, or effective overburden pressure and shear strength on the other. The same is true of other physical properties such as permeability, which changes considerably with depth and time of consolidation. High sedimentation rates on slopes induce shallow sediment flow, whereas at low rates and critical slope angles different types of slope failures including the breaking up of water-rich sediment into sharp boundered blocks are observed. Flume studies on soft clay muds show three different types of erosion: continuously suspending, discontinuous erosion of crumbs or shreds, and wavy deformation of the clay surface with disintegration of particles from the crests. The critical tractive stress depends not only on clay type, void ratio, and shear strength, but significantly also on the ‘geologic history’of the clay (i.e. deposition from thin suspension or dense slurry, fabric, consolidation and swelling generating minute inhomogeneities etc.). The experiments may lead to a better understanding of all mechanical processe's including pore-water flow taking place near or not far below the sediment/ water interface. 相似文献
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采用Barron轴对称固结及大变形固结问题的某些简化与假定,推导建立了砂井地基大变形固结控制方程,利用建立的双层砂井地基大变形固结方程及编制的计算程序,通过引入软土渗透系数、有效应力与孔隙比之间的幂函数关系k =ced与e=a( )b,对瞬时加载下双层砂井地基固结性状进行算例计算。结果表明：（1）双层软土幂函数渗透关系及压缩关系中诸参数对双层砂井地基固结性状有重要影响：随着两层软土幂函数渗透关系中参数c1、c2的增加（渗透性增加）、或幂函数压缩关系中参数a1、a2的增加,各土层水平径向与竖向孔隙比减小更快,沉降发展速率与超静孔压消散速率也相应增加,且沉降发展速率快于孔压消散速率。（2）两层土在分界面处的孔隙比及平均超静孔压均出现明显的突变,将沿深度分布曲线分成形状不同的两段,表现出不同的固结性状。 相似文献
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The hydro-mechanical behaviour of a clay-based buffer material for nuclear waste disposal has been investigated in a laboratory program. In this program, the main focus was on the influence of confinement on water uptake and swelling pressure during suction decrease. The laboratory program and some of the results are presented by Dueck [Dueck, A., 2006. Laboratory results from hydro-mechanical tests on a water unsaturated bentonite. submitted for publication.].
The results from the laboratory tests were used to find a relationship between water content, void ratio, swelling pressure and suction. Two equations for swelling pressure represent the outline of the model.
In the first equation, the swelling pressure developed during water uptake is normalised by a pressure corresponding to the swelling pressure at saturation. This is done in order to be independent of void ratio. A relationship between the normalised swelling pressure and the degree of saturation is suggested.
The second equation describes a relationship between the swelling pressure, the water content and the actual suction (or relative humidity). The equation is based on a thermodynamic relationship and includes the retention curve (i.e. water content vs. suction under free swelling conditions).
The model can be used for a state where two of the four variables; water content, void ratio, swelling pressure and suction are known and can thus be useful to evaluate field measurements and model late stages of the wetting process. An example of an application is given. The equations are mainly based on results from tests with increasing degrees of saturation under constant void ratio but are also suggested for use with increasing void ratio. 相似文献
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为了研究土的现场原位与室内试验抗剪强度指标的关系,根据饱和土固结理论,土的固结过程就是在某一压力作用下有效应力增大、孔隙水压力消散的过程。因此,随着有效应力增大土的孔隙比减小,而土的抗剪强度增大,土的压缩曲线与土的抗剪强度线之间有一一对应关系,从土的现场原位和室内压缩曲线出发,研究了加、卸载过程中土的抗剪强度的变化规律,然后根据土的卸载抗剪强度的计算方法推导出土的黏聚力和土的内摩擦角两者之间的相互关系,最后分析得到了原状土抗剪强度的计算方法 相似文献
