The Water Rock Interaction Of Red Beds In Central Yunnan And Its Influence On Tunnel Engineering

The red layer soft rock is sensitive to water.The strength decreased obviously and the softening was strong when meeting water,which is closely related to the content and type of clay minerals and the structural characteristics of soft rock.The essence of water rock interaction is the change accumulation of its microstructure and the change of macro mechanical properties is the external manifestation of the change of microstructure.The engineering mechanics characteristics are mainly studied based on the experimental study on the silty mudstone of the J2 z.Then the microscopic mechanism of water rock interaction in the soft rock is studied and analyzed.Influence of water rock interaction on micro parameters,mechanical response of tunnel surrounding rock and stress of lining structure are studied by means of numerical simulation.The main achievements of this paper are as follows:(1)There are more clay minerals in the silty mudstone,and the strength is not high.In the compression test,there is a very obvious compaction stage,the deformation modulus is small,easy to cause large deformation.After water saturation the mechanical properties are poor,and the uniaxial compression is mainly in the form of flake spalling failure.After the test,it will generally disintegrate.After 4 days of flooding,the intensity attenuation can reach more than 90%.(2)The silty mudstone of J2 z reacts rapidly with water,the time of disintegration and expansion is shorter,the swelling force is relatively large,and the swelling potential is higher,which effects on the tunnel project.Its resistance to disintegration is closely related to the number of cycles,and the disintegration index is stable with the increase of the number of cycles.(3)The saturation has great influence on the macro mechanical properties of the silty mudstone in the J2 z,and he peak value of saturation is 4 times higher than that of elastic modulus of 100% by 60%.In a certain degree of saturation,the mechanical properties of the process of water loss increase rapidly and then slowly rise,but it is easy to produce shrinkage cracks in the process of water loss.(4)The diagenesis of the silty mudstone is mainly the swelling of clay minerals(including the expansion of the interlayer of montmorillonite and the formation of double electric layer)and the dissolution mechanism of cement.Under the combined action of both,the microstructure of rock is changed,the connection between the particles is weakened,the porosity increases,the micro cracks develop,the physical and mechanical properties decrease.(5)Study on the microscopic parameters under dry and saturated conditions,the rock saturated by PFC2 D results show that the full microscopic parameters under the condition of water than in the dry state,have greatly reduced,water rock interaction strongly effect on rock microstructure.At the same time,the influence of water rock interaction on the mechanical response of surrounding rock and the stress of the lining structure are studied by FLAC3 d simulation.