| With the exploitation of resources and the development of underground engineering,more and more attention has been paid to the research of the nuclear waste disposal and the CO2 seal cover as well as the oil and gas storage.Because of the advantage of low permeability,strong creep performance,the self closing characteristics when the fracture under water condition and the good retention ability of the nuclide,the argillaceous rock formation is a good alternative site for the engineering geological disposal.In this paper,the soft rock,which is the common underground engineering object,was researched.Through the analysis of argillaceous rock constitutive model,seepage characteristics and seepage-stress coupling characteristics,a lot of laboratory tests and in-situ tests was combined to make comparison of the advantages and disadvantages of the commonly used constitutive model of mudstone.The permeability under damage evolution equation and hydraulic behavior under the macro and micro concept of argillaceous rocks was described,the seepage-stress coupling model was established.Through the finite element simulation software ABAQUS,the failure of mudstone under different constitutive model was simulated.And the work progress of argillaceous rock under the condition of seepage-stress coupling was simulated and analyzed.The failure mechanism and permeability operating law were revealed.This paper also analyzes the cracks of mudstone fracture after was damaged,and the initiation,penetration,and self-healing mechanism of crack was preliminarily analyzed.And the characteristics law of crack self-healing and influence factors of crack self healing was searched,as well as the model of mudstone fracture healing was established to provide a good basis for the stability and safety of surrounding rock in major engineering.The main conclusions are as follows:(1)The advantages and disadvantages were compared between mudstone Mohr-Coulomb constitutive model and constitutive Drucker-Prager model,and the application of argillaceous rocks of two model was searched,the results show that the Mohr-Coulomb model can more accurately describe yield characteristics and the failure characteristics of shear zone.The modified Mohr-Coulomb model can not only make up for the previous shortage,but also can describe the strength characteristics of the tension zone.(2)According to the stress-strain characteristics of argillaceous rock,the effective principle was introduced to analyze the coupling of seepage and stress in mudstone,and the influence of effective stress and pore water pressure were taken into account.Through the comparison of method of the total stress and the effective stress method by ABAQUS,it is found that the effective stress can better describe the performance of the rock mass.(3)Combined with the previous commonly finite element software(such as ANSYS,FLAC3D)for the excavation simulation of underground engineering processing method,the ABAQUS in this paper was applied to simulate.The settlement method of the simulation of tunnel excavation,stress release and supporting were given.The Mohr-Coulomb model and Drucker-Prager model were both used to research,and the results show that Mohr-Coulomb model can more effectively reflect the damage situation about surrounding rock tunnel after excavation and support.(4)Mohr-Coulomb model was used to simulate the tunnel support after the excavation and damage in damnification area.The pore pressure and the permeability coefficient as well as the damage displacement of damage zone were analyzed,and the results show that after excavation,with the increase of time,the damage degree of surrounding rock and the pore pressure can increases,the permeability coefficient of groundwater can increases,too.When the excavation is proceed to 12 days,the damage tends to be stable,and the pore pressure decreases gradually,and the permeability coefficient decreases gradually.Finally,the rock was recovered almostly to the initial state.(5)Through the test analysis of the mudstone,it is found that the cracks of the soft clay and hard clay can be healed in different degrees,and soft rock has the fastest healing speed for its mobility.The various factors which can affect the self healing of the mudstone was analyzed.The conclusion was obtained that the main influence factors were the pressure,hydration expansion and saturation time.And finally,the self healing model was established to describe the variation of permeability coefficient. |
