| The water energy resources of our country are mainly concentrated in the southwest area,which is mostly high mountain topography.Large-scale rock high slope excavation is needed for the construction of hydropower projects in this area.Drilling blasting is the main means of rock slope excavation in hydropower engineering at present.The stress wave produced by blasting and the relaxation of excavation and unloading will inevitably cause damage to the retaining rock mass of the slope,resulting in the deterioration of the integrity of the slope rock mass and the decrease of mechanical properties.Therefore,it is necessary to study the influence of blasting excavation damage zone on the stability of rock slope,and provide necessary theoretical support for the stability evaluation and support design of slope blasting excavation during construction period.In this paper,the weakening law of rock mass mechanical parameters in rock slope blasting excavation area is studied by combining theoretical analysis,numerical simulation and field test.The influence of the weakening of rock mass mechanical parameters on the static and dynamic stability of slope is analyzed.The main research contents and conclusions are as follows:(1)This paper presents a method for estimating rock mass mechanical parameters based on Hoek-Brown strength criterion and acoustic wave detection,and quantitatively determines the variation of Hoek-Brown criterion disturbance factor D in the damage area based on acoustic wave detection data of left bank dam shoulder groove slope of Baihetan Hydropower Station.According to the results,the degree of rock mass damage at different depths in slope damage area is different,and the disturbance factor D is not a constant,but decreases linearly with depth.(2)On the basis of the method of estimating the mechanical parameters of Hoek-Brown strength criterion rock mass and the variation law of disturbance factor D in the blasting excavation damage area,the weakening law of rock mass deformation parameters and strength parameters in the blasting excavation damage area of left bank dam shoulder groove slope of Baihetan Hydropower Station is studied.The results show that with the increase of rock mass depth in the damage area,the deformation modulus of rock mass increases linearly,while the uniaxial tensile strength,uniaxial compressive strength,cohesion and internal friction angle increase nonlinearly,and the uniaxial compressive strength of rock mass is the most affected by blasting damage and the internal friction angle is the least affected.(3)Based on the Slide numerical calculation software,the influence of the weakening of rock mass mechanical parameters on the static stability of the slope is studied by using the limit equilibrium method.The results show that the disturbance factor D changed linearly compared with the constant D=1,the static safety factor increased by 20%～25.71%for the GSI sequence,the static safety factor increased by32%～68%for the m_i sequence,the higher the slope height,the greater the slope angle.the greater the thickness of the damage zone,the greater the influence of the weakening of rock mass mechanical parameters on the static stability of the slope,and the degree of influence of each factor from large to small is slope angle,slope height and thickness of the damage zone.(4)By using the Sarma method and the quasi-static formula,the influence of the weakening of rock mass mechanical parameters on the dynamic stability of the slope is studied.The results show that the disturbance factor D changed linearly compared with the constant D=1,the dynamic safety factor increased by 20%～25.71%for the GSI sequence,the dynamic safety factor increased by 24%～40%for the m_isequence,the same law and influence degree as the static stability analysis.According to the dynamic disturbance of blasting excavation,the safety coefficient of slope is8.09～13.82%lower than that of static condition. |
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