| Based on the project "engineering geological characteristics of soft rock and soil mass in Middle Yunnan water diversion project(Wanjia Xinzhuang)and its influence on the project",this paper mainly studies the engineering geological characteristics of silty mudstone in Zhangjiahe formation of Middle Jurassic system in Chuxiong section of Middle Yunnan water diversion project by means of preliminary geological survey,indoor physical and mechanical test and water physical property test In the case of test conclusion and test data,the three-dimensional model of the corresponding research section of Longtan Tunnel is established by using numerical analysis software,and the possible engineering geological problems in the actual construction process are analyzed by simulating the deformation of the tunnel under the pure excavation and corresponding support conditions.The Chuxiong section(Wanjia roots)of the central Yunnan water diversion project is 142.910 km long,with 9 water diversion tunnels totaling 129.68 km long.The Middle Jurassic Zhangjiahe formation mainly consists of silty mudstone,calcareous mudstone,fine-grained feldspathic quartz sandstone and mudstone with fine sandstone.The thickness is 1064.9m ? 1695.9m,which is distributed in Fenghuangshan tunnel and Longtan Tunnel in the middle and back section of Chuxiong section.The total length of the distribution along the line is 9493 m,accounting for 6.65% of the total length of the line section.In this paper,the physical and mechanical properties and water physical properties of Zhangjiahe group silty mudstone are discussed and studied by means of mineral analysis,microscopic observation,uniaxial compression test,direct shear test,triaxial compression test,triaxial rheological test,water permeability analysis,softening analysis,expansion test,collapse resistance test and numerical analysis The microcosmic mechanism of action under water condition is as follows:(1)The argillaceous content of the rock sample is relatively high,which contains more clay mineral components,especially the content of the Yi Meng mixed layer is the highest,followed by the illite,and the composition and content of the clay mineral have a very important relationship with the water physical properties and mechanical properties of the rock.Generally speaking,the rock with higher clay mineral components has a strong expansion and disintegration,which is easy to cause a greater impact on the project Great harm.(2)According to the relevant test results,the overall strength of the sample is not high,and the surface of the sample is prone to muddy after the interaction with water.Through the analysis of softening test,it can be seen that the strength and modulus of elasticity of the sample under the condition of water saturation are greatly reduced and the softening coefficient is relatively low compared with the sample in the natural state,which indicates that the effect of water on the rock sample is very obvious.In addition,the sample is in a single state The axial test has obvious compaction stage and low deformation modulus,which may lead to large deformation in practical engineering.(3)Under the action of water,the rock sample can produce large expansion deformation in a short time.In the early stage of expansion,the effect of water is obvious,and the expansion effect tends to be stable in the later stage of the action.In addition,the surface of the rock sample has certain argillization phenomenon with certain degree of disintegration,which may cause large deformation of the tunnel and certain degree of damage to the support structure in the actual project.(4)Under In the process of "immersion loss of water" cycle,the rock sample will be accompanied by certain degree of disintegration,and its disintegration resistance will gradually stabilize with the number of disintegration tests.The reason is that the content of the hydrophilic minerals in the rock sample will gradually decrease due to the continuous interaction with water,and the final disintegration particles are mainly non hydrophilic minerals,and the reaction degree with water will gradually decrease The conventional disintegration resistance index is also approaching to a certain value.(5)Based on the related physical and mechanical properties of rock samples,the mechanism of swelling and disintegration is analyzed.Generally speaking,the root cause of swelling and disintegration of rock is caused by the hydrophilic substances contained in the rock,which will destroy the connection between the particles in the rock and increase the spacing between the particles;make the dissolution holes in the rock,increase the water and water content The degree of action of hydrophilic minerals and the formation of structural changes caused by particles in rocks.(6)Through the method of numerical analysis,using the finite difference software FLAC3 D to study and compare the displacement change,shear strain increment,stress and plastic zone distribution of Longtan Tunnel under the natural and full water conditions.On this basis,the mechanical response of the surrounding rock of the tunnel under the support is analyzed and the corresponding stress situation of the support structure is obtained. |
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