IMHE OpenIR  > 山地表生过程与生态调控重点实验室
三峡水库水位涨落对消落带土体抗剪强度的影响
Alternative TitleThe influence of alternate submergence and exposure to shear strength of soil in the riparian zone of Three Gorgers Reservoir
吕发友
Subtype硕士
Thesis Advisor贺秀斌
2017
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Discipline环境工程
Keyword三峡水库 消落带 紫色土 抗剪强度
Abstract三峡消落带存在严重的土壤侵蚀和土质岸坡坍塌问题,威胁着库区生态环境和生产安全,明晰在三峡消落带特殊的水土相互作用方式下,岸坡土体物理力学性质(容重、质量含水率、孔隙率、颗粒组成,Ca、Mg、Fe,矿物组成,抗剪强度及其参数)的响应规律,有助于从本质上认识消落带土壤侵蚀机理。因此,本论文通过定位监测、原状土采样测试、室内理化性质分析和模拟实验等手段,测定消落带土壤物理力学指标,数理统计分析等方法,研究在水库周期性蓄水而引起的各种作用(水柱压力、干湿交替、质量含水率)下,消落带土壤的基本物理、化学性质指标,抗剪强度及其参数的响应情况,为从力学角度研究消落带土壤侵蚀机理、科学制定三峡消落带土壤侵蚀方案提供借鉴。本研究得出以下主要结论:(1)土体在淹水过程中受到的水柱压力越大,淹水后在其他条件相同时,紫色土的强度和刚度越大。与初始试样相比,分别在0 kPa和300 kPa水柱压力条件下经过6次干湿循环后的重塑紫色土(干湿循环幅度为ω2),内摩擦角分别降低了44.3%和增加了31.4%,不同的水柱压力对土壤黏聚力的影响不显著;随淹水过程中受到的水柱压力的增加,相同条件下紫色土的应力-应变曲线由应变软化型逐渐过渡为应变硬化型(2)非饱和紫色土的强度、刚度和变形特性均与其质量含水率密切相关。在一定质量含水率区间内,随含水率的增加,相同围压下重塑紫色土抗剪强度值急剧降低,黏聚力增大,内摩擦角减小;土体刚度降低,应力-应变曲线从应变硬化型逐步过渡为应变软化型。(3)干湿循环次数和幅度对紫色土的强度和刚度有显著影响。其它条件相同时,干湿循环次数越少、干湿循环幅度越小,紫色土的强度和刚度越大。随干湿循环次数的增加,重塑紫色土黏聚力以近似稳定的速率急剧降低,内摩擦角总体呈上升趋势,在第3次干湿循环前后有一定的波动;随着干湿循环幅度的减小,相同围压下重塑紫色土抗剪强度值和内摩擦角迅速增大,黏聚力的变化趋势则与之相反;与对照组相比,经历最小干湿循环幅度(ω3)后的紫色土,其内摩擦角增加最多,为84.4%,同时黏聚力降低最多,为92.1%;(4)三峡水库周期性蓄水条件下,消落带表土层(0-10cm)土壤受人为扰动、植被根系、地表径流、降雨击溅、干湿交替等的影响较深层土(10-20cm)更大,消落带土壤的容重、孔隙率、机械组成和抗剪强度参数对淹水作用的响应程度随土层深度增加而递减。(5)淹水前后,消落带土壤的基本物理、力学性质存在显著差异。随水位高程增加,消落带土壤(150-175m段)受淹水周期、淹水时间和水体压力的影响均减小,对周期性蓄水响应程度最剧烈的表土层(0-10cm)的土壤。粒径呈低水位段粗、高水位段细,表层粗、底层细的特征;同一时期,随水位高程增高,黏聚力以先增高后降低的趋势分布,内摩擦角沿水位高程的分布无明显变化。(6) 三峡消落带土壤的常用理化、力学指标和矿物组成之间大多存在相关性。研究区消落带紫色土的黏聚力与土壤质量含水率和水云母含量显著相关,可用回归方程c=140.809-182.447x1-390.969x2(r=0.735)进行描述,内摩擦角仅与水云母含量显著相关,可用回归方程ψ=5.103+109.521x1(r=0.595)进行拟合。
Other AbstractIn the riparian zone of Three Gorgers Reservoir (TGR) soil erosion and bank collapse are serious problems that threaten the ecological environment and soil productivity. Soil-water conservation function can be applied to explore soil erosion mechanisms and clearly understand the pHysical soil erosion mechanics and control the soil erosion in TGR.Therefore, our study is based on position monitoring, undisturbed soil sampling test, indoor pHysical and chemical analysis and simulation experiment, measuring the pHysical and mechanical indexes and soil erosion intensity of the soil that sampled in riparian zone of TGR. We used mathematical and statistical structural equations to establish the relationship among water level fluctuation, soil shear strength and soil erosion. The main conclusions of our study are as following:(1) Water pressure, water mass fraction, the times of dry-wet cycle and amplitude can significantly affect the deformation characteristics of remolded purple soil. The more water pressure, less wet-dry cycle times, lighter amplitude and less water mass fraction, the more shear strength and stiffness of purple soil at the same conditions of other things.