Study on orientation fracture blasting with shaped charge in rock

1. Introduction Stones for decoration or bowlder are excavated from ore bodies; however, the stones must be excavated with specific technique requirements. Experience shows that blasting is the method with low cost and high effi- ciency. The most familiar…     

Numerical analysis of tunnel reinforcing influences on failure process of surrounding rock under explosive stress waves

Based on mesoscopic damage mechanics, numerical code RFPA2D （dynamic edition） was developed to analyze the influence of tunnel reinforcing on failure process of surrounding rock under explosive stress waves. The results show that the propagation phenomenon of stress wave in the surrounding rock of tunnel and the failure process of surrounding rock under explosive stress waves are reproduced realistically by using numerical code RFPA2O; from the failure process of surrounding rock, the place at which surrounding rock fractures is transferred because of tunnel reinforcing, and the rockfall and collapse caused by failure of surrounding rock are restrained by tunnel reinforcing; furthermore, the absolute values of peak values of major principal stress, and the minimal principal stress and shear stress at center point of tunnel roof are reduced because of tunnel reinforcing, and the displacement at center point of runnel roof is reduced as well, consequently the stability of tunnel increases.     

岩石破碎机理的微差爆破最佳延时控制

为探究微差爆破最佳的孔间起爆延期时间,从岩石破碎机理出发,将应力波和爆生气体能量综合作用方式作为研究载体,结合波动学理论、热力学理论以及断裂力学理论,推导出应力波和爆生气体作用下的运动和动力学方程、破坏范围、作用时间和传播速度的数学公式.在此基础上,运用推导出的物理参数对哈努卡耶夫提出的延时控制半经验公式进行修正,得出了微差爆破延期时间选取的理论模型.最后,结合某露天矿进行不同段别高精度澳瑞凯雷管组合的微差爆破实验,结果显示此次试验爆破后效果最佳延期时间为25 ms,而将该地质条件的力学参数代入推导得出的最佳延期理论模型,得出延期时间为24 ms左右,说明该理论模型与本次实验结果较为吻合.     

Optimization of monitoring the stability of surrounding rock in a metal mine

Through analyzing the failure mechanics of rock under blasting effect, the optical fiber sensing system was used to monitor the strain of surrounding rock under blasting effect. Combined with practical exploration, the stability of surrounding rock was computed by numerical simulation using the blasting wave obtained from the site. According to the change regularities of displacement, stress, acceleration, and velocity of tunnels before and after explosion, the layout of key monitoring points was optimized....     

裂隙及卸荷对岩体边坡的影响

应用弹塑性力学及断裂力学的相关理论,分析讨论了裂纹的分形特性及裂隙面的压剪起裂破坏机理;分析了静载、动载和不同类型裂隙的相互作用对边坡稳定性的影响规律。结合工程实际问题,研究了边坡开挖前后其应力应变的分布规律,提出了由于开挖卸荷而引起裂纹扩展的作用机理。     

考虑爆破效应的隧道开挖损伤区及渗流场分析

针对爆破效应对围岩力学参数及渗透系数的劣化问题,根据岩石弹塑性力学、连续损伤力学、有效应力原理及渗透系数演化方程,提出了基于Hoek-Brown准则的岩体弹塑性损伤模型,并给出了模型的有限元数值求解算法.以甄峰岭隧道为工程依托,对所选断面开挖损伤区进行数值分析,通过声波检测手段确定爆破扰动范围及损伤值,修正计算力学参数和渗透系数.结果表明,考虑爆破效应后的开挖损伤区,位移值和涌水量均大于不考虑爆破效应时的数值,进行工程稳定性评价时应充分考虑爆破因素的影响.     

