| For a long time,the support problem of t he deep soft rock tunnel has been a problem for t he construction of the coal mine in China.The mechanical reasons for the instability of this kind of roadway support are complex,and the main mechanisms are weak lithology,dynamic pressure of excavation,broken structure,hydrolytic softening and so on.Especially the roadway rich in montmorillonite surrounding rock is the most difficult.Due to the common phenomenon,such as the poor anchoring,small grouting range and large softening coefficient,the conventional supporting method is not effective,and a large amount of manpower and material resources are consumed,and the normal development of deep resources is hindered.Through the theoretical calculation,the experimental test and the engineering practice,the cooperative loadbearing efficiency and the dynamic construction process of the multi-layer anchor rod,the bottom angle pressure relief and the graded grouting are studied.The main results are as follows:1)SEM,EDS and XRD s how that the total amount of clay minerals content is 42%～79%,which montmorillonite content is 69%～97%,there are a large number of pores,cracks and nanoscale and micron layer gaps.The triaxial test shows that the fracture expansion of surrounding rock under mining disturbance aggravates the weakening of lithology.When the depth of fragmentation breaks through the anchoring range,the support strength decreases continuously,and finally the support at all levels will be gradually unstable,which is the fundamental mechanical mechanism of the failure of this kind of roadway.2)The multi-level bolting and unloading support technology was simulated by ANSYS and FLAC3 D,which shows that the roof subsidence is less than 170 mm,the bottom bulge is less than 210 mm,the bolt force is uniform,the stress in the pressure relief area is reduced by 43%,and the displacement of the bottom plate is reduced by 74%.3)In order to study the pressure relief mechanism,a small similar roadway test block was made.The research shows that the pressure relief groove accelerates the stress redistribution,which can stimulate the tensile fracture,fracturing gap and shear fracture.The rock fracture near the roadway is characterized by large size and small number,which is beneficial to the formation and strengthening of rock structure and anchor bearing arch structure.4)The typical roadway is selected for engineering application,and the reinforcement scheme of bottom angle pressure relief groove and embedded bolt secondary grouting is implemented,the grouting time is optimized,the dynamic unity of structural pressure reduction and surrounding rock modification is realized,and a set of multi-level anchor,unloading and grouting support te chnology suitable for montmorillonite surrounding rock roadway is formed.Figure 46;Table 4;Reference 57... |