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盐腔内回填碱渣沉降固结特性室内试验研究 总被引：1，自引：0，他引：1
碱渣回填到充满卤水的废弃盐腔后,颗粒会自由沉降到盐腔底部形成沉积层,进而在自重作用下固结。为了解盐腔内回填碱渣的沉降固结特性,以江苏淮安地区碱渣为对象,进行了沉降柱试验和固结试验。试验结果表明:(1)碱渣在卤水中的沉降过程可以分为3个阶段:絮凝阶段、沉降阶段和固结阶段。初始浓度对碱渣的沉降曲线和沉降速率有很大的影响。(2)碱渣颗粒分布、密度、含水率和孔隙比均呈现出分层特性,颗粒粒径、密度随深度的增加而增大,含水率、孔隙比随深度的增大而减小。(3)碱渣具有很高的压缩性,压缩系数a1-2为3.36 MPa-1。在压力范围小于100 kPa下,固结系数随固结压力的增加而显著减小。试验结果对了解盐腔内回填碱渣的沉降固结特性提供了参考,有利于指导回填施工工艺和碱渣的后期处理。 相似文献
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利用自行设计高压固结仪对5种不同含砂率的饱和砂-黏土混合物开展一系列高压压缩试验,研究砂-黏土混合物压缩性和渗透性演化规律及其对矿物组分的依赖性。试验结果表明,饱和砂-黏土混合物的孔隙比-压力(e-lgP)曲线随着含砂率增高呈现出指数函数模式向双曲线函数模式转化,而e-P曲线在压力高于8.1 MPa则呈线性变化,其斜率依赖于含砂率。最优含砂率随固结压力的增大而逐渐从75%移向30%。不同含砂率的砂-黏土混合物的孔隙率、固结压力和含砂率存在统一的幂函数关系。渗透系数与含砂率有关,渗透系数与孔隙率符合指数函数关系。从砂-黏土混合物骨架结构和孔隙类型的角度出发,从本质上分析含砂率、固结压力对混合物压缩性和渗透性的作用规律。结合SEM微细观结构观测结果,验证砂-黏土混合物骨架结构与含砂率之间的相关性。 相似文献
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一维饱和冻土融化固结分析 总被引：3，自引：2，他引：1
冻土的融化固结是在融化的基础上进行的,是温度与变形耦合作用的结果.根据考虑冰水相变的热传导方程和水分迁移方程,建立以孔隙比为变量的融化变形固结理论.利用有限元软件对冻土一维融化固结进行数值模拟,分析了融化过程中孔隙比、孔隙水压力、变形等随时间的变化规律,并与实验结果进行对比.研究表明：含水率的增大会阻碍融化锋面的推进速率,进而降低土体固结速率,而且冻土的固结过程滞后于冻土的融化过程.随着融化锋面的移动,固结区域不断增大.冻土的融化固结过程也是孔隙水的消散过程,随着孔压的不断消散,变形量逐渐增加.最大位移出现在土体表面,最大沉降量随时间增长而增大,最后趋于一个稳定值. 相似文献
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Based on the fundamental conception soil mechanics, by experimental research, the relation of the coefficient of permeability K to the void ratio e and that of the coefficient of compression aγ to the effective consolidation pressureσ’ are first expressed for normally consolidation clays. Hences the expression of relation of the consolidation coefficient cν to the void ratio e or the effective consolidation pressures is given. There are three typical cases of variation of the consolidation coefficient for different soils types, i.e. the value Cν decreases with the void ratio’s decrease; the value Cν increases with the void ratio’s decrease and the value Cν is essentially independent of the void ratio. Specific variation of the value Cν for specifically soil type is pointed out. The physical foundation for the variation of consolidation index m is explained. The relationships between the value m, the effective consolidation pressure σ’ and the soil layer thickness H are discussed. Finally, correlation between the value Cν and m’s variation as well as the noteworthy problems in practice are represented. 相似文献
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粘土固结参数变化的分析 总被引：1，自引：0，他引：1
本文依据土力学中已建立的基本概念,通过试验研究,首先找出正常固结粘土的渗透系数K与孔隙比e的关系,压缩系数a_V与孔隙比e或有效固结压力σ′的关系,从而推导出固结系数C_V与孔隙比或有效固结压力的关系表达式。分析不同土类固结系数的变化,归纳出三种典型的情况,即:C_V随e的减小而减小;C_V随e的减小而增大和C_V基本上与e无关。并指出特殊土类的C_V有特殊的变化规律。其次,分析了固结指数m变化的物理依据,讨论了m值与有效固结压力和上层厚度H的关系,最后,说明C_V和m变化的相互关系以及实用计算中应注意的问题。 相似文献
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Si-jie Liu Xue-yu Geng Hong-lei Sun Yuan-qiang Cai Xiao-dong Pan Li Shi 《国际地质力学数值与分析法杂志》2019,43(4):767-780
