黄土隧道工程地质灾害主要类型及分析评价

【作者】 陈新建；

【导师】 范文；

【作者基本信息】 长安大学 ， 地质工程， 2004， 硕士

【摘要】 黄土是第四纪干旱半干旱特定地区形成的具有特定物质组成和微观结构的特殊土，在古地形地貌基础上继承性堆积形成幔覆结构。颗粒级配、接触关系、孔隙类型和大小、胶联结构类型、状态及特征等关系构成黄土的基本骨架，决定了黄土构造特殊，强度偏低，承载力低，部分具有湿陷性。黄土表现出特殊的工程特性，对工程结构物危害大，为工程界普遍关注并被视为特殊工程地质体，在隧道工程中被视作特殊类型的Ⅱ、Ⅲ类软弱围岩。黄土隧道将黄土作为施作对象，开挖过程极大地改变了黄土体的天然应力状态，随着初期支护和二次衬砌的施作，又改变了黄土围岩的二次应力和三次应力状态，使得原本就复杂的黄土工程特性又经历了复杂的应力调整过程，这一过程使洞室围岩的应力一部分转移到附近区域，另一部分则以塌方等地质灾害形式而释放掉。黄土节理发育，结构强度低，水理性质差，这是黄土隧道的首要难题。 隧道的工程地质条件密切关系到隧道修建时的开挖方法、支护形式以及衬砌结构的类型；围岩工程地质条件既是产生隧道地质灾害的物质基础，又是研究隧道地质灾害的载体，撇开人为因素隧道地质灾害都可以从围岩工程地质条件中找到根源。黄土的物理力学性质、压缩性、湿陷性、击实性、抗剪性、水理性等基本工程地质特性决定着黄土隧道围岩的工程性质。本文结合黄土隧道施工实践过程中出现的主要工程地质灾害，系统论述黄土的土体工程特性-黄土的含义及成因、成分和结构，在此基础上探讨其致灾机理——物理地质作用效应、地震作用效应、水作用效应、区域地质作用效应、综合作用效应和施工效应等，归纳出黄土隧道的主要地质灾害类型。 塌方是黄土隧道最常见的地质灾害，本文分析影响隧道塌方的主要因素(地质因素和施工因素)，从力学方法、赤平投影方法、数值方法、概率方法等途径分析黄土隧道塌方的机理、规律，评价塌方危害；总结了黄土隧道工程塌方的一些新特点：速度快、无征兆，具间歇性、方向性，塌方规模与施工密切相关，地层变化界面处和土石交界处以及地下水汇集处，容易塌方；引入安全系统工程理念和概率方法评价黄土隧道塌方危害，引入灰色模型预测隧道地质灾害。以有限单元法为基础的数值计算仿真模拟分析黄土隧道开挖的力学行为和变形特性的方法具有广阔的前景。 黄土地层中的水对隧道的影响举足轻重，围岩中水的作用是黄土隧道设计、施工时的重点研究内容和关注对象，对一些大的隧洞工程则仍需对其在饱和黄土中成洞的条件和黄土浸水的控制技术进行较深入的研究。黄土中的孔隙，空洞成为地下水有效存赋空间和运移通道，构成黄土的重要含水介质，而隧道开挖后低强度围岩新增节理裂隙又拓展了地下水的空间通道，本文从隧道围岩水的来源和作用分析、评价围岩含水量增高后产生的水危害；分析黄土围岩的水敏感性。黄土中水的作用主要表现为软化作用、润滑作用、溶蚀作用、增重作用、冲击作用和崩解作用，其结果是不仅降低更多还原

【Abstract】 The loess is a special kind of soil which has been forming in the drought and partly drought climate in the Quaternary period. It is composed of particular material constitute and microstructure in particular region and piles up on the ancient physiognomy. The fundamental character depends on the grain series, contacting relationship, hole types and size, joint types, surrounding rock condition and feature. They give the loess special tectonic structure, such as lower strengths, weak bearing power, wet-collapsing partly. Therefore loess reveals special geology engineering character and maybe damages engineering building. The surrounding rock of loess tunnel is regarded as II、III、species . The natural stress are changed during the tunnel’s features, and changed again with the timbering and interfacing, which makes surrounding rock complicated. Some transferred to neighbor, others were released during it collapsed. The prime problem is the up-growth of joint, weak microstructure strength and water-impairing.The engineering geology term of the tunnel is in charge of the tunnel’s excavation method, lining structure forms and interfacing structure. The surrounding rock engineering geology is not only the material foundation of producing disasters in loess tunnel, but also the carrier of studying the geological disasters. The sources of the disasters in loess tunnel can be found out from the surrounding rock engineering geology condition except for the artificial factor. The special geology engineering character of the loess, such as physical mechanics, compressibility, wet-collapsing, shearing, water-impairing etc, which dominate the geology engineering character of surrounding rock of the loess tunnel. Based on the practice of the loess tunnels, this paper demonstrates and studies the effect mechanism of the disaster, then draw a conclusion of the main geological disaster types of the loess tunnels.Cave-ins are dominating within the tunnel disasters. This paper analyzes the main factors that influence the tunnel collapse (geology factor and project factor) and study the disasters-caused mechanism and regularity. Making use of mechanics, stereographic projection, numerical calculation, probability calculation, we can evaluate the danger of cave-ins. New behavioral traits of cave-ins of the loess tunnels engineering are extracted and summarized up. They are rapidity, no premonition, intermittence and direction .The scales of cave-ins also have close relationship with construction. Cave-ins would like to occur where the layer is the interface, the transformation between loess and bedrock, where the layer is threatened by the immerged underground water. Based on the FEM, numerical calculation have remarkable outlook to calculate and imitate the mechanics action and the更多还原