【作者】 朱崇辉；

【导师】 刘俊民；

【作者基本信息】 西北农林科技大学 ， 水利水电工程， 2010， 博士

【摘要】 目前,我国在水利水电工程土石坝建坝过程中,由于对筑坝土料的水利工程性质认识还不够深入,一般安全系数取值都较高,存在极大的浪费现象,这给国家和人民造成了不应有的经济负担和损失。加快筑坝土料的水利工程性质研究步伐,提高对筑坝土料水利水电工程性质的认识,建设既安全又经济的水利水电工程,为国家节约资金,促进社会发展是水利水电工作者、岩土工作者肩负的历史使命。开展筑坝土料的水利水电工程性质的深入研究不仅可以丰富水利水电工程、岩土工程学科的科学理论,而且可以直接减轻国家在基础建设上的经济负担,因而具有十分重要的理论指导意义和现实生产意义。为了全面深入认识筑坝土料的水利水电工程性质,为将来的水利水电工程建设提供理论和试验依据,本文以筑坝土料的水利工程性质为主线,以水利工程筑坝土料的压实性、渗透性、渗透变形特性以及粘土的抗拉性能为重点,主要依托西安市黑河工程建设实际,根据现有试验条件,开展了筑坝土料的几个水利水电工程性质专题问题的室内试验研究。研究主要内容分为三大部分,即土的最大干密度研究、土的水力学性质研究和非饱和粘性土的抗拉强度研究。在土的最大干密度研究中,对粘性土最大干密度的主要影响因素、含水率对粘性土最大干密度的控制作用、粘性土最大干密度的简便试验方法、超粒径粗粒土最大干密度的试验处理方法和施工控制等问题进行了探讨。在土的水力学性质研究中,主要在粗粒土的渗透系数与其级配指标的关系、粗粒土的渗透变形坡降与颗粒级配参数的相关性、粘性土与砾质土在不同开缝度下的裂缝冲刷变化规律方面进行了探讨。在非饱和粘性土的抗拉强度研究中,采用单轴和三轴两种拉伸方法对非饱和粘性土的抗拉强度进行了试验研究,对比了相同性状非饱和粘性土的抗拉与抗剪强度规律,对二者的内在联系进行了探讨。通过试验和分析,总结出以下几点结论:(1)筑坝土料的最大干密度主要受击实功能和含水率两个因素的影响,在含水率一定的情况下,干密度随击实功能增大而增加,在击实功能一定的情况下,土体的干密度与含水率呈现出正态曲线关系,在某一适中含水率下土体干密度最大,即存在一个最优含水率和最大干密度。土体的最大干密度受含水率的限制,其最大干密度不会超过土体含水率下击实达到饱和状态所限制的最大干密度。(2)采用剔除法逐步剔除粗粒土大粒径料,对剩余料进行最大干密度试验的研究表明:粗粒土最大干密度与剔除量、剩余量之间存在较强的线性相关规律,提出了以此规律进行外推,从而间接求出超粒径粗粒土原级配料的最大干密度思想。根据超粒径粗粒土压实后密度仍呈不均匀性的特点,分析得出超粒径粗粒土压实过程是细料处于最后被压实,压实后各部分土体仍处于密度极不均匀的结论,提出以剔除巨粒组料后的细料最大干密度试验结果为标准,对施工压实质量进行细料最小干密度控制的观点。(3)粗粒土的渗透系数与孔隙比密切相关,在级配一定的条件下,孔隙比越大,渗透系数越大,渗透系数与孔隙比的平方呈现出一种线性正相关关系;粗粒土的渗透系数与粗粒土的不均匀系数密切相关,不均匀系数越大,渗透系数越大,渗透系数与不均匀系数的平方根成线性正相关关系;渗透系数与曲率系数也存在较强的相关性,曲率系数越大,渗透系数越小,渗透系数与曲率系数的平方根成线性负相关关系,在相关分析和回归分析基础上建立了粗粒土渗透系数与级配指标相关的试验模型。(4)粗粒土的渗透变形坡降与颗粒级配存在联系,在某些范围内存在着有一定规律的变化,与不均匀系数,曲率系数在不同范围内存在不同形式的相关。含5%左右细粒组且级配良好的粗粒土渗透破坏一般属于流土型破坏,破坏坡降较大,一般可达到4.5左右,与较多文献中指出的渗透破坏坡降一般不超过1.5的结果相比要高。粘土与含砾土的裂缝冲刷会改变原滤层结构,粘土与含砾土在改变原滤层结构时机理是相同的,由于含砾土比粘土粘聚力弱,受水流冲刷时极易分散,形成比粘土裂缝冲刷孔隙更细的次生反滤层结构,两种性质土料的裂缝冲刷均能形成次生滤层使原反滤层结构变细,保土性能增强,在设置反滤层情况下,裂缝受水力冲刷作用具有自愈功能。(5)非饱和粘性土的三轴抗拉强度与围压有关,低围压下表现为拉伸破坏,高围压表现为颈缩破坏。非饱和粘性土的三轴拉伸试验表明:以不同围压为大主应力,轴向应力为小主应力绘制的摩尔圆,满足库仑准则,物理性状相同的非饱和粘性土,抗拉强度与抗剪强度存在线性相关性,在无抗拉条件对土体进行抗拉测试时,可通过性状相同的非饱和粘性土抗剪强度参数折减计算非饱和粘性土的抗拉强度。本论文主要创新点在于:(1)建立了粗粒土渗透系数与其不均匀系数和曲率系数的相关模型。(2)采用剔除延伸法解决了求取超粒径粗粒土最大干密度问题。(3)提出了采用单点击实试验法进行细粒土击实试验观点,从而可克服常规五点法击实试验费时费力的缺点。更多还原

【Abstract】 Currently, there is a big waste of phenomenon of the dam process of water conservancy and hydropower engineering earth-rock dams in China,it has resulted in great economic burden and loss of the country and the people, it was mainly due to lack of awareness of the hydraulic property and general safety factor value was higher.It was historic mission of water conservancy and hydropower and geotechnical workers that to accelerate the pace of research and awareness of the property of hydro project of dam soil material and to construct the engineering of safe,reliable,economical and reasonable of water conservancy and hydropower and to promote social development and to save money for the state.It was of great guiding significance to the theory and actual production of meaning that to carry out in-depth study of the property of water conservancy and hydropower of dam soil material, it was not only rich in scientific theory in the water conservancy and hydropower and geotechnical engineering,but also directly alleviated the burden on the national economy of the infrastructure.In order to more comprehensive and thorough understanding of the property of water conservancy and hydropower of dam soil material and to provide theoretical and experimental basis for the future water conservancy and hydropower projects, this paper main relying on the actual water conservancy project of Xi’an Heihe, it was main line to the property of water conservancy projects of dam soil material and it was kind of focus on the compaction of soil material, permeability, seepage deformation characteristics and tensile properties of cohesive soil,and the author had carried out laboratory study on thematic issues of some properties of water conservancy projects of dam soil material.Study was divided into three parts, namely, the maximum dry density of soil, soil hydraulic properties and tensile strength of unsaturated clay.