The system of vacuum pressure combined with vertical drains to accelerate soil consolidation is one of the most effective ground improvement methods. The consolidation theories of soft soil improved by vertical drains including void ratio–dependent compressibility and permeability have been widely applied in practice to predict the consolidation behavior. In this paper, analytical solutions of the consolidation of vertical drains are derived incorporating the loss and propagating stage of vacuum pressure. In addition, special solutions are obtained for the cases of instantaneous surcharge loading and staged surcharge loading, based on the general solution. The solution is verified by ignoring the propagating stage of vacuum pressure formation and comparing it with an existing solution. The effects of vacuum pressure loss and propagating stage combined with other parameters are investigated through the ratio between excess pore water pressure and surcharge loading. 相似文献
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沉积形成的水底黏性泥砂自重固结过程表现出显著非线性大变形固结特征,应采用大变形固结理论进行泥砂沉积固结计算。基于软黏土一维非线性大应变固结理论,应用有效应力、渗透系数与孔隙比间扩展幂次函数固结本构关系,由达西定律、有效应力原理、连续介质方程等建立大变形固结控制方程,根据固结单元孔隙水渗流、单元变形与泥砂沉积层固结沉降耦合关系形成黏性泥砂大变形自重固结数值模型。泥砂自重作为固结荷载,数值模型假定沉积泥砂各向同性且固结沉降应变、孔隙水渗流仅发生于竖直方向,为一维单向沉积固结过程;采用泥砂沉降柱试验确定泥砂非线性扩展幂次函数关系参数。模型应用中,划分竖向固结单元,由沉积泥砂固结本构关系确定各固结单元有效应力及超孔隙水应力,通过超孔隙水应力时间维度上的消散过程及各固结参数间的耦合关系计算泥砂固结沉降。数值模型计算结果表明,沉积黏性泥砂自重固结初期表现为有效应力调整过程,初始有效应力与孔隙比根据固结本构关系匹配调整为扩展幂次函数关系;沉积泥砂应变与应力固结度存在20%左右误差,泥砂固结沉降发展快于超孔隙水应力消散过程,证明沉积泥砂固结沉降变形的发展与超孔隙水应力消散并非同步耦合。计算模型应用于室内沉降柱试验模拟淤积黏性泥砂自重固结沉降预测中,模型输出与试验结果符合良好。 相似文献
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通过大量对比试验系统研究了广东典型软土的蠕变固结特性和计算模型。试验结果表明：软土的固结和次固结在变形中所占比例和发生受多种因素影响,包括初始荷载、加荷比、土体固结度、含水率、孔隙比;次固结系数与土体的应力历史、当前固结状态及加荷比有关,在预压荷载下会明显减小;次固结系数与压缩指数之比一般为常数,其值在0.025?0.10之间;剪切蠕变特性与土体所承受的固结压力有关,土样蠕变规律呈应变硬化特征;三轴蠕变特性与排水条件关系密切,固结作用可以削弱蠕变效应;同等加荷条件下,偏应力-轴向应变关系在排水剪切中呈线性关系。而在不排水剪切中呈非线性,并有明显的屈服特征;不排水剪切条件下持续加荷的加荷方式可以适当提高不排水强度。根据上述试验成果分别从考虑非线性本构关系和考虑排水条件分析了蠕变固结模型的建立路径。 相似文献
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This paper presents the variations of void ratios, compression coefficients, compression index and compression modulus of Xiamen muck with consolidated pressure at beginning. The second section describes the laws of coefficient of consolidation variation with pressure or void ratio. At last, it is discussed that the pressure secondary consolidation deformation develops with time at a given constant temperature and pressure. The ratio of secondary consolidation deformation to primary’s one, and quantitative relations between secondary consolidation deformation and pressure are described. 相似文献
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连云港浅层海相软土沉积环境及物理力学性质研究 总被引：21，自引：7，他引：14
海相沉积软土在连云港有3层分布,他们在各自不同年代沉积,而浅层的软土对高速公路工程中路堤的变形和稳定 性有很大影响,该土层在工程中备受关注。本文对连云港浅层软土的沉积环境,物理力学性质和结构性进行探讨和分析。收 集的资料表明连云港浅层的软土是在全新世黄骅海进到19世纪60年代期间沉积形成的,其沉积历时漫长。统计表明该浅层 软土含水量高、原位十字板剪切强度和有效上覆应力的比值约为0.2～0.4。最后根据Burland的理论分析了该层软土的结构 性,结果表明连云港表层的海相软土为高位结构软土,土样易受到扰动,导致室内强度的失真。 相似文献
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Aliakbar Hajimohammadi Seyed Majdeddin Mir Mohammad Hosseini Akbar Cheshomi 《Environmental Earth Sciences》2010,61(4):813-820
Shear wave velocity is one of the important factors representing the dynamic characteristics of soil layers. Hence, many researchers
have focused their studies on determining shear wave velocity by direct field measurements or expressions developed by other
soil parameters. The shear module and damping ratio of the soil layers also play a similar role in the majority of dynamic
soil response analyses. Nevertheless, since they have to be measured in the laboratory by resonant column or cyclic triaxial
tests on undisturbed samples, the possibility of preparing such samples and the reliability of the obtained results are of
great concerns. In the present study, great effort has been made to determine the above dynamic factors by means of field
