| Coal, the main energy of our country, plays a decisive role in our nationaleconomy. The support technology of mining gateway is regarded as a key link of coalmine production. So, how to reduce cost and raise efficiency is an important issuewhich we are confronted. Nowadays80percent of large-scale mines are coalroadway. With the increase of mining intensity and mechanization degree for coalmine in our country, the roadway section which is required by fully mechanizedtop-coal caving method in thick coal seam and the fully mechanized single minefull-height method become large and large,. Moreover, with the improvement ofcoal mining technology, the supporting problem of high stressed soft rock roadway isbecoming more and more outstanding. In recent years, the bolt-mesh-cable supportingtechnology has been the main method in roadway of large section. As this method haslarge supporting strength, low cost and a number of other advantages, the applicationof bolt-mesh-cable provide an effective approach to solve large section gatewaysupporting problems. However, pre-stressed bolt-mesh-cable theoretical research wasfar behind the engineering practice. Especially, the deformation characteristics forcombined support of pre-stressed anchor and anchor rope in high stressed soft rockroadway has not been reported. Therefore, with the support problem of Malin coalmine C8seam gateway as the background, aiming at the rheological problem of highstressed soft rock roadway, the study of surrounding rock deformation features andfailure mechanism was carried out in this paper. The rheological constitutive modelsof roadway bolt and surrounding rock was established by rheological test. UsingFLAC3D numerical simulation software, the deformation mechanism of high stresssoft rock roadway under different pre-tightening force of anchor and anchor rope wasstudied, and the results were applied to the high stress roadway supporting system.The following innovative studied results were obtained：1）Based on the result of argillaceous siltstone conventional triaxial compressiontest, the post-peak strain softening characteristic of argillaceous siltstone at differentconfining stress was studied by establishing the mechanical model of post-peaksoftening soft rock at different confining stress. The soft rock subsequent yield surface model was characterized by the generalized cohesion(c) and the generalizedinternal friction angle(). Besides, the generalized cohesion(c) and the generalizedinternal friction angle() at different equivalent plastic shear strain(εps) anddifferent confining stress were determined by Mohr’s stress circle.2) According to the law curve and time-dependent properties, which had beenobtained by the soft rock graduation loading triaxial compression creep test, Burgersviscoelasticity rheologic model of argillaceous siltstone at high-stress situation wasestablished. On the basis of viscoelastic plasticity mechanics theory, theone-dimensional creep constitutive equation this model was derived, and than themodel parameters were identified with the help of non-line regression. By analyzingthe surrounding rock rheological properties of roadway, the viscoelastic solution ofsurrounding rock displacement was obtained, and the relationship among thesurrounding rock deformation and stress, roadway radius, rock characteristics andsupporting system was studied.3) Using Monte-Carlo generating random number method to simulate thestructural plane of gateway with network, the rock mass quality was estimated.Furthermore, on the basis of this mehcod, the rock mechanics parameters estimationmethod of gateway was proposed, and the suggested values for gateway rockmechanics parameters were given.4) By establishing the three-dimensional rheological constitutive model ofbolt-cable combination support for high stressed soft rock roadway, the mechanism ofaction for pre-stressed bolt-cable and surrounding rock was analyzed. Thedisplacement field and stress field in high-stress soft rock gateway were simulated byfinite difference numerical software FLAC3D. The stress field distribution featurescaused by different pre-stress combination which was exerted by bolt or bolt-cable atsoft rock roadway under the condition of high vertical stress and horizontal stress wasstudied. The rock stress field distribution features of roadway at different distanceamong bolts was also studied, and the law of surrounding rock deformation and stresschanged with time was given.5)The control action at different support intensity for the high stress soft rockroadway was studied using numerical simulation. The result shows that the initialdeformation of high stress soft rock roadway was insurmountable. So the "yield pressure support" is proposed. The yield pressure support mechanics model wasestablished, and the support effects influenced by different yield distance anddifferentlimited deformation amount was analyzed.6) The idea of the secondary load bearing layer which was constructed by thecompound arch composed of bolt-cable combination support was proposed. Moreover,the coordination of prestressing force for bolt-cable combination support wasproposed. The parameter optimization of bolt-cable combination support for highstressed soft rock roadway was achieved. The research results indicate that: Thegenerated compressive zone of bolts group support should connect and overlap to awhole and than made up the arch structure which function was to sustain the roofmust be guaranteed by rational supporting density. Bolts’ length was an element tomake the secondary bearing stratum steadiness. When supporting density was fixed,the increase of the bolt length will not affect the bolt supporting effect, and the boltslength only required to satisfied the thickness of compound arch which forms atroadway roof.7) Aiming at the existent problems of high-stress soft rock gateway supportingtechnology, the research achievements was applied to2083gateway of Malin colliery.Through made field measurement, the gateway surrounding rock deformation andcreep were controlled by this supporting system effectively, and the roadway stabilityincreased sharply. |
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