| Aimed at the control technology of prestress anchoring in mine entry, there takeda systematic research on the transformational mechanism of initial anchoring forceand pre-tightening torque by the comprehensive research of experiment, fieldobservation, mechanical analysis model and numerical calculation etc. there alsoanalyzed the fluctuate evolution law and factors for the anchoring force during theperiod of extraction, and put forward the theory of critical pretightening torque.What’s more, this dissertation revealed the evaluation law of anchoring force duringthe surrounding rock’s destruction and the theory of synergistic bearing, theseachievement innovate the technical method for stabilizing anchoring force,engineering practice also been taken into this research and the main conclusions are asfollows.(1) Analyzed the transformational relationship between bolt’s lift anchoring forceand pre-tightening torque, the stress distribution and factors of lift anchoring force inthe bolt’s axial direction also been taken into consideration. Get the conclusion thattorque coefficient tends to be a constant value and the concept of pre-tighteningtorque was put forward, which can be demonstrated by testing the conversion betweendifferent lift anchoring force and pre-tightening torque, the experiment based on theintegrated testing bench with prestressed anchor system and three kinds ofengineering interfaces such as layered rock surface, rough coal face and smoothinterface after shotcrete.(2) Based on analysis to bond stress and mechanical transmission in theanchoring segment of strata rock mass, this dissertation amended shearing hystereticmodel, and explained the phenomenon of debonding seriatim and iterated destroy instrata rock mass, then proposed the criterion for taking off anchoring seriatim andrevealed the mechanism of fluctuant vibration in lift anchoring force.(3) Measured the roof’s lift anchoring force of bolts (62groups) and cables (47groups) in7deep-mine roadways, and summarized the basic laws of the fluctuation inlift anchoring force, concluded that the fluctuation in lift anchoring force can beinfluenced by several factors such as strata numbers, initial pretightening force,mining-induced stress and stiffness of the surface supporting component etc.. Sumedthe working lift anchoring force up in eight types during the overall period ofexcavation and mining, there are stable type, zooming first and then tend to be stable,sole increasing types, sole slow descent type, slow falling first and then tend to be stable, zigzag vibration and step down type etc., among all of these types, the lastthree types aren’t beneficial to the stable and safety of surrounding rock while theothers are.(4) By making a survey on the bolt supporting roadway in several mines, thisdissertation analyzed the relationship between the loss of lift anchoring force and thedamage of surrounding rock, summed up the reason of complete loss in lift anchoringforce, partial loss and no loss, which are corresponding to supporting failure,inefficient and large deformation of the roadway respectively. Combined withnumerical calculation software FLAC3D, reasonable value of pretightening force wasanalyzed too. Then presented the synergistic bearing system that can eliminate thetensile stress in bolt’s tail end by using high pretightening cable and surfacesupporting component with high stiffness. Bonding property and anchoring length ofanchoring agent also been taken into consideration.(5) Based on the theory of synergistic bearing, there formed the technology ofcontrolling bolt’s anchorage force with secular stability by creating products withhomogeneous bearing capacity such as dishing cable tray, ribbed high-strength&bending-resistant steel belt shaped like T, composite steel belt with high strength andflexible bolt’s locking structure.Better social and economic benefits can be acquired by putting aboveconclusions into practice such as tail entry’s gob-side entry retaining of first miningface1252(1) in Pan yi-dong mine, tail entry’s gob-side entry driving with coal pillarretaining of face1252(1) in Dingji mine, reinforcement for ingate of mixing shaftunder level-1050in Kongzhuang mine, the first two mines belonged to HuainanMining Group while the last one to Datun mining area.There are93figures,20tables and191references in this dissertation. |
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