(2) The water pressure has a significant influence on internal fraction angle of purple soil during wet-dry circulation. Compared with the control group, the samples that suffered 6-time wet-dry water pressure cycles of 0kPa and 300kPa their internal fraction angle decreases at 44.3% and increase at 31.4%, respectively. (3) With the increase of circulation, cohesion decreases at an appropriate stable rate but internal fraction angle portrays a different trend before and after the 3rd wet-dry circulation. The amplitude during wet-dry cycles shows a significant impact on soil shear strength and its parameters. The less amplitude of wet-dry cycle, the more increase of shear strength and its internal fraction angle of remold purple soil at the same confining pressure, but the cohesion shows inversely. Compared with control group, the soil that suffered the minimum amplitude (ω3) has a maximum increase of internal fraction angle at 84.4%, but cohesion decrease at 92.1% (maximum reduction).Certain soil moisture content shows an observable effect to shear strength and its parameters of unsaturated purple soil. With an increase in the moisture content, shear strength decreased rapidly at the same confined pressure, internal fraction angle increased but cohesion decreased.(4) Periodic impounding of TGR influences soil pHysical properties in riparian zone because of human disturbance, vegetation root system and runoff.Bulk density, porosity, mechanical composition and shear strength parameters of the topsoil (0-10 cm) were more sensitive in response than deep soil (10-20 cm).(5) The basic pHysical properties of riparian zone soil have changed significantly after impounding. With an increase in water level elevation, the soil at riparian zone (150-175m) suffers less wet-dry cycles of flooding time and water pressure.The soil of top layer is more impacted by the fluctuation of water level. Particle size analysis indicated that the sampled section of the study area belongs to silty loam soil.The grain composition becomes coarser as the water elevation level decreases. At the same period, cohesion distribution also followed a V-shaped curve. It remained high at ends and low in the middle. here was a non-significant variation of internal fraction angle with the water level elevation changes.(6) There were some significant correlation between pHysical and chemical, mechanical and materials of soil of TGR. In our study, the cohesion of purple soil of TGR remains a remarkably correlative with the content of moisture and muscovite. Furthermore, it can be signed with the regression equation c=140.809-182.447x1-390.969x2(r=0.735). The internal fraction angle is associated with the content of muscovite, which matches with the regression equation ψ=5.103+109.521x1(r=0.595). 
Pages73
Language中文
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/24610
Collection山地表生过程与生态调控重点实验室
Affiliation中国科学院成都山地灾害与环境研究所
First Author Affilication中国科学院水利部成都山地灾害与环境研究所
Recommended Citation
GB/T 7714
吕发友. 三峡水库水位涨落对消落带土体抗剪强度的影响[D]. 北京. 中国科学院大学,2017.
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