西藏怒江松塔水电站坝址区中缓倾角裂隙成因机制分析

发布时间：2018-12-19 20:43

【摘要】：中缓倾角裂隙是峡谷岸坡岩体中常见的一种结构面，在许多水电工程中均有揭露。这种裂隙若充分发育，在有侧向结构面存在的情况下，可共同构成岩体的控制控制性边界，进而影响坝址区高边坡稳定性和坝肩岩体抗滑稳定性。所以弄清坝址区中缓倾角裂隙成因机制就显得尤为重要。本文以西藏怒江松塔水电站坝址区岩体为研究对象，在充分了解国内外研究现状的基础上，通过现场勘查和室内资料整理工作，分析研究了坝址区中缓倾角裂隙发育特征以及工程地质特征；进而通过对中缓倾角裂隙典型现象描述，将坝址区中缓倾角裂隙进行分类，并针对每种裂隙分析其成因机制；最后通过采用应变软化模型和蠕变模型对怒江河谷进行分阶段下切模拟，分析了中缓倾角成因机制和间隔分布现象。具体研究内容及成果如下：（1）中缓倾角裂隙总体特征研究 1、松塔坝址区中缓倾角裂隙右岸以NNE-NEE倾SE为主，左岸以NNE-NEE倾NW为主，呈倒“八”字分布在河谷两岸。总体呈上陡下缓。 2、中缓裂从坡表到山体内部的分布可明显分为多裂隙段和少裂隙段（原岩段），其中在多裂隙段中缓裂也呈间隔分布。 3、中缓倾角在平硐内一般延伸长度在10m以内，其中又以1～3m裂隙居多。计算得到各平硐连通率基本在30～60%之间，说明中缓倾裂隙尚未构成底滑面，仍处于表生改造阶段。 4、通过对中缓裂工程性状分析，可知坝址区大部分中缓裂为性状较好的硬性结构面。（2）中缓倾角裂隙成因机制分析 1、原生型中缓倾有两种：1）岩脉侵入基岩时的隐节理在后期河谷下切中显现；2）花岗岩冷却过程中形成的席状裂隙。 2、构造型中缓裂有两种：1）可能因岩浆活动引发的低角度正断缓裂；2）由里德尔切变效应产生的与陡裂伴生的中缓裂。 3、表生型中缓裂有三种：1）差异卸荷回弹产生的近水平剪切裂隙；2）谷底水平应力集中产生的压剪裂隙；3）岸坡侧向卸荷形成的张性、张剪性裂隙。（3）中缓倾角裂隙成因数值模拟通过数值软件，采用分区破裂化理论和蠕变理论，利用应变软化模型和黏弹塑性蠕变模型，根据怒江河谷演化历史，对其进行分期次下切模拟，验证了河谷在下切过程中，岸坡应力场重分布，岸坡表部出现压制拉裂区和谷底坡脚的剪应力集中区，是表生型中缓倾角裂隙的主要成因。另外通过观测剪应变增量在不同下切阶段随水平方向的迁移，基本解释了坝址区中缓裂间隔分布现象。
[Abstract]:The moderate dip angle fissure is a common structural plane in the slope rock mass of canyons, which has been exposed in many hydropower projects. If this kind of fissure is fully developed, the controlling boundary of rock mass can be formed together under the condition of the existence of lateral structural plane, which will affect the stability of high slope and anti-slide stability of abutment rock mass in the dam site area. So it is very important to make clear the formation mechanism of slow dip crack in dam site. This paper takes the rock mass in the dam area of Songta Hydropower Station of Nujiang River in Tibet as the research object, and on the basis of fully understanding the present research situation at home and abroad, through on-the-spot investigation and indoor data sorting work, The development characteristics and engineering geological characteristics of moderate dip fractures in dam site area are analyzed and studied. Then by describing the typical phenomena of moderate and gentle dip fractures, the fractures in the dam site are classified, and the genetic mechanism of each kind of fractures is analyzed. Finally, by using strain softening model and creep model, the formation mechanism of moderate dip angle and the phenomenon of interval distribution are analyzed. The specific research contents and results are as follows: (1) study on the general characteristics of moderate dip angle fissures. 1. In the Songta dam area, the NNE-NEE tilting SE is dominant on the right bank and the NNE-NEE tilting NW is the main one on the left bank. The word "eight" is distributed on both sides of the river valley. The overall appearance is steep and slow down. 2. The distribution from slope surface to mountain body can be obviously divided into multiple fissures section and little fissure section (original rock segment), in which the distribution of slow crack is also spaced in multi-fissured segment. (3) the average extension length of moderate dip angle is less than 10 m in the adit, in which 1 m crack is the most. The calculation shows that the connectivity rate of each adit is between 30 and 60%, which shows that the moderate slant fissure has not yet formed the bottom slip surface, and is still in the stage of supergene transformation. 4. Through the analysis of the middle slow cracking engineering characters, it can be seen that most of the middle slow cracks in the dam site are hard structural planes with good properties. (2) the genetic mechanism of moderate and gentle dip fractures 1. There are two types of primary gentle dip fractures: 1) the cryptic joints of the vein intruding into the bedrock appear in the later valley, 2) the sheet fractures formed during the granite cooling process. 2. There are two types of slow fracture in the tectonic type: 1) low angle positive fault induced by magmatic activity, 2) moderate slow fracture associated with steep fracture caused by the Rydell shear effect. 3. There are three types of slow fracture in the epigenetic type: 1) the near horizontal shear fissure caused by differential unloading springback; 2) the compressive shear crack caused by horizontal stress concentration at the bottom of the valley; 3) the tensional and tensional fracture formed by lateral unloading on the bank slope. (3) numerical simulation of the causes of moderate and slow dip fractures by numerical software, using the theory of zonal fracture and creep, using strain softening model and viscoelastic-plastic creep model, according to the evolution history of Nujiang River valley, It is verified that the redistribution of slope stress field in the process of down-cutting and the shear stress concentration area in the face of bank slope are the main causes of the moderate dip fractures in the supergene type by stages of down-cutting simulation on the slope surface and the shear stress concentration area at the foot of the bottom slope of the valley slope. The results show that the stress field of the slope is redistributed during the down-cutting process of the valley. In addition, the phenomenon of slow crack interval distribution in dam site is explained by observing the migration of shear strain increment with horizontal direction in different lower shear stages.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV221.2

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