Research On In-situ Test Theory And Evaluation Method Of Surrounding Rock Based On The Digital Drilling In Mine Roadway

Coal is the pillar energy in China,and it has the function of ballast for energy safety.The artery of coal mine is the roadway,the stability of which restricts the safety and efficiency of the coal mine production.What’s more,the effective support of surrounding rock is an important guarantee for the safety and stability control of the roadway,and the premise is the real-time testing and quantitative evaluation of the mechanical parameters and structural characteristics of the surrounding rock.However,the traditional laboratory rock testing method is complicated and has a long period,so it is difficult to test the surrounding rock properties in true state.Especially for the broken surrounding rock which needs to be strengthened,it is difficult to take the core effectively for testing.Meanwhile,it is difficult to test the mechanical parameters and structural characteristics of the surrounding rock in situ.The evaluation of the effect of bolt grouting support is mainly qualitative evaluation,which makes the design of deep broken surrounding rock lack of quantitative index support,with large experience and lagging support design optimization.Therefore,it is one of the fundamental reasons for the frequent safety accidents of broken surrounding rock.How to realize in-situ real-time testing and quantitative evaluation of surrounding rock mechanical parameters and structural characteristics is a theoretical and technical problem for mine roadway safety control.Digital drilling test is a technology that uses digital drilling equipment to control,monitor and analyze rock drilling parameters.The studies have shown that the drilling parameters are related to the rock strength parameters and structural characteristics.Therefore,digital drilling test technology provides a new way for in-situ real-time testing and quantitative evaluation of roadway surrounding rock.The establishment of rock drilling inversion model and method and the development of test equipment are the core of real-time acquisition of roadway surrounding rock parameters and quantitative evaluation of support effect based on drilling.In addition,it is also the key scientific and engineering problems.In the past,the statistical and empirical analysis methods are mainly used to study the relationship between single type drilling parameters of drill bit with complex structure and rock parameters.No researches on in-situ testing and evaluation method of surrounding rock of mine roadway based on digital drilling have been reported.Based on this,this paper adopts the methods of theoretical analysis,laboratory test,equipment development and field test to carry out the research on digital drilling in-situ testing theory and evaluation method of mine roadway surrounding rock,and the effectiveness of the surrounding rock mechanical parameters in-situ measurement,rock interface identification,fracture range detection and quantitative evaluation of bolt-grouting effect based on digital drilling is proved,so as to provide theoretical and technical support for drilling real-time acquisition of basic parameters of roadway surrounding rock safety control and support design.The main research work and results are as follows:(1)Research on drilling inversion model of rock mechanics parametersThe digital drilling analytical bit is designed and developed.Based on the energy analysis and upper bound method,the theoretical solutions of rock cutting energy and rock cutting strength of the analytical drilling bit are obtained.The rock UCS drilling inversion model(CDP-UCS model)and rock c-φ drilling inversion model(CDP-cφ model)are established,which integrate four kinds of drilling parameters.Besides,compared with the DP-UCS model and DP-cφ model derived based on the solid analytical drilling bit,and the theoretical response mechanism between drilling parameters and rock mechanics parameters is clarified,which shows the theoretical feasibility of effectively inversion of rock mechanics parameters using digital drilling parameters of analytical drilling bit.(2)Laboratory test study on rock digital drillingThe digital drilling tests of intact rock,layered rock and grouting rock are carried out by using multifunctional rock mass digital drilling test system(TRD system in laboratory),so that the response laws of drilling parameters to rock mechanical parameters,rock interface,fracture range and other rock structure characteristics are analyzed.In addition,the variation laws of drilling parameters,cutting energy and cutting strength under different water cement ratio and rock fracture degree are obtained.The drilling torque,cutting energy and cutting strength of rock increase with the increase of rock strength,which is consistent with the theoretical response of drilling parameters to rock mechanics parameters.What’s more,the correctness of rock mechanics parameters drilling inversion model is verified,and the feasibility of rock interface identification,detection of surrounding rock fracture range and quantitative evaluation of rock mass grouting effect by using drilling parameters of analytical drilling bit is proved.(3)Development of surrounding rock digital drilling in-situ test systemThe surrounding rock digital drilling in-situ test system of mine roadway(Site SDT system)is developed,which is composed of steering drilling subsystem,hydraulic servo subsystem,monitoring and control subsystem,test assistant subsystem.It can realize surrounding rock in-situ digital drilling test of underground engineering such as mine roadway.Besides,the digital drilling analytic bit and the control range of drilling parameters adopted by this system are the same as those of the TRD system in laboratory,and match with the drilling inversion model of rock mechanics parameters.The research conclusions of the TRD system in laboratory can provide effective theoretical and data support for the engineering application of the site SDT system.On this basis,the method of drilling testing and zoning of roadway surrounding rock mechanical parameters,the method of drilling testing the roadway surrounding rock structural characteristics,and the method of drilling evaluating the bolt-grouting effect of roadway surrounding rock are established.(4)Research on indoor verification test of site SDT systemThe indoor digital drilling test of rock mass with different combination rock mass layers,such as intact rock layer,broken rock mass layer and grouting rock mass layer,is carried out by using the site SDT system,and the site SDT system has good control and monitoring performance.The response of drilling parameters at the rock interface is obvious,and the average difference rate between the equivalent rock mechanics parameters tested based on the site SDT system and the indoor compression test results is less than 15%,so the site SDT system has the feasibility and effectiveness of identifying the rock interface and testing the rock equivalent mechanical parameters.Additionally,the equivalent compressive strength of the fractured rock mass after grouting tested based on the site SDT system is 3.5 times that before grouting,and 30.3%lower than the intact rock.The site SDT system has the feasibility and effectiveness of quantitatively evaluating the grouting reinforcement effect of the broken rock mass.(5)In-situ test and evaluation of deep surrounding rock based on digital drillingBased on the site SDT system and the in-situ digital drilling test and evaluation method of roadway surrounding rock,taking Wanfu Coal Mine,the deep mine with high stress and thick alluvium,as the engineering background,the surrounding rock digital drilling test,borehole peeping and coring test are carried out.The rock mass structure characteristics such as rock fracture,rock layer interface and fracture range are obtained.According to the equivalent strength,the surrounding rock of chamber can be divided into strength deterioration area,strength recovery area and original rock strength area.On this basis,the bolt-grouting reinforcement scheme design and digital drilling in-situ evaluation of the chamber surrounding rock are carried out.The average equivalent strength increase rate of the broken area of surrounding rock after reinforced by bolt-grouting is 61.6%.Therefore,the in-situ testing and evaluation method of roadway surrounding rock based on digital drilling has the advantages of fast testing drilling parameters and continuous obtaining rock equivalent strength,which provides an effective mean for surrounding rock strength zoning and support design optimization.