Failure mechanism and control technology of water-immersed roadway in high-stress and soft rock in a deep mine

Aiming at soft rock ground support issues under conditions of high stress and long-term water immersion, the ground failure mechanism is revealed by taking the deep-water sumps of Jiulong Mine as the engineering background and employing field investigation, tests of rock structure, mechanical properties and mineral composition. The main factors leading to the surrounding rock failure include the high and complex stress state of the water sumps, high-clay content and water-weakened rock, and the unreasonable support design. In this paper, the broken and fractured rock mass near roadway opening is considered as ground small-structure, and deep stable rock mass as ground large-structure. A support technology focusing on cutting off the water, strengthening the small structure of the rock and transferring the large structure of the rock is proposed. The proposed support technology of interconnecting the large and small structures, based on high-strength bolts, high-stiffness shotcrete layer plugging water,strengthening the small structure with deep-hole grouting and shallow-hole grouting, highpretensioned cables tensioned twice to make the large and small structures bearing the pressure evenly,channel-steel and high-pretensioned cables are used to control floor heave. The numerical simulation and field test show that this support system can control the rock deformation of the water sumps and provide technical support to similar roadway support designs.     

Parametric study on the axial performance of a fully grouted cable bolt with a new pull-out test

Modified cable bolts are commonly used in underground mines due to their superior performance in preventing bed separation when compared with plain strands. To better test the axial performance of a wide range of cable bolts,a new laboratory short encapsulation pull test(LSEPT) facility was developed. The facility simulates the interaction between cable bolts and surrounding rock mass,using artificial rock cylinders with a diameter of 300 mm in which the cable bolt is grouted. Furthermore,the joint where the load is applied is left unconstrained to allow shear slippage at the cable/grout or grout/rock interface.Based on this apparatus,a series of pull tests were undertaken using the MW9 modified bulb cable bolt.Various parameters including embedment length,test material strength and borehole size were evaluated. It was found that within a limited range of 360 mm,there is a linear relationship between the maximum bearing capacity of the cable bolt and embedment length. Beyond 360 mm,the peak capacity continues to rise but with a much lower slope. When the MW9 cable bolt was grouted in a weak test material,failure always took place along the grout/rock interface. Interestingly,increasing the borehole diameter from 42 to 52 m in weak test material altered the failure mode from grout/rock interface to cable/grout interface and improved the performance in terms of both peak and residual capacity.     

锚杆周围的地下电流密度分布及其在地面上产生的磁场

锚杆广泛应用于地质工程中,例如斜坡控制。工程中经常会出现空锚、断锚等锚固质量问题,所以必须对锚杆进行无损检测。近些年来,锚杆的锚固质量检测技术得到了快速发展。电磁法检测已得到广泛关注,其理论基础必须深入研究。本文就地下锚杆建立了物理模型,通过计算得到了锚杆周围的地下电流密度分布解析式,并计算出了地下电流在地面上产生的磁场,得出了地面上磁场仅由锚杆电流决定的结论。这一结果可以作为对电磁法检测锚杆进行深入研究的理论基础。     

The dynamical loading on rock with different loading wave shapes conventional SHPB

Since loading wave shapes are very important in the study of rock dynamical properties, a new procedure for obtaining a variety of wave shapes using equi-diameter impact hammer of conventional SHPB device is proposed based on theoretical analysis. Experiment shows that different loading wave shapes can be obtained through varying the radius at impact end of hammer. Experiment results are quite consistent with the theoretical analysis. Project supported by the National Natural Science Fundation of China Synopsis of the author Xu Jichen, senior engineer, born in January 1951. Major research fields: Rock fracture mechanics and modern experimental method and technique in rock impact dynamics.     

冲击载荷下脆性岩板损伤断裂演化的实验模拟研究

在矿山运输系统中,井壁围岩冲击损伤破坏对经济和安全效益的影响是至关重要的,因为动态冲击载荷对井壁围岩和支护结构会产生严重的削弱破坏作用,室内研究表明,岩石样品如岩板在动态载荷的冲击作用下会失效。为研究在低速冲击载荷作用下,脆性岩石损伤断裂的演化过程,利用分离式霍普金森压杆(SHPB)装置中压缩气体发射球体子弹对脆性岩板进行变角度冲击损伤实验,岩板受到冲击后,边缘出现凹坑,表面裂纹从撞击凹坑直达岩板边缘,实验中样品的表面裂纹能有效代表试样内部的开裂状况,能有效反映冲击能量的耗散、破裂区面积与裂纹表面积随入射能量呈非线性增长趋势,同时与入射角度相关,但当破裂区面积急剧下降时,裂纹表面积反而急剧上升,表明裂纹的发生发展有明显的孕育期,在入射能量达到临界值前,主要表现为裂纹孕育增长,在达到临界值后,发生宏观断裂破坏,裂纹面积呈负增长,破裂区面积增大。实验结果分析表明在实际工程中,围岩和支护结构的抗冲击的最优化设计角度范围在15°～30°。     