爆炸荷载作用下缺陷岩体破坏特征的数值模拟研究

为了研究爆炸荷载下含缺陷岩体的破坏规律,根据已有的实验结果建立了在爆炸荷载下含缺陷岩体的漏斗爆破模型,所考虑的缺陷包括孔洞、孔隙和微小的张开型节理.缺陷是随机分布的,且对于缺陷内部考虑了两种情况,一种是含水的,另一种是空的.依据已有花岗岩的实验结果,通过拟合得到了其冲击状态方程,并将其应用于炸药附近的花岗岩,而对于远离炸药的花岗岩,采用了线性状态方程.根据实验结果,将花岗岩的动态强度设计成随应变率变化的变量.模拟结果表明,在爆破荷载下,湿润的岩体比其相应干燥岩体的动态强度低;在应力波作用下缺陷密度越大,其岩体的破坏范围越小;最后,讨论了巷道附近的爆破过程对巷道稳定性的影响.     

Numerical simulation for influence of excavation and blasting vibration on stability of mined-out area

Dynamic analysis steps and general flow of fast lagrangian analysis of continua in 3 dimensions （FLAC3D） were discussed. Numerical simulation for influence of excavation and blasting vibration on stability of mined-out area was carried out with FLAC3D. The whole analytical process was divided into two steps, including the static analysis and the dynamic analysis which were used to simulate the influence of excavation process and blasting vibration respectively. The results show that the shape of right upper boundary is extremely irregular after excavation, and stress concentration occurs at many places and higher tensile stress appears. The maximum tensile stress is higher than the tensile strength of rock mass, and surrounding rock of right roof will be damaged with tension fracture. The maximum displacement of surrounding rock is 4.75 mm after excavation. However, the maxi- mum displacement increases to 5.47 mm after the blasting dynamic load is applied. And the covering area of plastic zones expands obviously, especially at the foot of right upper slope. The analytical results are in basic accordance with the observed results on the whole. Damage and disturbance on surrounding rock to some degree are caused by excavation, while blasting dynamic load increases the possibility of occurrence of dynamic instability and destruction further. So the effective supporting and vibration reducing measures should be taken during mining.     

Model experiment of rock blasting with single borehole and double free-surface

In order to improve the quality of laneways and tunnel excavation by drilling and blasting and by making effective use of explosive energy, a model experiment of rock blasting with a single borehole and a double free-surface was performed with the objective of studying the effect of parameters such as charge structure, free-surface and rock compressive strength on rock blasting. The model experiments indicate that: 1) the smaller the rock compressive strength and density, the more distinctive the cavity expanding action by blasting; 2) the powder factor in an air-decoupling charge structure is larger than that in a coupling charge structure, i.e., the explosive energy in an air-decoupling charge structure transferred to the rocks is less than that in a coupling charge structure; 3) a free-surface improves the utilizations of explosive energy; 4) an air-decoupling charge structure helps to maintain the integrity and stability of wall rock in controlled perimeter blasting, such as in roadways and tunnel excavation by drilling and blasting.     

单轴循环冲击下花岗岩力学特性与损伤演化机理

为研究循环冲击荷载下黑云母花岗岩的动态力学特性,利用改进的分离式霍普金森压杆,选取4种不同的入射波应力幅值对花岗岩试样进行等幅循环冲击,并对相关机理和试验现象进行探析.结果表明:入射波应力幅值为110.57和90.48 MPa时,随着冲击次数的增加,岩样的峰值应力逐渐降低,最大应变、平均应变率和损伤值均呈现增大趋势;入射波应力幅值为70.82 MPa时,花岗岩的峰值应力随着冲击次数的增加表现出先增强后降低的特性,而最大应变、平均应变率与损伤值则表现出相反规律;入射波应力幅值降为50.69 MPa时,岩样的力学性质基本不变,岩样未见明显的损伤.此外,研究还发现基于岩样静态压缩应力-应变曲线推求的静态裂纹起裂应力,经强度增长比例系数放大后可得到动态裂纹起裂应力,籍此能较好地解释上述循环冲击试验中所观测到的现象.     

