| A number of fragmented loose rock bodies are developed in the proposed dam site of the Rumei Hydropower Station.Among them,the SL24 fractured loose rock mass developed on the right bank abutment of the proposed middle dam site area is about 1.5 million squares,and the right bank abutment is excavated.The choice of the scheme has a controlling influence.The stability of the fragmented loose rock mass near the middle dam site also has an important adverse impact on the safe operation of the dam after its completion.Therefore,the research on the development characteristics,engineering characteristics and genetic mechanism of the fragmented loose rock mass in the dam site area is of great significance to the construction and operation of the Rumei Hydropower Station,and has important reference value for similar engineering survey and construction.Based on the analysis of geological process mechanism-quantitative evaluation and system engineering geology,through the study of engineering geological conditions,rock mass structure characteristics,unloading deformation and failure phenomena,and development characteristics of fractured loose rock mass in dam site area;using discrete element numerical simulation The software simulates the river valley undercut and systematically studies the genetic mechanism of the fragmented loose rock mass by qualitative analysis and quantitative analysis.The main research results obtained are as follows:(1)For the ?-level structural plane of the Zhongba site,it is mainly fault,long crack and large fault fault zone;the extension length is 100m~1000m,the fracture bandwidth is generally 10~200cm;the main filling material is fault breccia.Rocks,tectonic breccia,a small amount of silt-filled mud,fault mud,etc.Among them,the long-slit L72 plays a major controlling role in the stability of the left bank slope rock mass;the IV-level structural surface of the middle dam site The NNE group(group II),NEE group(IV group)and NWW group(group ?)are most developed,mainly small faults,extruded surfaces and a few weak interlayers,mostly compressive faults,a small number of strike-slip faults;The V-level structural planes in the site area can be divided into eight groups.The steep slope of the left bank is most developed in the NEE group(IV group),and the steep slope in the right bank is most developed in the near SN group(I group).(2)The engineering geological section of each flat in the middle dam site area was carried out,and the rock mass structure type was qualitatively evaluated and quantitatively evaluated.The rock was calculated by RQD,rock mass coefficient RBI and rock mass structure index RSI.The quantitative analysis of the body structure shows that the rock mass structure type of the left bank of the dam site area is dominated by mosaic structure,and the local part is like a layered structure and a sub-block structure.The rock mass structure in the flat raft gradually gradually changes from the mosaic structure to the flat interior.It develops into a layered structure and a sub-blocky structure;the rock mass structure type of the right bank is mainly composed of a broken embedded structure and a thin layered structure.In the flat rock,the rock mass structure is gradually divided into a flat structure and a mosaic structure.Gradually developed into a layered structure,mosaic structure,in addition,compared with RQD,rock mass coefficient RBI index,the rock mass structure index RSI index proposed in this study can better describe the rock mass structure characteristics and differences.(3)The typical unloading phenomenon in the middle dam site area is analyzed.There are two kinds of unloading of rock mass in the slope of the middle dam site.One is gravity unloading;the other is stress relief unloading,and some are also partially In addition to the composite unloading,the dumping deformation rock mass is developed on the shallow side of the right bank side to the free surface.Gravity unloading mainly occurs in the shallow surface of the slope rock mass,and the mechanism is slip-pull,slip-pressure-induced cracking,and a small part is dumping-pull cracking;the stress relief unloading is located deep in the slope.The mechanism of occurrence is slip-pressure-induced cracking;the dumping-deformed rock mass is mainly developed in the ridge portion where the right bank topography protrudes,and the mechanism is slip-bending,bending-pull cracking.(4)Unloading and zoning of the right bank of the Zhongba site was carried out by qualitative and quantitative analysis of rock mass unloading zoning,Pingshuo seismic wave test and rock mass wave velocity ratio in the dam site area.It can be seen from the right bank PDZ08,the PDZ14 flat and the PD8 flat.The unloading depth and unloading strength of the bank slope show a trend of increasing from the riverbed with increasing elevation in the vertical direction.In the same elevation flat,The unloading modes of rock masses at different depths are also different.In the shallow part of the slope body,the gravity unloading is mainly manifested;in the interior of the slope body,the stress relief type unloading is mainly manifested.In the PD8 flat raft,the rock mass is deformed from 0+30~56m,and the depth of the strong unloading zone is 0~66m.The depth of the PDZ08 flat unloading zone is 0~41m;the PDZ14 is extremely unloading.The belt depth is between 0 and 45 m.