Study On The Control Effect Of Hollow Grouting Anchor On Deep Soft Rock Tunne

With the advancement of mining to the deep,the deep roadway is faced with the problem of dynamic disasters induced by high ground stress and weak surrounding rock.After the excavation of the roadway,it is characterized by serious deformation,long deformation duration and poor stability.the mine disasters can competitively be reduced by Reasonable support of deep soft rock roadway.Hollow grouting bolt combines grouting technology with anchoring,which can rein in the surrounding rock in deep soft rock roadway occurs deformation effectively.Therefore,it is of great significance to study the optimization of hollow grouting bolt support scheme in deep soft rock roadway.In this paper,taking Jinfeng Gold Mine as the research background,the control effect of hollow grouting anchor on deep soft rock roadway is studied through the theoretical analysis,physical test,numerical modelling and on-site monitoring.The main research results are as follows:（1）The field survey indicates that under the action of high ground stress in the research area has the features of fast deformation and failure,large deformation and long duration.Through statistical analysis of field data,the RQD value is mainly concentrated in 27%～38%,the rock mass quality is’bad’grade,the whole surrounding rock is broken and has worse stability.The original pipe seam bolt support strength is low,which leads to large deformation of roadway side and roof and floor,and it is difficult to ensure the stability of roadway.（2）The theoretical analysis of Mohr Coulomb shows that the grouting improves the anchoring performance of the bolt,increases the cohesion and internal friction angle of the rock mass;the field pull-out test results show that the ultimate pull-out force of the hollow grouting anchor is 178.96 kN,and the ultimate pull-out force of the pipe joint anchor is 108.58 kN.Through calculation,the ultimate shear strength of the hollow grouting bolt anchorage layer is 3.72 MPa,which is greater than that of the pipe joint bolt.The above research shows that the overall anchoring performance of hollow grouting bolt is better than that of pipe joint bolt.（3）Combined with the numerical speckle measurement method,the similar simulation test of hollow grouting bolt support was conducted,and the displacement variation field of the monitoring points on the two sides of the roadway and the evolution characteristics of the horizontal strain field of the model under different bolt lengths and row spacing were studied.The results show that the maximum displacement and strain concentration area of the monitoring points under bolt support are smaller than those without bolt support.Based on the similarity ratio conversion,when the bolt length is 1800 mm,the maximum horizontal displacement and horizontal strain concentration area of the monitoring point are the smallest.When the row spacing between the bolts is 900 mm,the support efficiency of the bolts is higher,and the deformation of the surrounding rock of the roadway can be effectively controlled.（4）As per the FLAC^3D numerical simulation,the supporting effect of various supporting parameters of hollow grouting bolt is studied.The results show that under the original supporting parameters,the plastic failure range of pipe joint bolt roadway is wide.After optimizing the parameters of hollow grouting bolt,the maximum displacement of the two sides is 174 mm,and the maximum displacement of the roof and floor is 144 mm,which is 51.10%and 23.90%lower than the original support respectively.The maximum vertical stress and plastic zone volume of roadway are reduced by 13.20%and 59.12%compared with the original supporting,and the plastic region is patently decreased.（5）Through the field application of hollow grouting bolt and the monitoring of the rock displacement and bolt stress,the results showed that the maximum roof-to-floor reduces by 41.60%and the maximum two-side reduces by 59.60%after support optimization,and the surrounding rock reaches stability in a shorter time.The axial force of the bolt in the roadway is on the rise,and the utilization rate of the bolt is obviously increased.The hollow grouting bolt can effectively control the deformation of the surrounding rock.The research results provide support technical reference for the stability of similar engineering roadways.