| In the deep excavation and resource extraction process,with the mining depth continues to increase,the original geological soft rock or hard rock may be transformed into engineering soft rock in the complex high stress field and high temperature field.The deformation and rheological properties of roadway surrounding rock are more obvious and the mechanism of "solid" is weakened,meanwhile,the "fluid" is enhanced,the phenomenon of solid flow transformation occurs.The main reason for the disaster is caused by the high rheological and large deformation characteristics of the soft rock for the surrounding rock in deep soft rock roadway support and the rheological and thermal damage energy dissipation of the soft rock mass is the most common problem.It is key to solve the problem is getting rules of soft rock rheology under high temperature and high pressure key.Natural soft rock is difficult to sample and their own discrete and random,so using the paraffin as a binder of the new soft rock similar materials made out the standard test object,for the study of different proportions of similar soft rock specimen physical parameters of the determination experiment,high and low temperature uniaxial failure test and high temperature creep experiment.On the basis of study and analysis the physical parameters of heat sensitivity,strength,strong creep under high temperature characteristics and the mechanism of damage,by multi-field coupling software COMSOL Multiphysics get the main conclusion:(1)Based on the similarity three theorem,the similarity theory system with temperature and seepage effect is deduced by the method of dimension method,and 18 similarity criteria are obtained with the basic mechanical parameters and thermophysical parameters as the index.the organic weakly sensitive paraffin wax as cementing agent,40 mesh river sand and iron man as aggregate for the preparation make up four kinds of similar soft rock similar to the sample.Basic mechanical parameters of four types of similarity soft match similarity criteria.Obtain the thermal conductivity,thermal diffusivity and thermal resistance of the four types of similar softrock are measured in the same principle with different temperature.The similarity criterion is used as the theoretical basis for the model experiment and for the selection& preparation of the model experiment and the design & development of the model have important guiding role;(2)Design and develop a heating and cooling(high and low temperature)environmental test box based on TAW-200 electronic multi-function material mechanical testing machine.The environment box is composed of heating system,refrigeration system,box,control system and test system.It can provide-40 ?~200 ?temperature environment for the model and can be used for rock high and low temperature uniaxial compression,shear,rheological test of various high and low temperature environment test procedures,including long time high and low temperature uniaxial creep test;(3)The experiments of four kinds of similar soft rock under different temperature uniaxial compression experiments are as follows:(1)The stress-strain curves of uniaxial compression of similar soft rock samples can be divided into four stages:compaction stage,linear elastic stage,plastic deformation stage and strain softening stage at different temperatures.besides show strong rheological properties in high temperature.(2)With the increase of temperature,the elastic modulus and peak intensity of similar soft rock gradually decrease,and the maximum value occur at low temperature of-20 ?.(3)At different temperatures,similar soft rock are in different damage forms.Between-20? and 10?,the damage form of the specimen is through,which belongs to the typical brittle failure.Between20?and 40?,the damage form is imperfect through and shear.which is between brittleness destruction and plastic damage,with obvious imperfections,the specimen damage occurs like shear failure and wedge debris damage in two forms in 50 ?,showing a strong rheological deformation characteristics.(4)The more the content of cementing paraffin,the higher the strength and elastic modulus of similar soft rock specimen.(5)The compressive strength and elastic modulus of similar soft rock show obvious loading rate effect at room temperature.In the range of 100N/s-500N/s,the compressive strength and elastic modulus increase first and then decrease.At 300N/s loading rate,compressive strength and elastic modulus are largest.(4)The results show that the four types of similar soft rock are subjected to uniaxial creep at different temperatures as follows:(1)At room temperature,the stress-strain curve of similar soft rock is linear,and the temperature has little effect on the stress-strain.With the increase of temperature,the stress-strain curve is continuously shifted upward and the temperature is higher,the shifting is larger.The average creep modulus decreases with the increase of temperature or creep time,andthe decreasing trend is especially obvious at 30 ? ~40 ?.The compaction stage occurred at room temperature,there was no obvious compaction stage in the creep process at high temperature in contrast.(2)The soft rock has three kinds of creep laws under different temperature stress: instantaneous elastic deformation and deceleration creep;instantaneous elastic deformation,deceleration creep and stable creep;instantaneous elastic deformation,deceleration creep and accelerated creep,respectively the creep equation is an exponential equation,a logarithmic equation and a power function equation.(3)At the same axial pressure and temperature,the stable creep rate of similar soft rock increases with the increase of sand ratio.(4)Introduced temperature dampers and construct the constitutive equation of soft rock nonlinear creep model with stress threshold and temperature threshold.which is very important to describe the creep law of soft rock under the coupling of temperature and pressure.(5)The mechanical properties of similar soft rock and primary rock specimen model under different temperature and confining pressure are analyzed by COMSOL Multiphysics.The simulation results can be used to verify the similarity theory.At the same time,the similar soft rock roadway model creep characteristics,the influence of temperature on similar soft rock strain curve,maximum strain energy density and maximum equivalent creep rate is obtained. |
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