【作者】 叶志伟；

【导师】 陈明；

【作者基本信息】 武汉大学 ， 水工结构工程， 2022， 博士

【摘要】 钻孔爆破作为岩体开挖的手段,因具有高效经济的优势,被广泛应用于水利水电、铁道工程、交通工程等基础工程建设领域以及矿产资源开采中。随着我国“双碳”战略目标的提出,推动经济社会绿色转型和系统性深刻变革是大势所趋。实现爆炸能量的高效利用是响应国家“碳达峰、碳中和”重大战略目标,实现经济可持续发展的必然要求。研究爆破孔内流固耦合作用机制与效应,对加深爆破流固耦合作用过程的认识、简便准确地计算爆炸荷载、掌握堵塞结构运动规律、揭示钻孔爆破破岩机理、优化爆破设计及提高炸药能量利用率等方面具有重要的理论意义和工程实用价值。本文以“爆破孔内流固耦合作用机制与效应研究”为题,采用理论分析、数值模拟、室内试验与现场试验相结合的综合研究方法,开展了一系列的研究工作,主要的研究内容及研究成果如下:(1)基于爆炸力学理论,分析了空气耦合爆破孔内流体介质与炮孔壁的相互作用,揭示了炸药、孔壁介质及不耦合系数对空气耦合爆破孔壁压力峰值的影响机理。建立了空气耦合单孔爆破有限元模型,基于一阶段等熵膨胀理论与两阶段等熵绝热膨胀理论,结合数值模拟计算结果,分别提出了空气介质小不耦合系数爆破孔壁压力峰值计算方法与空气耦合轮廓爆破孔壁压力峰值计算方法,提升了空气耦合爆破孔壁压力峰值的计算精度。(2)基于爆炸力学理论,分析了水耦合爆破孔内流体介质与炮孔壁的相互作用,揭示了水耦合爆破孔壁压力峰值随孔壁介质波阻抗及不耦合系数的变化规律。基于理论分析结果,并结合量纲和谐准则,建立了水耦合爆破孔壁压力峰值的简化计算模型。采用流固耦合动力有限元方法,模拟得到不同工况下水耦合爆破孔壁压力峰值,结合数值模拟结果及简化计算模型,提出了水介质小不耦合系数爆破孔壁压力峰值计算方法与水耦合轮廓爆破孔壁压力峰值计算方法,试验数据验证了计算方法的可靠性,初步解决了水耦合爆破孔壁压力峰值的计算问题。(3)基于轴向一维运动模型,分析了爆破孔内流体介质与堵塞结构的相互作用,考虑了堵塞结构在冲击波作用下压缩后回弹对滑动摩擦阻力的影响,提出了附加滑动摩擦阻力的计算方法,建立了堵塞结构运动过程的“分时分段”解算模型,揭示了滑动摩擦阻力沿炮孔轴向的分布规律。提出了允许堵塞结构部分冲出炮孔的“运移式”优化原则。针对钻孔岩屑堵塞材料,计算了不同工况下炮孔最优堵塞长度,揭示了炮孔最优堵塞长度随爆生气体压力峰值与炮孔直径的变化规律,提出了炮孔最优堵塞长度计算方法。通过现场应用证实了该计算方法有利于充分发挥爆生气体的破岩作用。(4)采用流固耦合数值模拟方法,分析了爆破孔内流固耦合作用下岩体的爆破破坏效应,得到了炮孔周围岩体的爆破损伤分布及变化特征,考虑爆轰波的轴向传播过程及冲击波在岩体内的传播过程,以岩体爆破破坏体积为评价指标,提出了一种定量化区分冲击波与爆生气体破岩作用的方法,分析了岩体特性及临空面条件对冲击波与爆生气体破岩作用贡献占比的影响,揭示了台阶爆破中岩体发生爆破破坏的主要原因是爆生气体作用。结合现场试验结果,验证了该结论的可靠性,为寻求有效工程措施以充分发挥爆生气体的破岩作用提供了理论依据。(5)采用室内试验的方法,研究了空气耦合爆破孔壁压力峰值。采用无缝薄壁钢管模拟炮孔,以应变片为传感器,测试得到钢管外壁环向应变,基于动荷载作用下薄壁圆筒的动力学方程,推导了薄壁圆筒外壁环向应变与内壁径向应力的关系式,提出了孔壁压力峰值的测试方法,测试得到了多种工况下的孔壁压力峰值,验证了前述空气耦合爆破孔壁压力峰值计算方法,为孔壁压力峰值的测试与计算提供了参考。更多还原

