Stability Analysis And Engineering Treatment Of Karst Foundation Of Expressway

The characteristic of karst has the nature of concealment, diversity, complexity. The problem of the karst is one of the most important engineering problems in highway construction in karst area, affects the project of construction and operation safety. The analysis of the stability of karst foundation for highway construction in karst area, can instruct the engineering reasonablely, ensure the project’s quality and safety. Therefore, analyzing the scientific and effective method of the stability of karst foundation, which is of great practical significance to meet the requirement of Engineering construction. The main contents of this paper are as follows:(1) There are many factors affect the formation of the karst and the calamity are influenced, such as the soluble rock, the geological characteristics of the karst and water cycle all has great relation with them. The performance of the groundwater affect the karst is the concentration of the groundwater and surface water, bringing about collapse and funnel. The main performance of the disease caused by the karst to the highway subgrade is the road uneven settlement of foundation, subgrade instability, slope erosion and so on.(2) According to the basic principle of geological radar detection, combined with the general situation of Hunan Henggui expressway project in karst area, developed a karst geology exploration program in the karst areas, analyzing the ground penetrating radar survey line fabric and geological conditions from K79+800to K80+000section. Based on study of geological characteristics in detail, analyzing the features and distribution of the karst development. Result of geological radar shows that Karst development within the study area irregular and poor uniformity, and there exist a large number of caves which have adverse effects on the stability of road foundation. Analysis shows that the means of karst exploration can be directly related to the level of awareness on the karst geology the karst exploration means can be directly related to the level of recognition of karst geology, and also will effect the evaluation results of the bad geological phenomenon of karst and karst disposal.(3) The factors of influencing the stability of karst ground are the strength and occurrence of rock, jointed, the form and size of the external load, groundwater and karst cave fillings and so on. Which have different effection on the stability of karst foundation. Combined with the development characteristics in the Hunan Henggui expressway construction project, with the methods of the qualitative and semi-quantitative of analyzing the stability of karst cave to analyz the foundation of karst, deriving the various methods of karst foundation stability analysis results in good agreement.results.(4) By using the FLAC3D finite difference method software for numerical simulation analysis, studies show that the method of stress, the area of karst cave in different thickness and roof span case numerical simulation of displacement and simulation.The study shows that cave roof in certain circumstances,the more cave spans, the more unstable; Cave spans in certain circumstances, the thicker the more secure the cave roof. The FLAC3D modeling and solving process use the soil constitutive model, the selection criterions of the boundary conditions on the rock, physical parameters and material properties are higher.Numerical simulation method is used in the solving process, to conduct a comprehensive understanding of the karst geological condition, and analyzing with several methods, choosing reasonable parameters, using the simplified model simulation.(5) In the practice of engineering, the treatment of the foundation in karst road is mainly to prevent the collapsion of karst roof or soil cave collapse which cause the road foundation subsidence and damage. Before the treatment of such issues must first conduct a comprehensive understanding of the characteristics of karst development, then according to the actual damage degree of discrimination cave road foundation, choosing a reasonable method of governance.