(5)The formation mechanism of the fragmented loose rock mass in the middle dam site is analyzed.The main stratum lithology of the dam site is the Pan'an Formation of the Triassic Zhongde Zhuka Formation,and the deformation and failure of the specimen is unsteady.Under the tectonic stress,the Ying'an rock accumulates high elastic strain energy,and the stress balance state changes during the process of river valley cutting.The rock mass adjusts the stress state by deformation to reach a new balance.During this process,the rock mass undergoes deformation and failure,which is mainly manifested by the further expansion of the primary fracture in the rock mass and the formation of many new joint fissures.These native joint fissures and new joint fissures provide a material basis for the formation of fractured loose rock masses.(6)Using the discrete element simulation software,the river valley undercut is simulated.The main understandings are as follows: 1)During the process of river valley cutting,the stress redistribution occurs in the rock mass of the lateral free surface,among which the maximum principal stress trace and lateral direction The airfront surface is nearly parallel,and the minimum principal stress trace is nearly perpendicular to the lateral free surface,and the rock mass near the slope is in a unidirectional or bidirectional stress state.A compressive stress concentration zone appears in the foot of the slope,and a tensile stress zone appears locally in the upper part of the slope.2)In the early stage of river valley evolution,the main deformation and damage occurred at the foot of the slope.As the valley undercut progressed,it gradually developed to the slope foot and the lateral air surface.The depth of the unloading influence gradually increased,and the river valley was cut to the present valley.The unloading mainly occurs in the lateral free surface area,and the superficial reform is intensified in the process.3)At the same elevation,the displacement increments of different parts are different.In the slope surface,the displacement increment of the rock mass is the largest.From the slope surface to the inside of the slope body,the displacement increment is gradually reduced,which is different in the process.The unloading zone,on the monitoring line 5 of the 3085 m elevation,develops a fragmented loose rock mass in the range of 0~80m on the slope table;on the monitoring line 6 of the 2985 m elevation,it develops in the range of 0~70m on the slope table.Fragmentation loose rock mass;on the monitoring line 3 of 2915 m elevation,there is a fragmented loose rock mass in the range of 0~47m on the slope table;on the monitoring line 7 of 2815 m elevation,it develops in the range of 0~38m on the slope table.The fragmented loose rock mass;the fragmented loose rock mass is not developed below the 2780 m elevation,and the results are consistent with the actual situation of the investigation of the fragmented loose rock mass.(7)According to the qualitative analysis of the fractured loose rock mass and the numerical simulation of the slope evolution process,the formation stage of the fragmented loose rock mass is divided into three stages: 1)Ying'an rock unloading During the deformation development stage,due to the undercut of the valley,the stress state of the Yingan rock is adjusted,the stress accumulated in the rock body is released,and the rock mass is deformed and fractured during this process;2)the initial stage of gravity unloading,due to the valley undercut,the valley depth Gradually increase,the vacant surface gradually forms,the stress state of the slope rock mass is obviously different,and the slope stress field is redistributed.Under the action of the self-weight stress field,the unloading deformation of the rock mass is gradually intensified;The fragmentation loose rock formation stage,as the valley cuts down to the current river valley,the slope enters the long-term aging deformation stage.During this process,the shoulders and ridges,such as the thin layered structure and the middle layered rock mass,continue to bend under the action of gravity.In the shallow surface part of the slope rock mass,the combination of gently tilting and steeply inclined joints is formed.Controlling the unfavorable structural plane of the rock mass sliding,the rock mass occurs slip-pull and slip-pressure-induced tensile deformation and deformation.In this process,the rock mass unloading deformation is strong,the rock mass is broken and relaxed,and the fragmented loose rock is formed.body. |
PDF Full Text Request