(1) In the study of maximum dry density, the author discussed some of the major problems on the clay.They were the main factors of the maximum dry density of clay, water content to maximum dry density of clay controlling, determine the maximum dry density of clay simple method, the oversized coarse grained soil maximum dry density of test handling and construction control program.(2) In the study of mechanical properties of soil water, the author discussed some of the major problems on the soil permeability coefficient of variation They were coarse-grained soil permeability coefficient and the relationship between the graded index, correlation of coarse-grained soil infiltration parameters of slope and particle size distribution and clay and gravelly soil in various degrees of crack slotted changes of erosion.(3) In the study of the tensile strength of unsaturated cohesive soil, the author tested the tensile strength of unsaturated cohesive soil using two methods of the uniaxial and triaxial tension, a comparison of the same traits unsaturated cohesive tensile and shear strength of the law and analysis of the intrinsic link between them.The author summed up the following conclusions through experimental analysis.The first, the dam of the soil maximum dry density mainly affected by two factors of the compaction function and moisture, in some cases,moisture content,dry density increases with the increase of compaction features. Compaction features in certain circumstances, the soil dry density and moisture content would showing the relationship between normal curve, soil dry density was the greatest at a certain moisture content under one medium,in other words there was an optimum moisture content and maximum dry density. The maximum dry density of soil limited by the moisture content, it would not exceed the soil water content under the restricted by compaction to achieve saturation of maximum dry density.The second, remove method used to gradually remove large-size coarse-grained soil material,study materials maximum dry density of the remaining, following an analysis of the law that was a strong linear correlation rules between the maximum dry density and eliminate the amount of residual of the coarse-grained soil. Pointed out the idea that indirect found the maximum dry density of the original grade ingredients of super-size coarse-grained soil after the law of extrapolation.The density of super-size coarse-grained soil compacted was continues to show non-uniform,analysis of compaction process changes in soil dry density, obtained results that fine material was the last to be compacted in the super-size coarse-grained soil compaction process and the various parts of the soil compacted was still very uneven density, pointed out that the view was fine materials maximum dry density test as the standard for compaction quality construction control of minimum dry density of fine materials