data obtained from a versatile instrument, namely the seismic piezocone (SPCTU), and to derive expressions correlating them with some parameters obtainable by much simpler instruments. The reliability
of laboratory measurements on undisturbed samples is also evaluated. The seismic piezocone test apparatus has been employed
to evaluate the soil properties at 1-m depth intervals by means of measuring tip resistance, sleeve resistance, pore pressure
and shear wave velocity. The shear module and the damping ratio are calculated using field data. Meanwhile, in order to assess
the laboratory measurements of these parameters, some resonant column tests and cyclic triaxial tests on undisturbed samples
of the same soil layers have been carried out. In order to compare the field results of shear modulus and damping ratios with
those obtained from laboratory tests, the influences of the soil nature and sample disturbance on the conventional laboratory
methods are evaluated and discussed. The shear wave velocity is correlated to overburden pressure and the corrected tip resistance
for two groups of fine soils, namely silty clays and carbonate clayey silts, which mainly cover the areas under study in this
project, are located in southern parts of Iran near the Persian Gulf. According to the results of the present study, there
are narrow limits of shear modulus regarding soils for which the laboratory tests and the field measurements yield approximately
the same shear modulus. This limit of shear modulus is about 30–50(MPa) for clay deposits and 70–100 (MPa) for sandy deposits.
Also the shear wave velocity can be calculated by a simple expression from total overburden pressure and the tip resistance
of simple cone penetration test results conventionally available in many soil explorations prior to engineering practices.
However, if the pore pressure inside the saturated soil deposits can be measured by a piezocone apparatus, the shear wave
velocity may be calculated using another suggested equation in terms of effective overburden pressure in the present study.
Regarding the shear module and the damping ratio, due to the disturbances of the stiff deposits in the sampling process and
great deviations of laboratory results from field results, the laboratory measurements of these parameters out of the above
limits are not recommended. 相似文献
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P. Kallioglou Th. Tika G. Koninis St. Papadopoulos K. Pitilakis 《Geotechnical and Geological Engineering》2009,27(2):217-235
The paper presents results from a laboratory investigation into the dynamic properties of natural intact and model organic
soils by means of resonant-column tests. The natural intact organic soils were sands, cohesive soils and peats with varying
content of calcium carbonate. The model organic soils were formed in laboratory by mixing kaolinite and paper pulp. The influence
of various soil parameters, such as strain level, confining stress, void ratio, plasticity index, organic content and secondary
consolidation time on shear modulus, G, and damping ratio, DT, is presented and discussed. The test results on natural organic
soils show that only high organic contents (OC ≥ 25%) have significant influence on G and DT at both small and high shear
strains. For the model organic soils, however, a significant influence of even lower values of organic content (5% ≤ OC ≤ 20%)
on G at small strains and DT at both small and high strains is observed. 相似文献