| The construction of planningthe station of Banda hydropower is located in the river section of the upper reaches of the Minjiang River in Tibet,which is located on the southeastern edge of the Qinghai-Tibet Plateau and is formed by strong neotectonic movements that form the canyon landscape.During the evolution of valleys and valleys,because of the intermittent uplift of the earth's crust and the erosion and erosion of rivers,the strain energy stored in the high-strength and impervious dacite was released,resulting in the unloading and rebound of the rock mass in the valley,and the unloading.The unloading fractures produced by the charge may become the controlling structural planes in the rock mass of the bank slope,resulting in complicated and varied engineering properties of the slope rock mass.Through on-site field geology survey and intra-fissure intra-fissure record analysis,it is found that the shallow surface layer of the slope generally develops a loosely-cracked rock mass formed during unloading,the rock mass is unloaded strongly,and the dumping deformation is the main damage,and the unloading fracture within the slope develops.The unloading depth of the slope shows an increase with the increase of the elevation,and the unloading depth of the mountain beam is greater than that of the ravine.This paper takes the abutment slope on the right bank of the dam site of Banda Hydropower Station on the Lancang River in Tibet as the research object,and analyzes the geological conditions of the slope,the characteristics of the rock structure,and the weathering unloading characteristics,using physical simulation experiments and discrete element(UDEC)pairs.The river valley was cut and simulated.Finally,the factors influencing the unloading development of the rock mass were discussed.Then the unloading formation mechanism of the rock mass on the right bank slope of the upper dam site was analyzed and the stability of the right bank slope was evaluated.The main research results of this article are as follows:(1)According to the geological survey data of the former dam site area and the field investigation of the Heping Cave fissure record,the structural plane developed on the right bank abutment slope is classified into three classes: grade ?,grade ? and grade ?,and based on the investigation data of a large number of adit,The weathering characteristics of unloading rock mass on the right bank abutment slope are summarized,and the weathering zone of rock mass in the dam site area is qualitatively divided into strong weathering,weak upper weathering,weak downweathering and breeze weathering ~ freshness,and the method of combining qualitative and quantitative analysis is adopted.According to the main quantitative indexes,the unloading zone of bank slope rock mass is divided.The results are strong unloading,weak unloading and unloading.At the same time,the spatial distribution of unloading of rock mass in dam site is analyzed;(2)the structural characteristics of slope rock mass and the classification of slope rock mass quality are found out and analyzed.The rock mass structure from the slope surface to the deep of the slope is basically a granular structure ~ fragmentation(block)structure ~ mosaic block structure ~ block whole structure.The quality of rock mass can be divided into three grades: grade ?,grade ? and grade ?,and the distribution area increases with the elevation.(3)Based on physical simulation test of incised valley simulation studies show that as the incised valley,slope is to reduce stress on the whole,the same highly reduced there is also a difference of different depth,slope near the table of the measuring point pressure change is bigger,and in the slope of the unloading rock mass fracture cracks,at the same time,POE moved along with the monitoring instrument is gradually increasing with depth near the slope table trend of slope displacement deformation more strongly than the bottom and top displacement compared with discrete element software state of the simulation results,both are consistent.Finally,according to the similarity theory,analysis of the prototype and the model of unloading depth and height curve,found in more than 3000 m elevation slope unloading depth generally increases with the increase of elevation,local terrain factors influence,ridge site of unloading depth is greater than the mountain gully,lead to the characteristics of unloading of slope rock mass has a unique and cracking phenomena of the major causes of that accompany with slope gradient and slope height,lithology,rock mass structural plane,rock mass structure type,regional tectonic stress evolution history and river valley,in the role of internal and external factors of comprehensive,formed the right dam shoulder slope characteristic of the rock mass unloading characteristic;(4)Through the analysis of the development characteristics of the controlling structural plane of the right dam abutment slope,the possible instability mode of the slope deformation and failure is obtained.Based on the finite element software FLAC3 D and rigid body limit equilibrium method of the typical profile model is established,the dam site on the right abutment of natural slope stability evaluation under different working condition(natural,rainfall)analysis found that both under natural conditions,slope as a whole are in a stable state.And under the condition of rainfall,the former occurs in the top small value of tensile stress,shear plastic zone at the end of loose cataclastic rock mass and the strong unloading zones enrichment near the boundary,only a loose in cataclastic rock mass shear plastic zone at the local,local sliding of loose rock mass slope surface rupture,but the overall stability of slope body is better,while the latter is under extreme conditions(earthquake,storm)stability coefficient is 1.0 ~ 1.05,the more unstable,may produce partial failure,comparing the two results,overall,the whole stability of slope is better. |
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