after the discounting giant grain groups.The third, the coarse-grained soil permeability coefficient and void ratio were closely related to,under the conditions of gradation determined, there was showing a linear positive correlation between them,the greater the void ratio, the permeability coefficient the greater; there was a linear positive correlation between the permeability coefficient and the non-uniform coefficient of the square root of the coarse-grained soil, the greater the non-uniform coefficient,the permeability coefficient the greater; There was a positive correlation between the permeability coefficient and the curvature coefficient of the square root, the greater the curvature coefficient,the permeability coefficient the smaller, The author established a model of related factors of coarse-grained soil permeability and size distribution index based on the correlation and regression analysis.The fourth, there was a link with the coarse-grained soil seepage deformation gradient and the particle size distribution, in certain areas there were some changes in the law, and the asymmetry coefficient, curvature coefficient in the different areas related to memory in different forms.With 5% of the group and the level of fine granular soil with good infiltration and sabotage was generally flow of soil type damage, destruction of large slope, generally up to about 4.5, and more literature that the seepage failure slope was generally not more than 1.5 higher than the results.Crack in clay and gravel soil erosion would change the original filter layer structure, their mechanism was the same as changing the original filter layer structure,as the gravel soil than in clay cohesive force was weak,and it easily dispersed by water erosion, it could form the finer secondary filter with layer structure than the clay when erosion crack.Two kinds of erosion cracks could form a secondary filter layer, This allowed the original filter with thinner layer structure,and soil conservation performance enhancement.Crack had a self-healing function as hydraulic scour.The fifth, there was a kind of relationship between the triaxial tensile strength and confining pressure of the unsaturated cohesive soil, it expressed as tensile failure when confining pressure was low,it expressed as necking damage when confining pressure was high.There were several conclusions after doing the triaxial elongation test of the unsaturated cohesive soil, Mohr circle satisfied the coulomb criterion as drawing with different confining pressures for the major principal stress and axis of stress for the minor principal stress; There was a linear correlation between the tensile and shear strength of the same physical shape of unsaturated cohesive soil; it could be calculated tensile strength of unsaturated cohesive soil that to reduce shear strength parameters of the same characteristics of unsaturated clay, if there was no tensile conditions on the soil to tensile test.The author established a correlation model of the coarse-grained soil permeability coefficient and its coefficient of uniformity and curvature. Solved maximum dry density of the super-size coarse-grained soil by the extension removed method. Pointed out the compaction test of fine-grained soil by the single compaction test method, can overcome the conventional five-point compaction test the shortcomings of time-consuming. These are the innovation of this thesis.更多还原