地下厂房岩锚梁爆破参数优化设计与效果

选择具有代表性的实际光面爆破设计参数为样本，确定炸药类型、岩体裂隙发育程度、孔径、孔深、线装药密度、最小抵抗线、间距为影响岩锚梁爆破开挖效果的主要因素，利用神经网络强大的非线性映射能力，建立岩锚梁爆破参数优化模型，进行岩锚梁爆破参数优化设计。在相似地段进行保护层和岩台修面爆破试验，得出现场试验爆破参数，结果表明优化设计值与现场试验值吻合较好。对试验保护层和岩台修面爆破进行声波检测也表明其爆破质量最好，爆破松动圈范围最小。     

Dynamic Damage Model of Brittle Rock and Its Application

On the basis of shock-induced experiments and the ultrasonic tests of the damaged rocks, the damage evolution relation between the attenuation coefficient of sound wave and the damage dissipated energy is de-scribed. Based on the TCK and RDA models, a damage model which connects the shock compression and tensile damage is established. And then the damage model is implemented in LS-DYNA3D dynamic nonlinear program.Numerical simulation of deep-hole blasting of groove is studied by use of the damage model proposed. The rock damage evolution process and the distributing rules of stress field under the explosion load are described well fair-ly, which provides the theory basis for the engineering blasting design.     

Caustic study on blast-induced wing crack behaviors in dynamic–static superimposed stress field

This paper studies blast-induced wing crack behavior in a dynamic–static superimposed stress field using high-speed photography in combination with the optical method of caustics. With a static–dynamic loading setup, four PMMA plate specimens with pre-existing cracks under different static loading and the same dynamic loading were tested to observe the mechanical characteristics and the kinematic characteristics of blast-induced wing cracks during the propagation process, including crack length, crack velocity and dynamic stress intensity factor (SIF) at the crack tip. The results show that the behavior of the blast-induced wing crack is affected by the explosion stress wave and initial static stress, and the initial static stress with the direction being perpendicular to the wing crack propagation direction hinders crack propagation. Furthermore, the boundary constraint condition of the specimen plays an important role on the behavior of the crack propagation in the experiment.     

不同围岩级别和锚固介质下锚杆动测波形特征分析

基于应力波反射法,通过不同围岩级别和锚固介质中锚杆的瞬态动力响应实验研究,对锚杆的加速度响应曲线的波形特征进行分析.结果表明,随着龄期的增长,固端反射信号非常强烈,而底端反射信号越来越微弱,甚至很难识别;围岩和锚杆介质均匀密实的锚杆其信号相对平缓一些.     

Vibration Effect and Damage Evolution Characteristics of Tunnel Surrounding Rock Under Cyclic Blasting Loading

Model test studies based on the similarity theory were conducted to investigate vibration effect and damage evolution characteristics of tunnel surrounding rock under push-type cyclic blasting excavation. The model was constructed with a ratio of 1:15. By simulating the tunnel excavation of push-type cyclic blasting, the influence of the blasting parameter change on vibration effect was explored. The damage degree of tunnel surrounding rock was evaluated by the change of the acoustic wave velocity at the same measuring point after blasting. The relationship between the damage evolution of surrounding rock and blasting times was established. The research results show that:① In the same geological environment, the number of delay initiation is larger, the main vibration frequency of blasting seismic wave is higher, and the attenuation of high frequency signal in the rock and soil is faster. The influence of number of delay initiation on blasting vibration effect cannot be ignored; ② Under push-type cyclic blasting excavation, there were great differences in the decreasing rates of acoustic wave velocity of the measuring points which have the same distance to the blasting region at the same depth, and the blasting damage ranges of surrounding rock were typically anisotropic at both depth and breadth; ③ When blasting parameters were basically kept as the same, the growth trend of the cumulative acoustic wave velocity decreasing rate at the measuring point was nonlinear under different cycle blasting excavations; ④ There were nonlinear evolution characteristics between the blasting cumulative damage (D) of surrounding rock and blasting times (n) under push-type cyclic blasting loading, and different measuring points had corresponding blasting cumulative damage propagation models, respectively. The closer the measuring point was away from the explosion source, the faster the cumulative damage extension. Blasting cumulative damage effect of surrounding rock had typically nonlinear evolution properties and anisotropic characteristics.     