高流变围岩泵房注浆加固的试验研究

根据相似理论,对万年矿-440泵房高流变围岩注浆加固前后变形特性进行相似材料模拟研究,得出了其变形规律:高流变围岩变形可以分为扩帮整修加速阶段、相对稳定阶段和动压阶段等三个阶段;注浆加固使泵房围岩岩体变形由结构高流变特性转为线弹性或是弹塑性。试验结果表明,采用注浆加固高流变围岩的方法是可行的,对工程实践是有一定指导意义的。     

A novel rock bolting system exploiting steel particles

The effectiveness of rock bolting in ground control has been extensively investigated, mainly for resin based systems. Alternative coupling materials are needed to have good mechanical performance and to reduce the economic impact. This study proposed a new bolting system exploiting steel particles as coupling material. The applicability of this system was assessed by laboratory and field pullout tests, assisted by digital imaging correlation (DIC), infrared thermography (IRT) and acoustic emission (AE). The results indicated that, for a 20 mm diameter bolt, the suitable steel particle size and corresponding inner diameter of borehole were 1.4 and 28 mm, respectively. For bolts installed in steel tubes, the particles improved the loading capacity compared to the resin bonded ones. Additional pullout tests on cement blocks indicated that steel particles can be effective for hard rock, whilst resin was a better choice for bolting of soft rock. Similar understanding was obtained by pullout tests in engineering fields, which demonstrated that the steel particles coupled bolts can provide favorable effects in hard rock mass, while the effects were negligible when installed in extremely soft coal mass. The wide set of multi-technique measurements helped to understand the mechanisms involved in the performance of the bolting system with coupling steel particles.     

锚杆-围岩结构的耦合振动和减振

锚杆支护是隧道施工中常见的支护手段,而随着施工工况日趋复杂,锚杆与围岩的组合结构也承受着各类动力荷载的影响。针对隧道中单根锚杆的受力特性有较多研究,而对于锚杆和围岩组合体的动力特性研究较少。对锚杆-围岩结构进行整体分析,简化出一种巷道顶板锚杆支护模型,结合动力学双梁理论,建立并求解出模型动力学方程;运用MATLAB软件进行数值模拟,研究不同支护参数下结构的自振特性以及在外荷载作用下的动力响应,提出减振措施;利用有限元软件GTS NX建立二维模型,验证支护体系的安全性。结果表明：锚杆-围岩结构的动力特性与锚固段长度、锚杆间距和锚杆直径有关。在所建模型中,随着锚固段长度与锚杆间距的适当增加,结构动力响应明显减弱;随着锚杆直径的变化,结构动力特性的变化情况较复杂,结构不同部位的动力响应变化趋势差别较大。     

高能级强夯处理抛填路基的有效加固深度

高能级强夯的加固效果显著,应用范围越来越广泛,有效加固深度是评判加固效果和确定强夯方案的重要指标.以10000 kN·m高能级强夯加固某抛填路基工程为背景,采用FLAC 3D有限差分软件进行单点多次夯击的强夯数值模拟,以夯击后的应力为标准来计算有效加固深度.结果表明:随夯击次数的增加,有效加固深度先增大后稳定,6击后有...     

Effect of dynamic loading conditions on the dynamic performance of MP1 energy-absorbing rockbolts: Insight from laboratory drop test

Energy-absorbing rockbolts have been widely adopted in burst-prone excavation support, and their serviceability is closely related to the frequency and magnitude of seismic events. In this research, the splittube drop test with varying impact energy was conducted to reproduce the dynamic performance of MP1rockbolts under a wide range of seismic event magnitudes. The test results showed that the impact process could be subdivided into four distinct stages, i.e. mobilization, strain hardening, pla...     

Rheological properties of surrounding rock in deep hard rock tunnels and its reasonable support form

Second lining stability, which is the last protection in tunnel engineering, is critically important. The rheological properties of the surrounding rock heavily affect second lining stability. In this work, we used laboratory triaxial compressive rheological limestone tests to study nonlinear creep damage characteristics of surrounding rock mass in construction projects. We established a nonlinear creep damage constitutive model for the rock mass, as well as a constitutive model numerical implementation made by programming. Second, we introduced a new foam concrete with higher compression performance and good ductility and studied its mechanical properties through uniaxial and triaxial tests. This concrete was used as the filling material for the reserved deformation layer between the primary support and second lining. Finally, we proposed a high efficiency and accuracy staged optimization method. The minimum reserved deformation layer thickness was established as the optimization goal, and the presence of plastic strain in the second lining after 100 years of surrounding rock creep was used as an evaluation index. Reserved deformation layer thickness optimization analysis reveals no plastic strain in the second lining when the reserved deformation minimum thickness layer is 28.50 cm. The results show that the new foam concrete used as a reserved deformation layer filling material can absorb creep deformation of surrounding rock mass, reduce second lining deformation that leads to plastic strain, and ensure long-term second lining stability.     

