藏东地区藏曲流域复杂古堆积体稳定性研究

发布时间：2018-09-09 09:29

【摘要】：由于活跃的地质构造活动,我国青藏高原东部形成众多规模较大的古堆积体。随着人类工程活动在此频繁开展,工程建设中对大型古堆积体的利用越来越广泛,其稳定性研究显得尤为重要。本文的研究区藏曲河流域位于江达县的同普乡境内,面积约672.7km2。从野外调查出发,结合研究区工程地质条件研究,利用大量室内试验、极限平衡计算、三维数值模拟等手段,本文系统研究了古堆积体的工程地质特性、稳定性影响因素、变形破坏机理、稳定性分析评价等内容,并得到了以下几个方面的认识:⑴藏曲河河谷古堆积体的主要岩土组成为块碎石、碎裂状岩块夹粉质粘土,主要矿物成分为石英、长石、方解石、高岭土、绿泥石、云母等,矿物颗粒多呈细晶~中粒粒状结构,细颗粒含量20%,粒度分布范围广,级配良好,具有粗细颗粒的紧密咬合作用、细颗粒的特殊胶结结构—紧密包裹体以及片状团聚的微观结构3个方面的特征。⑵古堆积体的残余强度与峰值强度相差不大,C、φ值高于松散堆积体;含水率的变化主要体现在内聚力C值的变化上,对内摩擦角φ的影响不明显。动内聚力Cd约为0~4.0Kpa,动内摩擦角φd为14.3~21.9°,φd随破坏振次Nf增大而减小,Cd无明显变化规律。动模量Ed随动应变εd增大而减小,随固结比Kc增大而增大,且在固结围压σ3c与动应变εd相同的条件下,等压固结形成的动模量Ed大于偏压固结。阻尼比λ随εd增大而增大,与σ3c、Kc呈负相关关系。⑶各古堆积体的渗透速度数量级约为10-2~10-3,属低-中渗透性岩土层。水力梯度与渗透速度存在非线性关系,且Re5,表现出层流-紊流的过渡状态,不满足层流运动的达西定律。⑷古堆积体的破坏属于自重应力作用下的溃滑变形。进行极限平衡计算得到德弄弄巴对岸古滑坡堆积体的稳定系数为:小雨工况下为1.27,处于永久稳定状态;暴雨工况下为1.153,处于暂时稳定状态,可能发生失稳破坏。⑸利用FLAC3D进行三维数值模拟,分析小雨和暴雨工况下古堆积体的稳定性发现:(1)与暴雨条件下相比,小雨工况下的应力集中、位移变形以及塑性区范围与数值均较小;(2)两种工况条件下,剪应力集中带均未形成贯通面,表明堆积体均处于整体稳定状态;(3)靠近堆积体表面位置,y方向的位移均指向藏曲河谷,表明堆积体有向外的位移,而z方向的位移方向均为竖直向下,表明堆积体的自重应力是变形发生的重要因素。暴雨下堆积体前部的y、z方向位移变形集中区表明堆积体的变形破坏形式可能为前部变形牵引后部变形导致破坏,与变形机理分析吻合。研究区的古堆积体失稳变形主要是由自重应力引起的,现阶段古堆积体处于整体稳定状态,存在局部不稳定现象。
[Abstract]:Because of the active geological tectonic activity, the eastern part of Qinghai-Xizang Plateau has formed many large paleoaccumulations. With the frequent development of human engineering activities, the use of large ancient deposits in engineering construction is becoming more and more extensive, and the study of its stability is particularly important. The Zangqu River basin in this paper is located in Tongpu Township of Jiangda County with an area of 672.7km2. Based on the field investigation, combined with the study of the engineering geological conditions in the study area, and by means of a large number of laboratory tests, limit equilibrium calculation and three-dimensional numerical simulation, this paper systematically studies the engineering geological characteristics and the factors affecting the stability of the paleoaccumulation. The main rock and soil composition of the ancient accumulation body in the Zangqu River valley of the Zangqu River valley is block gravel, the fractured rock block containing silty clay, the main mineral component is quartz, and so on, the mechanism of deformation and failure, and the stability analysis and evaluation are obtained from the following aspects. Feldspar, calcite, kaolinite, chlorite, mica, etc., the mineral particles are mostly fine-grained ~ medium-granular-like structure, the content of fine particles is 20%, the particle size distribution is wide, the gradation is good, and it has tight bite action of coarse and fine particles. Characteristics of the special cemented structure of fine particles, compact inclusions and microstructures of lamellar agglomerations. 2.The residual strength and peak strength of paleoaccumulations are similar to those of the loose deposits, and the 蠁 value is higher than that of loose aggregates. The change of moisture content is mainly reflected in the change of cohesion C value, but has no obvious effect on the internal friction angle 蠁. The dynamic cohesive force (Cd) is about 0 ~ 4.0Kpa. the dynamic friction angle 蠁 _ d is 14.3 ~ 21.9 掳, and 蠁 _ d decreases with the increase of Nf. The dynamic modulus of Ed decreases with the increase of the dynamic strain 蔚 d, and increases with the increase of the consolidation ratio (Kc). The dynamic modulus Ed of the isobaric consolidation is larger than that of the partial consolidation under the same condition as the consolidation pressure 蟽 3c and the dynamic strain 蔚 d. The damping ratio 位 increases with the increase of 蔚 d, and has a negative correlation with 蟽 3cu Kc. 3 the order of magnitude of permeable velocity of each paleoaccumulation is about 10-2 ~ 10-3, which belongs to low-to-medium-permeability rock and soil layers. There is a nonlinear relationship between hydraulic gradient and permeation velocity, and Re5, shows laminar and turbulent transition state. Darcy's law, which does not satisfy laminar flow, .4 the failure of paleo-accumulation belongs to collapse deformation under the action of self-gravity stress. According to the calculation of limit equilibrium, the stability coefficient of the ancient landslide in the opposite bank of Delanobar is 1.27 under the light rain condition and 1.153 in the rainstorm condition, and is in the temporary stable state under the condition of heavy rain, and the stability coefficient of the accumulation body is 1.27 under the light rain condition, and 1.153 in the rainstorm condition. By using FLAC3D to simulate the stability of paleoaccumulation under the condition of light rain and rainstorm, it is found that: (1) the stress concentration under light rain condition is higher than that under rainstorm condition. The range and value of displacement deformation and plastic zone are small. (2) under two working conditions, the shear stress concentration zone does not form a through plane. The results show that the accumulations are all in a stable state. (3) the displacement in the direction of y near the surface of the accumulation body is directed to the Tibetan bend valley, indicating that the accumulations have outward displacement, while the displacement direction in the z direction is vertical and downward. It is shown that the gravity stress of the accumulation body is an important factor in the occurrence of deformation. It is shown that the deformation and failure of the front part of the accumulation body may be caused by the deformation of the front part of the deposit after traction, which is consistent with the analysis of the deformation mechanism. The unstable deformation of the paleo-accumulation in the study area is mainly caused by the gravity stress. At present, the paleo-accumulation is in a whole stable state and there is local instability.
【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P642.2

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