| Glacial movement took place widely in China in the Quaternary Pleistocene.Moraine is the product of the transportation and accumulation of debris separated from the parent rock by ice water after glacier melting in this period.Affected by geological conditions,climate and later geological processes,moraine is mostly located in medium and high altitude areas with few human engineering activities,so there is little research on it in engineering and academic circles.With the gradual development of Western China and the continuous construction of hydropower,highway,railway and other projects,the engineering geological problems related to moraine are becoming more and more prominent.Among them,the Sichuan Tibet railway is the"century project"connecting Sichuan Province and Tibet Autonomous Region.The Qinghai Tibet Plateau and Hengduan Mountain System crossed by the line are areas with concentrated distribution of Moraine in China.The bridge tunnel ratio of Ya’an Linzhi railway under construction is more than 80%,Such as Queer shan tunnel,Zangga tunnel and Milin tunnel.At present,scholars at home and abroad have studied the formation and evolution,structural characteristics,basic mechanical properties and engineering classification of moraine to a certain extent,but there is still a lack of systematic research on the deformation and failure mechanism of moraine according to its meso characteristics.How to deal with moraine scientifically and effectively in the process of construction is one of the many technical problems to be solved urgently.Based on the statistics and analysis of the existing research data of Moraine in China,this paper summarizes the basic physical and mechanical properties of typical moraine on the basis of a large number of tests and related engineering data;The three-dimensional stochastic model of moraine is reconstructed by using stochastic reconstruction technology and numerical model mesh generation technology.Based on the block discrete element theory,a large-scale triaxial test is carried out to deeply analyze the influence of moraine fabric characteristics and internal medium characteristics on the overall mechanical properties.The main work and research results of this paper are as follows:（1）In the typical Moraine in China,the rock is mainly composed of granite and the soil is mainly composed of silty clay;The moraine body has a wide particle size distribution,the overall shape of the cumulative curve is relatively uniform,showing a"concave"type,the density is generally greater than 2 g/cm3,the water content is generally 5%～13%,it is generally dry,and the permeability coefficient is generally between 10-3～10-4cm/s.（2）The cohesion measured by the existing moraine test is distributed at 10～400k Pa,and the distribution shape is similar to lognormal distribution;The internal friction angle is concentrated in 10°～50°.However,the existing tests are affected by the instrument size effect,removing large-scale rocks and weakening the medium duality of moraine,so that the test results are not completely consistent with the reality.（3）Based on the principle of spatial topological geometry and the theory of point,line and surface position relationship,the three-dimensional random rock generation program and three-dimensional rock random delivery program that can control meso parameters are written in Python language;The problem of random delivery efficiency is solved by using two methods:the sequential delivery of rock according to volume and the rotation of rock after repeated failure.Integrating the two modules of rock generation program and delivery program,a three-dimensional random rock generation and delivery system with controllable meso characteristics is developed,and the results are random and repeatable.（4）Under triaxial loading,the moraine sample shows the phenomenon of dilatancy,and the shear band formed after failure shows a certain phenomenon of surrounding rocks.The shape is asymmetric X-shaped distribution,which is jointly affected by the content of rocks,the spatial distribution of rocks and the size of confining pressure.（5）The shear strength and stiffness of moraine are in direct proportion to the rock content.With the stone content increasing from 5%to 35%,the cohesion of moraine increases by 68.21 k Pa,the internal friction angle increases by 8.63°,and the elastic modulus increases by 50 MPa;At the stage of 15%～30%rock content,the restraint effect of rock on soil particles is enhanced,the shear strength parameters increase sharply,and the moraine changes from"rock suspension"to"soil-rock compaction".Based on the numerical simulation results,the relationship between shear strength parameters and rock content of moraine is proposed.（6）The influence of rock characteristics in moraine on shear strength parameters of moraine is revealed.When the rock content is more than 25%,the spatial distribution will cause the difference of shear strength parameters by 1%～5%,and the difference of internal friction angle is greater than cohesion;At 25%rock content,the sphericity of rock increases by 0.3 and the internal friction angle decreases by about 2°.After failure,the shape of shear zone is smoother,and the influence formula of sphericity of rock of typical moraine with 25%stone content on the internal friction angle is obtained.（7）The influence law of the soil characteristics inside the moraine on the overall shear strength of the moraine is explored.Under the condition of 25%rock content,the cohesion of the calcareous gel frozen moraine is 32.21 k Pa higher than that of the argillaceous gel frozen moraine;The cohesion of moraine with 20%water content is14.78 k Pa lower and the internal friction angle is 6.57°lower than that with 5%water content.The cohesion is more sensitive to water than the internal friction angle.The influence formula of water content of typical moraine with 25%rock content on shear strength is obtained. |
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