A Method Of Situ-stress Estimation: Rock-mass Hydraulic Fracturing

Situ-stress is the fundamental force that cause the deformation and failure in miningand other underground or open-air geotechnical excavation engineering. Situ-stressmeasurement is prerequisite to determine mechanics properties of the engineeringrock-mass and analysis stability of adjacent rock stability.Situ-stress measurement isprerequisite to realize scientific design and decision making in engineering rock-mass. Butthe application of situ-stress measurement in underground engineering design are rare.Situ-stress measurement have not form a system method in theory or practice. Therefore,this paper has carried out an in-depth research on situ-stress estimation by hydraulicfracturing in rock mass.Firstly,the use of hydraulic fracturing true triaxial hydraulic fracturing experiment system for hydraulic fracturing stress measurement validation experiments, drawing that the system can be well simulated hydraulic fracturing stress measurement; the accuracy rate of closing pressure is determined at90%; conventional methods to calculate the stress value isnot considered rock permeability, calculation accuracy rate to be improved.Secondly，Through the analysis of formula H-W、H-F and rock permeability，built arock fracture pressure of the comprehensive calculation formula.Using experimentalfracture pressure inferred the test block of rock contact porosity and elastic core constant.Verifing formula through the new experiment，the experimental results showed thatformula considering the permeability of the rock compute make horizontal geostress valuescompute up to93%.Again, on the basis of conventional hydraulic crack technology, application of in-situstress calculation formula that has been derived, increase hole packer of hydraulicfracturing, heavy sheets fracturing process steps to increase pressure-shut off the pumpand water pressure determination, forming a complete process of situ-stress estimation byhydraulic fracturing in engineering rock mass.Finally, Measurement Verification and Application apply process of situ-stressestimation by hydraulic fracturing in the coalbed methane well pressure well testing， toestimate the stress test section of rock,The results conform to the basic rules of groundstress division.