Study On Bearing Characteristic Of Composite Bolt-rock Bearing Structure And Its Application In Roadway Bolting Design

Bolting support can not only play a role as suspension, composite beam andcombined arch, but also form a bearing structure with some intensity by theinteraction with the surrounding rock. But the current bolting design methods don’ttake the bearing structure into account. Based on the analysis of predecessors’achievements and by combining with the existing theoretical results of surroundingrock control, plane strain similar material simulation experiment, numericalsimulation analysis, theory analysis, calculator program and engineering practices,this dissertation put forward the theory of Composite Bolt-Rock Bearing Structure,established a mechanical model of Composite Bolt-Rock Bearing Structure ofdifferent roadway section, revealed its loading bearing mechanism and characteristic,determined its stability criterion and developed a design software. Main results are asfollows:(1) The change of stress and rock deformation around roadway of CompositeBolt-Rock Bearing Structure were as follows: In the initial stage the stress anddeformation increased slowly. In the middle stage the stress had a rapid growth topeak stress and the deformation increased rapidly with the coordinated effect of boltand surrounding rock. When the load reaches a certain degree, the stress exceeded thelimit bearing capacity and then fallen to the residual stress state due to the damage ofsurrounding rock and the deformation was accelerated development.(2) The paper put forward the concept of Composite Bolt-Rock Bearing Structure.Displacement per stress of rock deformation around roadway was one symble whichreflected the ability to resist deformation under pressure. The less displacement perstress of rock deformation around roadway was, the stronger the ability to resistdeformation of the roadway had. The simulation showed that the displacement perstress in the initial and middle stage was less than it is in the last stage, thedisplacement per stress with high support density was less than it is with low supportdensity and the displacement per stress with long bolt length was less than it is withshort bolt length. The displacement per stress with large bolt diameter was less than itis with small bolt diameter. However, when the bolt length was relatively long,increasing the bolt length had little effect on the strength of Composite Bolt-RockBearing Structure. (3) Based on different roadway section, for instance semi-circular arch andrectangle, we established a corresponding mechanical model of Composite Bolt-RockBearing Structure and obtained the formula of geometric parameter and strength. Theformula of Composite Bolt-Rock Bearing Structure strength indicated that thestrength not only associated with force condition, but also affected by geometricparameter. Based on natural equilibrium arch theory, we calculated the weight of thepotential overlying loose strata and determined stability criterion of CompositeBolt-Rock Bearing Structure.(4) By separating Composite Bolt-Rock Bearing Structure from surrounding rockand its destructive loading test, we got its destruction form of Composite Bolt-RockBearing Structure: cracks occurred in roof, roof sag increased dramatically andapplied stress was difficult to maintain stable. The correctness of the theoreticalcalculations was verified.(5) Based on the stability criterion of Composite Bolt-Rock Bearing Structure,we established design procedure of bolt support parameters initially and developeddesign software of roadway bolting support with a computer program. The resultsdesigned by this design software were applied successfully in three field tests ofGucheng coal mine, Dan Shuigou coal mine and Huale coal mine under typicalgeological conditions of roadway. The application results showed that the bolt supportparameters designed based on Composite Bolt-Rock Bearing Structure controlled ofthe deformation of roadway effectively and the research results of paper werevertifyed to be sicence and reliability from the engineering practice.