二道垭隧道开挖与支护的数值模拟分析

大量工程实践表明,岩体工程开挖后的应力调整和变形并不是瞬时完成,本文采用大型有限元工程模拟分析软件ABAQUS,模拟二道垭隧道的开挖与支护过程,研究隧道开挖后考虑不同的应力释放比例后再支护时,围岩的变形及锚杆的受力情况. 计算结果表明：对于松软岩层来说,考虑应力释放后再支护的计算结果更好地反映工程围岩的变形和破坏特性.     

二道垭隧道开挖与支护的数值模拟分析

大量工程实践表明，岩体工程开挖后的应力调整和变形并不是瞬时完成，本文采用大型有限元工程模拟分析软件ABAQUS，模拟二道垭隧道的开挖与支护过程，研究隧道开挖后考虑不同的应力释放比例后再支护时，围岩的变形及锚杆的受力情况．计算结果表明：对于松软岩层来说，考虑应力释放后再支护的计算结果更好地反映工程围岩的变形和破坏特性．     

锚杆锚固质量无损检测数据的处理方法研究

以声波法为基础的无损检测技术已经逐渐取代传统的拉拔实验成为锚杆锚固质量检测的主要手段。随着锚杆锚固技术在各类土木工程中的应用日益增加,锚杆锚固质量无损检测数据处理方法的研究工作也越来越受到重视。本文在分析锚杆锚固质量无损检测原理的基础上提出了以Hilbert变换为基础的数据处理方法,并将该方法应用于实际工程中,验证了其可行性。     

A new cable truss support system for coal roadways affected by dynamic pressure

The support of coal roadways is seriously affected by intense dynamic pressures. This can lead to problems with large deformation of the roof and the two side walls of coal roadways. Rapid convergence of the walls and roof, a high damage rate to the bolts and cables, or even abrupt roof collapse or rib spalling can occur during the service period of these coal roadways. Analyzing the main support measures used in China leads to a proposed new cable truss supporting system. Thorough study of the entire structure shows the superiority of this design for roadways suffering under dynamic pressure. A corresponding mechanical model of the rock surrounding the cable truss system is described in this paper and formulas for calculating pre-tightening forces of the truss cable, and the minimum anchoring forces, were deduced. The new support system was applied to a typical roadway affected by intensive dynamic pressure that is located in the Xinyuan Coal Mine. The results show that the largest subsidence of the roof was 97 mm, the convergence of the two sides was less than 248 mm, and the average depth of the loose, fractured layer was only 6.12 mm. This proves that the new support system is feasible and effective.     

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.     

聚氨酯夹芯整体层连复合材料的力学性能研究

整体中空层连复合材料是一种新型的具有特殊结构的夹芯复合材料,主要由经纱与纬纱编织组成的表层和连接2个表层的具有特殊结构的芯部整体编织而成.本文简述了整体中空层连复合材料的复合成型工艺及填充聚氨酯发泡剂的过程,并以高度为25mm填充有聚氨酯发泡剂的玻璃纤维整体中空层连复合材料为例,采用INSTRON电子万能试验机对其进行平压实验;经向和纬向的侧压实验以及弯曲实验等,以测量该种材料的静态力学性能,获得该材料的力学性能参数.同时,文章还采用37mm的SHPB装置,对该种材料的动态力学性能进行了测试研究,得到了材料在动态载荷下的应力应变曲线,分析了该种材料的动态吸能特性以及破坏模式,并对比分析了整体中空层连复合材料经向和纬向的性能差异,得到一些有益结论.为此新型材料在工程结构中的应用提供了一定的参考.     

岩石材料动态断裂韧性的实验研究

为了研究岩石类材料的动态力学性能及动态破坏机理,防止出现岩石爆裂造成灾难性破坏,根据中心裂纹圆盘试件断裂韧性测试方法和分离式霍普金森压杆的基本原理,在SHPB装置上测试了花岗岩的动态断裂韧性。对测试结果按照SHPB基本原理进行处理,以试件两端平均载荷带入准静态公式得到动态断裂韧性。处理结果表明,用试件两端平均载荷获得岩石动态断裂韧性的实验方法有效的;花岗岩的动态断裂韧性具有加载速率相关性,随着加载速率的增加断裂韧性增大。     

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.     

脆性材料SHPB试验中实现近似恒应变率加载必要性的研究

基于分离式霍普金森压杆（SHPB）试验的数值模拟,对脆性材料SHPB试验中是否需要实现近似恒应变率加载的必要性进行了研究。结果表明在脆性材料的SHPB试验中,即使整形入射应力波在反射应力波中产生了一个近似平台,脆性材料试样中仍旧存在显著的由惯性产生的径向围压,说明在SHPB试验中实现了由反射应力波中的近似平台所表征的近似恒应变率加载也不能表示SHPB试样中的应变率为近似恒定。因此,在脆性材料SHPB试验中应用波形整形技术并不能改变转折应变率表征SHPB试样中应力状态转变的特性。无论是否采用了波形整形技术,应用脆性材料SHPB试验结果时都应考虑惯性引起的径向围压的影响。