Study On The Adaptability Of Anchor Plate And Its Mechanical Properties Relationships With Rock Bolt Body In Underground Engineering

Over the past 10 years,the number of underground constructions in China has increased rapidly,entering a stage of rapid development.Bolt support has been widely used in the field of underground engineering because of its convenient construction,low cost and strong environmental adaptability,becoming an indispensable part of it.However,there is no theoretical basis for the selection of anchor plate in construction at present.This may lead to large deformation of the anchor plate in severe environment.It is also very difficult to detect the force of anchorage system.At home and abroad,most of the researches on anchorage system focus on the bolt body itself.The stress condition of the anchor plate is seldom studied.The relationship between the anchor plate and the bolt body is rarely involved.Knowing the stress condition of the anchor plate and the bolt body quickly,accurately,conveniently and establishing the relationship between them,which can help to quickly determine the mechanical properties of the bolt body according to the stress characteristics of the anchor plate,can provide technical references for the loading effect of prestressed anchor bolt.The research results are of great scientific significance and engineering value.In this paper,the anchor plate and the bolt body are the main research objects.Based on the fiber bragg grating sensing technology,laboratory tests were carried out,revealing the adaptability of the anchor plate and the mechanical relationship with the bolt body under different working conditions.The main results are as follows:(1)The influence of different anchorage forms(fixing by expansion shell and fixing by nut)on the axial force of rock bolt is revealed through tests.There is no significant difference between them.With the change of applied load,the axial force of the rock bolt and the stress of the anchor plate are linear change,proving the feasibility of using fiber bragg grating sensors to measure axial force of the rock bolt and the stress of the anchor plate.(2)The basic stress characteristics of the rock bolt are proved by the tests: The axial forces along the rock bolt are almost equal.The test results show that the greater the applied loads are,the greater the axial forces of the rock bolt will be.However,the axial forces of the rock bolt are not equal to the applied load,but showing a multiple relationship.When the applied load is greater than 10 kN and less than 40 kN,the applied load is approximately 0.66 times the axial force of the rock bolt.(3)Through the tests,it is revealed that the effect of the bowl shaped anchor plate and plate shaped anchor plate are almost the same in anchorage system,which shows that the shape of the anchor plate has no obvious effect on the axial force of the rock bolt under hard rock conditions.(4)The mechanical relationships between the anchor plate and the rock bolt body under vertical and non vertical conditions are revealed by tests: In the presence of the dome washer,the stress of the anchor plate and the axial force of the rock bolt are almost linear change.When the inclination angle is less than 20 degrees,the change of it has no obvious effect on the relationships between the anchor plate and rock bolt body,which means the change of the inclination angle has little effect on the stress of anchor plate and the axial force of the rock bolt.(5)When the inclination angle is less than 20 degrees,the change of it has no obvious effect on the axial force of the rock bolt body and the stress of the anchor plate.Different pull out methods have no effect on axial force of rock bolt body.(6)The tests reveal that without the dome washer,the greater the applied load is,the greater the bending moment of the rock bolt will be,which may lead to the permanent deformation of the rock bolt.Without the dome washer,the maximum axial forces of the rock bolt and the stresses of the anchor plate are greater than those of the rock bolt with dome washer under different working conditions and the change of the inclination angle has a great influence on the mechanical properties of the anchor plate and rock bolt body,revealing the utility of the dome washer in anchorage system.