A mineral-strength conversion model based on LIBS technology and rapid batch testing and application of uniaxial compressive strength

ZHANG Qinghe; WANG Xiaorui; WANG Chuanbing; LI Weiguo; GONG Fengqiang; ZHANG Xinsheng; LI Jingguo

doi:10.13225/j.cnki.jccs.XH24.1480

Abstract：Due to the complexity and abruptness of deep engineering disasters,the mechanical parameters of rocks,partic-ularly uniaxial compressive strength(UCS),play a critical role in stability analysis,risk assessment,support parameter op-timization,and intelligent construction.Achieving rapid quantitative characterization of rock strength is therefore essen-tial.A novel approach for the rapid quantitative characterization of rock UCS from a mineralogical perspective is pro-posed,utilizing laser-induced breakdown spectroscopy(LIBS)technology,thereby introducing a mineral-to-strength con-version methodology.A spectral database for granite and metamorphic sandstone is constructed using LIBS,and the ele-mental and mineral datasets of the rocks are acquired by X-ray fluorescence(XRF)and X-ray diffraction(XRD)tests,re-spectively.The mass fraction of mineral components is analyzed via the support vector regression(SVR)algorithm.In the end,a mineral-strength conversion model is established to calculate the UCS from the predicted values of mineral com-ponent concentrations,and its rationality and scientific validity are validated by the standard mechanical tests.Results in-dicate that the coefficient of determination R2 of each element in the spectral-elemental prediction model is between 0.96 and 0.99,and the model can effectively obtain the content of each element;the elemental-mineral prediction model has the best prediction effect of quartz and aluminum phosphate,followed by feldspathic and mica mineral groups,and good pre-diction effect of chlorite and turbidite zeolite as well.The multiple linear regression model(R2=0.850 2)is more suitable than the least squares method(R2=0.719 6)for the nonlinear relationship between the predicted value of mineral mass fraction and uniaxial compressive strength,and the introduction of the correction coefficients can be more effective in real-izing the accurate conversion of minerals-strengths.Finally,the mineral-strength conversion model is used to conduct rap-id batch testing of the UCS of rocks in different mileage of working faces at the project site,and combined with the Kri-ging interpolation technique and Matlab technology to realize the 3D continuous visualization of the UCS at the project site.