【Abstract】 As a means of rock mass excavation,drilling and blasting has been widely used in water conservancy and hydropower project,railway engineering,transportation engineering and other infrastructure construction fields as well as mineral resources exploitation because of its high efficiency and economy.As the strategic goal of emission peak and carbon neutrality is raised,it is the general trend to promote greener economic besides systematic and profound changes.Realizing the efficient utilization of explosion energy is the inevitable requirement of responding to the major strategic goal of emission peak and carbon neutrality and realizing sustainable economic development.It is of great theoretical significance and engineering practical value to study the mechanism and effects of fluid-structure interaction in borehole for deepening the understanding of the process of fluid-structure interaction in blasting,calculating the explosion load simply and accurately,mastering the motion law of stemming structure,revealing the rock breaking mechanism in drilling and blasting,optimizing blasting design,and improving explosive energy utilization.With the title of "Study on the mechanism and effects of fluid-structure interaction in borehole",a series of research work has been carried out in this paper by using a comprehensive research method combining theoretical analysis,numerical simulation,laboratory tests and field tests.The main contents and results are shown as follows:(1)Based on the theory of explosion mechanics,the interaction between fluid medium in borehole and borehole wall in air-coupled blasting is analyzed,and the influence mechanism of explosive,borehole wall medium and decoupling coefficient on the peak pressure on borehole wall in air-coupled blasting is revealed.The single-hole finite element model of in air-coupled blasting is established.Based on the one-stage isentropic expansion theory and two-stage isentropic adiabatic expansion theory,combined with the numerical simulation results,the calculation methods of the peak pressure on borehole wall with small decoupling coefficient in air-coupled blasting and the peak pressure in air-coupled contour blasting are proposed,respectively.The new methods can improve the calculation accuracy of the peak pressure on borehole wall in air-coupled blasting.(2)Based on the theory of explosion mechanics,the interaction between fluid medium in borehole and borehole wall in water-coupled blasting is analyzed,and the influence mechanism of explosive,borehole wall medium and decoupling coefficient on the peak pressure on borehole wall in water-coupled blasting is revealed.Based on the theoretical analysis results and the principle of dimensional harmony,a simplified calculation model of the peak pressure on borehole wall in water-coupled blasting is established.Using the fluidstructure coupling dynamic finite element method,the peak pressure on borehole wall in water-coupled blasting under different conditions is simulated.Combined with the numerical simulation results and the simplified calculation model,the calculation method of the peak pressure in water-coupled blasting with small decoupling coefficient and the peak pressure in water-coupled contour blasting are proposed,which has been verified by the existing experiment results.The calculation problem of the peak pressure on borehole wall in watercoupled blasting is solved primarily by this way.(3)Based on the axial one-dimensional movement model,the interaction between fluid medium in borehole and stemming structure is analyzed.Considering the influence of the rebound of the stemming structure after compression under the action the shock wave on the sliding friction resistance,a calculation method of additional sliding friction resistance is proposed.A time-sharing piecewise solution model of the movement process of the stemming structure is established,and the distribution law of sliding friction resistance along the axial direction is revealed.An optimization principle that allows the part of stemming structure to rush out of borehole is proposed.Aiming at the common stemming materials of rock debris in engineering blasting,the optimal stemming length under different conditions is calculated,and the variation law of the optimal stemming length with the peak gas pressure and borehole diameter is revealed.In view of the above,a new method for calculating the optimal stemming length is proposed and the field application proves that the calculation method is beneficial to give full play to the rock-breaking effect of the gas pressure.(4)Based on the fluid-structure coupling numerical simulation method,the blasting failure effect of rock mass under the fluid-structure coupling action in borehole is analyzed,and the blasting damage distribution and variation characteristics of rock mass around the borehole are obtained.Considering the axial propagation process of detonation waves and the propagation process of shock waves in rock mass,a quantitative method to distinguish the rock breaking effect of the shock wave and gas pressure is proposed by taking the blasting failure volume of rock mass as the evaluation index.The influence of rock mass characteristics and free surface conditions on the contribution ratio of the shock wave and gas pressure to rock mass failure volume is analyzed,and it is revealed that blasting gas is the main reason for the blasting failure of rock mass in bench blasting.Combined with the field experiment results,the reliability of the conclusion is verified,which provides a theoretical basis for seeking effective engineering measures to give full play to the rock breaking effect of the gas pressure.(5)Laboratory experiments are adopted to study the peak pressure on borehole wall in air-coupled blasting.Thin-walled cylinder seamless steel pipe is used to simulate borehole,take strain gauge as sensor,the circumferential strain of outer wall of steel pipe is obtained.Based on the dynamic equation of thin-walled cylinder under dynamic load,the relationship between the circumferential strain of outer wall and radial stress of inner wall of thin-walled cylinder is deduced.Based on this,the test method of the peak pressure on borehole wall is proposed,and the peak pressure under various conditions is obtained,which can verify the calculation method in air-coupled blasting proposed above.The research provides a reference for the measurement and calculation of the peak pressure on borehole wall.更多还原