Study And Application On Rapid Slope Stability Evaluation Method For Highway

The slope stability problems are getting increasingly prominent with highway construction, especially under the complex geological conditions in mountainous area. During highway construction, problems about high slope stand out once the construction begins, not only because the route is long so that there are a number of slopes along it, but also because geological exploration of earlier stage has only limited contribution. As a result, it is necessary and urgent to construct one complete technical system for rapid slope stability evaluation and make corresponding stability measures when highway is being constructed. So the author constructed one complete technical system for rapid slope stability evaluation in mountain areas by using qualitative analysis and semi-quantitative evaluation way, based on the study on the engineering geological conditions, rock mass structural features, failure models evaluation of excavated slopes along expressway from Tangkou Town to Tunxi City in south of Anhui Province, China. The research findings achieve anticipative aims and make some progresses both in rock mass structures investigation and in rapid slope stability evaluation. The research findings are described as follows:(1) The rapid rock mass structure description system is established for highway slopes in mountainous area, which can be used to rapidly extract geological structure. The specific classification and description systems of discontinuities and geological bodies for highway slopes are put forward. In addition, the rock mass alteration due to slope deformation and failure is studied. The new concept of "rock mass structure unit" is put forward, which synthetically consider the alterations of rock mass characteristics due to geological structure, weathering and deformation.(2) Interaction matrix is adopted to establish relatively complete index system of rapid slope stability evaluation. It consists of seven basic influencing factors that are representative and facile, including slope gradient, slope height, rock mass strength, discontinuities orientation, discontinuities characteristics, discontinuities combination, rock mass structural unit types. The importance and the weight of indexes are semi-quantitatively analyzed with the method of interaction matrix. Based on the different influence degree between interaction of indexes and stability of slopes, the stage of evaluation indexes is studied qualitatively. With the interaction matrices, the quantitive criterion for indexes of rapid slope stability evaluation is established.(3) The method to establish slope instability index (SII) and to select corresponding support schemes are created, based on combination between qualitative analysis and quantitative evaluation. According to the factual slopes characteristics along expressway from Tangkou to Tunxi, the degrees of slope stability are qualitatively divided into five levels, that is, the worst, the worse, the poor, relative stable and stable. The corresponding gradation of SII value is defined based on the quantitive evaluation. Based on the study on slope support types and their application range, combining slope stability level and deformation model, the corresponding support schemes are put forward with the system.(4) A new complete technical system of rapid slope stability evaluation for highway is constructed based on the research findings mentioned above, and the method and procedure of rapid slope stability evaluation are described systematically. There are four parts in the technical system of rapid slope stability evaluation for highway which integrate the organic system, that is, rapid rock mass structural description is the basic means to get engineering geological data, construction of index system for rapid slope stability evaluation is the basis of rapid slope stability evaluation, study on rapid slope stability evaluation method is the key of the rapid evaluation, and supporting schemes selection is the ultimate purpose of rapid slope stability evaluation. Therefore rapid slope stability evaluation can be implemented according to steps as follows: rapid rock mass structure→construction of rapid slope stability evaluation index system→quantification of evaluation indexes→rapid slope stability evaluation→rapid selection of supporting schemes for slopes.(5) The rapid slope stability evaluation method is applied to slopes at highway from Huangshan to Taling and Xiaohe in Anhui Province, China. The practical status of evaluation indexes is studied and quantified based on rapid rock mass structure description. The slopes stabilities are evaluated rapidly by integration of qualitative analysis and quantitative evaluation, and the evaluation results accord with actual slope characteristics. At last the slope supporting schemes are given according to slope stability gradation and engineering geological conditions.