Study On Testing Methods Of Rock Mechanics Parameters Based On Digital Drilling Testing Technology

In recent years,the construction speed and construction scale of underground engineering in China have been developed unprecedentedly.The corresponding complex conditions of underground engineering are increasing year by year,which have caused great challenge to the stability control of surrounding rock and construction safety.The rapid and effective prediction of the surrounding rock mass structure and mechanical parameters on site is a prerequisite for rational support design of underground engineering and guarantees the safe and efficient construction of underground projects.Therefore,it is particularly important to develop a method for rapid and effective measurement of rock mechanics parameters.The existing methods for testing rock mechanics parameters such as uniaxial compressive strength(UCS),cohesive force c,and internal friction angle ? of rock,are tedious in process,long period,high cost,test lag,and limitation of application range.Therefore,it is urgent to establish a method for rapid and effective prediction of rock mass structure and mechanical parameters on site.Based on this,this article around the rapid measurement method of rock mechanics parameters,through mechanical analysis and mathematical statistics methods,combined with indoor rock drilling test to carry out related research,and achieved the following results:(1)Correlation studies between drilling parameters and between drilling parameters and rock mechanics parametersA multi-function digital drilling test system was developed independently and a new type of polycrystalline diamond compact drill bit was developed.The drilling test of granite,limestone,sandstone and mortar specimens was carried out.The correlation between drilling parameters and between drilling parameters and rock mechanics parameters was revealed.The rationality and effectiveness of the digital drilling test system structure are verified.In the rock drilling process,there is a significant correlation between the drillingparameters and between the drilling parameters and the rock mechanics parameters.With the increase of drilling speed,the drilling torque and drilling pressure show a nonlinear increasing trend,and the increasing speed gradually increases.With the increase of rotational speed,the drilling torque and the drilling pressure show a gradually decreasing trend of nonlinear change,and the decrease speed is obviously reduced.(2)Test method of rock UCS based on digital drillingThe rock unit cutting energy was derived by energy analysis.Based on the digital drilling test system,rock drilling test and uniaxial compression test were carried out,and the drilling parameters and mechanics parameters of rock samples with different strength were obtained.On this basis,the relationship model between drilling parameters and UCS was established by using SVM method.The performance of relationship model between drilling parameters and UCS was evaluated by digital drilling test.The comparative analysis of rock drilling test and uniaxial compression test shows that the UCS predicted by the relationship model is close to the UCS measured by uniaxial compression test,with R2 being 0.9831 and MAE being 2.772 MPa.It is proved that the relationship model between drilling parameters and UCS based on SVM method has achieved good results in the UCS prediction of rock mass,and also provide a new idea for establishing a universal relationship model between the drilling parameters and UCS.(3)Test method of rock c-? parameters based on digital drillingConsidering the rock cutting damage characteristics,an mechanical model for rock cutting upper bound analysis is proposed.Based on the principle of virtual work,the ultimate cutting force of rock is derived,and the relationship between the drilling parameters and the c-(p parameter of rock is established.The drilling tests of limestone samples under different schemes were carried out,and the drilling parameters and corresponding parameters of theoretical calculation were compared and analyzed.The average difference rate of limestone schemes is less than 10%,which verifies the rationality and effectiveness of the relationship between drilling parameters and rock c-? parameters.Combining the rock UCS digital drilling prediction method,a digital drilling determination method for rock c-? parameters is proposed.The comparative analysis of the rock mechanics parameters determined by the digital drill method and the traditional triaxial compression test method.It proves the validity and feasibility of the proposed method for rapid determination of rock mechanics parameters based on digital drilling.