| With the increase of mining depth,more and more coal mines have entered the deep mining stage.Floor heave have appeared at different level in many roadways,which has seriously affected the life property safety of people and the efficient production of coal mines,is an urgent engineering problem to be solved.However,due to the complicated and variable conditions of the deep rock mass,accompany with the high geostress,high geothermal,the hyperosmosis and the disturbance,the deformation and failure mechanism of floor heave is extremely complicated.In order to control the floor heave in the deep soft rock roadway and put forward a scientific and rational control measure,it is necessary to carry out relevant research work on the deformation and failure of the floor heave and master its mechanism.Most deep soft rock roadways are in sedimentary rock stratum and the impact of rock stratum structure on roadway surrounding rock can't be ignored,so the rock structure should be considered and the deformation and failure of roadway in layered rock mass should be under research when comes into the problems of floor heave.The thesis aimed to research the floor heave of soft rock roadway in slowly inclined stratified rock mass.The structure and the stress characteristics of the floor of the layered rock roadway were researched theoretically.A mechanical model of the floor rock beam of the slowly inclined layered soft rock roadway was built.The flexural rigidity of the floor rock beam,the critical deflection and the critical load of the flexure failure were analyzed.The main controlling factors of the floor heave of gently inclined layered soft rock were analyzed,the stress distribution and the law of instability slip were summarized,and the floor heave mechanism of the soft rock roadway in the layered rock was revealed.Taking different deep soft rock laneways as the engineering background,the physical model experiment on the floor heave of deep well soft rock roadway under different rock mass structure conditions were carried out.With the help of digital image related technology,infrared thermal imaging technology and strain measurement element,the data of stress field,temperature field and displacement field obtained from the experiment are obtained.The stress conditions and key positions of floor heave in layered rock roadway with different structural characteristics were determined,and the abnormal temperature changes before the failure of the floor rock strata were obtained,and the deformation and evolution law of the surrounding rock in the roadway was revealed.At the same time,the 3DEC discrete element numerical simulation software is used to simulate the floor heave of the soft rock roadway with different rock strata and different roadway sections,and the effect of the structure effect of the rock layer on the floor heave of the roadway is studied.The experimental results of the physical model experiments of thin layer soft rock circular roadway and thin layer straight wall semi-circular arch tunnel are analyzed,and conclusions are drew the following:(1)When the lateral pressure coefficient was relatively small,the deformation of surrounding was small and the floor heave failure will not happen.During the process of the side pressure coefficient increased,when the lateral pressure coefficient reached a certain threshold,the bottom heave failure will happen.In the process of floor heave,the deformation of surrounding rock appears the symmetrical features.The displacement deformation of roadway's two sides and floor is relatively large,and displacement of roof deformation is relatively small;(2)The failure key position was at the right corner of the roadway for the thin layer soft rock circular roadway.The process of the floor heave was that,firstly floor strata took dislocation,then floor stratum separated from the adjacent stratum,next the floor strata was fractured and moved toward the face of roadway,finally the roadway took serious floor heave;(3)The failure key position was at the right corner of the roadway for thin layer straight wall semi-circular arch tunnel.The process of the floor heave was that,firstly floor strata produced flexural deformation.With the increase of the flexural deformation of floor strata,the stratum separated from the adjacent stratum.And then tthe upper part of the floor is fractured,and the other strata are uplifted along the bottom plate of the fracture,finally the roadway took serious floor heave;(4)Process of destruction of surrounding rock is accompanied by abnormal temperature change.The temperature reducing area can reflect the produce of cracks or the decrease of stress state of the rock mass.At the same time,the temperature increase area can reflect the rock in this area happen to friction rupture.The range of temperature anomalies of surrounding rock can represent the damage range of surrounding rock of roadway,so the temperature characteristics of the rock mass can represent the mechanical behavior of rock mass to a certain extent;(5)After the roadway was damaged by floor heave,surrounding rock is in the state of tensile stress,and the rock mass in the far side is in the state of compressive stress.The roadway was destroyed under the combined action of the tension and the compressive pressure.Based on the analysis of the experimental results of the physical model experiment of the thick layer straight wall semi-circular arch tunnel,the following conclusions are drawn:(1)To deep soft layered rock roadway,when the floor is thickness soft rock,the surrounding rock can present large displacement,the deformation of the floor is more than two sides' and roof's deformation,and appears a slight floor heave;(2)The stress state of surrounding rock is affected by the excavation of roadway which can't be ignored.With the increase of excavation footage,the tensile stress increases in the left and right corner of the roadway,then the tensile stress increases at the top of the roadway,as well as rock in the far side of right corner.A double hole diameter dimension of the surrounding rock of the roadway were in the tensile stress state;(3)The decrease of surrounding rock temperature was due to the thermo elastic effect of rock mass,the reduce stress of rock mass reduced in the roadway excavation,and the negative change of temperature caused by thermo elastic effect,during the first six steps.The production of micro cracks causes a decrease in temperature during the latter two steps.The rising temperature of rock strata in the roadway excavation is caused by the friction in the floor rock strata,which accumulates the energy to raise the temperature.The characteristics of the temperature change of surrounding rock can characterize the mechanical deformation behavior of roadway surrounding rock to a certain extent;The discrete element numerical simulation software 3DEC is used to simulate the floor heave of soft rock roadway with different section shape,different rock dip angle and different rock thickness.The deformation and failure characteristics of roadway surrounding rock,the key position of the floor heave of the roadway,the stress evolution process of roadway surrounding rock and the migration process of floor stratum are also researched under different rock structure conditions.Based on the above study,the following main conclusions are drawn:(1)For the soft roadway which are located in the deep slowly inclined stratum,the displacement and deformation of the surrounding rock are greatly different under the condition that the other rock structure conditions are the same except the tunnel section,and the shape of the tunnel section has a great influence on the floor heave of the roadway.When the shape of the roadway changed from round to straight wall arches or square,the deformation of the floor is obviously increased,and the key position of the floor heave of soft rock roadway with different cross-section shape is located in the right bottom corner of the roadway;(2)For the soft roadway which are located in the deep slowly inclined stratum,With the increase of the dip angle of the strata(in the range of 0 to 30 degrees),the deformation of the floor increased gradually under the condition that the other rock structure conditions are the same except the strata inclination.The surrounding rock of the roadway is not symmetrical,and the deformation and failure of the floor heave is more obvious.The key position of the damage is increased from the middle position of the roadway floor to the position which is near the bedding plane;(3)For the soft roadway which are located in the deep slowly inclined stratum,The deformation of roadway surrounding rock decreases with the increase of rock thickness.When the thickness of rock reaches a certain value,the influence of rock thickness on roadway surrounding rock is relatively small;(4)For the soft roadway which are located in the deep slowly inclined stratum,the process of roadway floor heave is that floor stratum produced upwards deflection deformation and separated from below floor stratum under the effect of horizontal stress.With the increase of deflection,the fracture of floor rock is broken.The stratum below the floor stratum also produced upwards deflection deformation under the effect of horizontal stress which caused serious floor heave;(5)During the process of floor heave of soft rock roadway which are located in deep slowly inclined stratum,with the deformation increasing of the roadway,the stress redistribution of the surrounding rock made the tensile stress zone appear in the floor of the roadway,and the floor heave happened because of the combined action of tension and pressure stress. |
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