Analysis Of The Influence Of Raise Boring Reaming Drilling Well Stability In The Softened Mudstone Formation

In this paper,through a combination of theoretical analysis and laboratory experiments,combined with the engineering geological conditions of the Jinglong Pumped Storage Power Station,the classification of the surrounding rock of the wellbore construction rig is carried out first,and then the mudstone softened by the water in the surrounding rock of the wellbore is submerged.Softening test to obtain the softening law of its mechanical parameters.Finally,an analytical model of the displacement and immersion time of the surrounding rock of the shaft considering engineering parameters,rock mechanical parameters,softening effects,and boundary conditions was established to evaluate the reaming construction process of the reverse well drilling method.The safety of the shrinkage of the middle shaft and the instability of the surrounding rock provide a reference for the engineering application of the reverse well drilling method.Based on the fact that the surrounding rock classification methods for the reverse well drilling method at home and abroad are not clear,by comparing and analyzing the rock breaking mechanism of the reverse well drilling rig and the rock breaking mechanism of the TBM tunneling machine in tunnel engineering,this paper draws on the surrounding wall of the TBM construction tunnel.The experience and advantages of rock classification,the compressive strength,abrasion resistance,and rock integrity of the rock are the three main factors that affect the construction of backhole drilling rigs.Due to the determination of the surrounding rock stability of the reverse rig construction,the influence of water absorption softening of the surrounding rock on the stability of the shaft is not considered,and the water absorption softening of the surrounding rock will cause the shrinkage of the shaft and the instability of the surrounding rock.In this thesis,through the conventional mechanical test research of mudstone,the physical properties such as the natural moisture content,density,uniaxial compressive strength,and shear strength of the mudstone are obtained in this test.The relationship between water absorption,uniaxial compressive strength,elastic modulus,Poisson's ratio and immersion time,and the effect of different water pressure and water temperature on the softening effect of mudstones.Finally,based on the damage variables and brittleness coefficients,the mudstones were established.Soften the depth model.Through the calculation of the counter-bore reaming drilling,the displacement problem on the hollow surface of the reaming well is reduced to a circular axisymmetric problem,and the displacement formula of the surrounding rock of the well is obtained according to the plastic zone displacement solution of the elastoplastic model.The results of the softening test were used to derive the displacement formula of the surrounding rock of the reamed shaft with no support in consideration of the softening effect of the mudstone.Finally,an analytical model of the displacement of the surrounding rock of the shaft and the immersion time considering the boundary effect was established.Based on the actual engineering geology of the Longlong Pumped Storage Power Station,this model provides a reference for the actual application of the reverse well drilling method;through self-consistent analysis,the law of change in the displacement of the surrounding rock of the shaft and various parameters and The actual situation is consistent,which further verifies the self-conformity of the analytical model of the displacement of the surrounding rock of the shaft and the immersion time established in this paper.