Simulation of the relationship between roadway dynamic destruction and hypocenter parameters

Many factors can induce rock burst. Shock energy and shock distance are two key factors affecting rock burst. The 32101 roadway of the Xingcun coal mine, which has a tendency for rock burst, was used as an example. The dynamic module of Itasca's FLAC (Fast Lagrangian Analysis of Continua) 2D explicit finite-difference software was used to simulate the roadway's destruction. The vibration velocity and displacements of the rock surrounding the roadway were modeled for different shock energies and hypo-center distances. The simulation results indicate that the vibration velocity and displacement of rock surrounding the roadway have a quadratic relationship to the shock energy and a power law relationship to the distance of the hypocenter from the roadway. A dynamic view of the process was obtained from a series of "snap-shots" collected at 100 different time steps. This shows an isolat-ing "river" is first formed at the hypocenter. The region above the "river" is a low stress zone while below the "river" a high stress zone exists. This high stress zone surrounds the ribs of the roadway in a "double ear" pattern. Continuous and repeated action of the high stress in the "double ear" shaped zone destroys the roadway.     

超高应变率下岩石的破坏机理

通过对大理石的轻气炮试验进行三维数值仿真重现,探索了岩石在超高应变率下的破坏机理.大理石试样中两个高速应力计的实测应力信号被用作数值模拟的匹配目标,结果表明,在高速冲击压缩载荷下,细观静水压破坏是大理石的主要破坏机制,而不是通常认为的细观剪切或拉伸破坏.此外,为再现不同冲击速度下大理石的物理实验观测数据,提出了新的考虑...     

岩体爆裂成缝的计算机模拟分析

分析了岩体爆裂成缝的计算机模拟的可行性和影响因素，编制了计算机模拟程序，计算机模拟表明，爆裂成缝是爆炸应力波和爆生气体联合作用的结果。     

Numerical simulation study on hard-thick roof inducing rock burst in coal mine

In order to reveal the dynamic process of hard-thick roof inducing rock burst, one of the most common and strongest dynamic disasters in coal mine, the numerical simulation is conducted to study the dynamic loading effect of roof vibration on roadway surrounding rocks as well as the impact on stability. The results show that, on one hand, hard-thick roof will result in high stress concentration on mining surrounding rocks; on the other hand, the breaking of hard-thick roof will lead to mining seismicity, causing dynamic loading effect on coal and rock mass. High stress concentration and dynamic loading combination reaches to the mechanical conditions for the occurrence of rock burst, which will induce rock burst. The mining induced seismic events occurring in the roof breaking act on the mining surrounding rocks in the form of stress wave. The stress wave then has a reflection on the free surface of roadway and the tensile stress will be generated around the free surface. Horizontal vibration of roadway surrounding particles will cause instant changes of horizontal stress of roadway surrounding rocks; the horizontal displacement is directly related to the horizontal stress but is not significantly correlated with the vertical stress; the increase of horizontal stress of roadway near surface surrounding rocks and the release of elastic deformation energy of deep surrounding coal and rock mass are immanent causes that lead to the impact instability of roadway surrounding rocks. The most significant measures for rock burst prevention are controlling of horizontal stress and vibration strength.     

基于应变率相关动力特性的岩体爆破破坏区范围研究

岩体动态强度特性及受力变化规律是研究炮孔近区岩体破坏特征的关键,采用合理的动态强度模型直接决定了炮孔破坏区范围计算结果的正确性.因此,利用理论分析与现场试验相结合的方法,研究了基于应变率相关动力强度特性下炮孔破坏区范围的计算方法.利用柱面波的位移协调方程,推导了炮孔近区岩体质点的应变率计算公式,并应用于岩体应变率相关的...