Study On The Stability Of Shizibao Slope By Block Theory In Yuntuo Badong County

The mountain land area is up to 70% of the whole land in China. And the slope engineering problems has been taken more and more attentions as China's western development processing. Slope stability problems researching can provides with reasonable guide for the project planning, design for the selection, excavation works, supporting, monitoring and so on. Therefore, slope stability studying has important project and social significance.Slope can devides into soil slope and rock slope. Researching on rock slope stability, the rock mass must be studied firstly. Rock mass is complex geological body, which composed of rock and discontinuuities. The discontinuyities are the collectively of all the discontinuous plane in rock mass; rock is block in rock mass cutted by the discontiniuities, whose material is relativily continuous and dense to rock mass. The strength of rock mass includes rock strength and discontinuities strength. Normally, the existence of the discontinuities and its strength control the strength and stability of the rock mass. The deformation and failure of test often happens because of the discontinuities occurring opening, closing, dislocation and so on, while the strength of the rock is much higheer than the discotinuities' and its deformation is relatively smaller. If there is no discontinuities, the test is much stable. Therefore, researching on the discontinuities is important to the stability research of rock mass.Block Theory can effectively study the stability of the rock mass cutted by discontinuities. Block Theory analyzes the existence of the rock block from the cutting of the different oriention of the discontinuities, and the occurance of the block on the excavation plane, the form characters of the block, the failure model and so on; during the block stability analysis, from the limit equilibrium method, the stability factor of the block can be calculated, the key block can be searched and the engineer prevention can be designed.Based on this, the application of Block Theory on the research of the slope stability is studied in this paper. The method of the three dimensional randon key block seariching which is based on the discontinuities network simulation is used in Shizibao slope. This paper mainly includes as follow: the current research and application of Block Theroy in domestic and internation is summaried systematicly, the basic method reseaching and application on slope stability by Block Theory is briefly introduced, the discontinuities network simulatin method and the three dinensional randon key block searching, which is based on discontinuities network simulation are studied, which are applicated to the Shizibao slope, its stability is analyzed and the anchorage protection is designed.During the engineering test, the engineering geological condition is surveyed firstly and the discontinuities are classfied into different level. According to its geological construction condition and the generation evolution history, the discontinuities are divided into several groups. The geometry parameters of every group of discontinuities such as dip direction, dip angle, trace, gap, space and so on, are in line with the statistics distribution. Combined with the results of the previous studies, the statistics model and the eigenvalue of every group of discontinuities are determined.Based on the statistic analysis results of the discontinuities, using the powerful previous process ability of ANSYS program, the geometry structure model is established by Monte Carlo method, which solves the complicated problem of the existence of block. The geometry data of block is processed by the programme writen by myself. According to upwards vector of plane which is composed of the block, the planes can be divided into several kinds correspondind to the discintinuities group and the boundary. According to the centroid of the block and the vector of the plane, whether the block is on or below the plane can be identified. The number is decided from the kind of the plane and the location relationship between plane and block. In this way, the geometry structure model of slope and the geometry data are prepared for the further analysis with Block Theory.And then according to the principle of "tangible that is limited"and the excavation plane in the engineering test, the removable block is the isolated part in the caxavation circle in the stereographic projection figure. Under the weight working, from the mechanics analysis, the block in the slope can slide alone one plane S_i and the intersection of two plane S_ij. The slide direction is the projection of the force on the slide plane or the intersection of the two plane. In the stereographic projection figure, the slide mode and its relavative block number are founded out with correlative rule. With the geometry remobable block number, the potential unstable block number is founded out. The strength of the discontinuities is decided by the engineering geological condition and test results. The overplus sliding force F is calculated for every potential unstable block. If F>0, the block is key block, otherwise, it is stable block. Along the searching process of 'limit block-removable block-potential unstable block-key block', the key block is founded out, by which the purpose of searching three dinensional randon key block is achieved.Slope stability status can be analyzed through the geometry characters and stability factors of the key block. The destroying extent and status of the key block in the slope stability is decided by its slide mode, geometry character and size. Analyzing the key block is useful for studying the rule and guide the further prevention design. The amount of the key block, geometry parameters, its volume, its area on the excavation plane and its part after the extension of the wall can show the size and destroying extent of the key block. The three has geometric computing relations and have the same distributiong rule. From the geomotry analysis results of the block, it is found out that, the smaller of the area, the more of the amount. From anasysis of the amount ratio of the key block to the block on the excavation plane, area on the excavation and volume, the ratio of area is the biggest, amount is bigger and the volume is the smallest, which says that, in the three dimensional space distribution, it has absolute superiority of the two-dimensional direction along the excavation plane, while the distribution along the vertical direction of the excavation plane is not very developed.If the area ratio of the key block on the excavation to the excavation is up to a certain extent, the slope is unstable and it must be reinforced. The prestressed anchor, the anchor spray are often used in the block structure slope. the combination of the system anchor bolt and strengthening anchor is used in the small block slope. the length of anchor is considered of its equivalent radius, that is the part after the wall. The reasonable space of the anchor should be consicered the overplus sliding force, the diameter of anchor and the strength of the mortar and so on.Summarily, the character are as follow: (1) based on the discontinuities network simulation, the slope geometry model is established in ANSYS and the block is formed by the plane cutting, which the complex proble of the block existence judgment is solved;(2) the geometroy data is processed by the programe written by myself and the searching of the three dimensitional randon key block is achieved by Block Theory; (3) from the analysis of the geomotry character and stability factor of key block, the slope stability is studied and the prevention for the slope is designed.