Coal-rock structures in deep coal-bearing strata, due to their intricate mechanical properties, are the primary carriers of rock burst hazards. This study, incorporating singular point catastrophe theory, develops a mathematical model of the coal-rock to investigate the instability mechanisms and influencing factors of these structures. The results reveal the following: (1) By integrating the sharp corner mutation model, the mathematical formulation of the failure criterion for the coal-rock composite system was derived. (2) The failure process of the coal-rock composite structure is gradual. The strength of the coal significantly influences the peak instability strength of the composite structure, whereas the strength of the rock has a relatively minor impact on it. (3) As the proportion of rock thickness decreases, the number of fractures within the rock also diminishes, with these fractures primarily developing on the side of the rock adjacent to the coal-rock contact surface. The findings of this research can serve as valuable references for the prevention of rockbursts in the protection of coal pillars.

In order to explore the mechanism of rockburst in coal seam with rock parting, a combination of on-site and numerical experiment is used to study the failure and instability process, crack propagation mechanism, and influencing factors. The following four points were addressed: (1) the instability is a process that roadway in coal seam with rock parting go through from stable locking in the initial stress unloading stage to slipping unlocking, and then to spatter ejection in slipping dynamic load disturbance stage. (2) The fracture development caused by unloading excavation of coal seam with rock parting will change from shear crack to tensile crack. In this process, coal-rock contact surface slip and coal-rock fracture are coupled with each other. (3) The greater the mining depth is, the greater the lateral pressure coefficient is, and the higher the rockburst risk is. On the contrary, the lower the risk of rockburst. (4) When choosing the support form of roadway in coal seam with rock parting, the two supporting forms of bolting (cable) and supplementary masonry support should be preferred. The results enrich the theory of the dynamics of surrounding rock fracture in coal mine, further clarify the potential dangers to mining-area roadways and working faces, and provide technical information to ensure the safe and efficient mining of bifurcated coal seam.

Unloading excavation can increase the possibility of rock burst, especially for coal seam with rock parting. In order to explore the evolution process of rock burst under lateral unloading, the combination of in situ measures and numerical experiments is used to study. The following four points were addressed: (1) the coal seam with rock parting easily causes the stick-slip and instability along the interface, and the process of stick-slip and instability has hysteresis characteristics; (2) the greater the degree of unloading or the smaller the interface friction angle of the Coal-Rock Parting-Coal Structure (CRCS), the more likely it is for stick-slip and instability to occur; (3) the abnormal increase of shear stress and slip dissipation energy can be used as the precursory information of the stick-slip and instability of CRCS; (4) the damage intensity of rock burst induced by stick-slip and instability of CRCS can be reduced by reducing the unloading speed or increasing the roughness of interface. The research results can be used for early warning and controlling of dynamic disaster induced by stick-slip instability in coal seam with rock parking.

Rockburst with structural instability is prone to occur during mining and excavation in the bifurcation area of coal seam. It is crucial to explore the failure and instability characteristics and mechanism of coal–rock parting–coal structure (CRCS) in order to prevent rockburst occurrences. The following four points are addressed: (1) The failure and instability of the CRCS involve slip and fracture characteristics, which are influenced by factors such as the strength of the coal and rock parting, inclination angle, friction coefficient, and surrounding rock pressure. (2) The failure and instability of the CRCS encompass fracture instability (FI), single and double contact surface slip and fracture instability (SSI and DSI). Rockburst manifests as strain instability in the form of FI, along with structural instability in the form of SSI and DSI. (3) Crack development is primarily characterized by shear cracks supplemented by tensile cracks. However, it is the connecting effect of tensile cracks that serves as a primary cause for macro-instability within the CRCS. (4) A larger inclination angle on the contact surface results in more pronounced slip phenomena, leading to greater energy release. This demonstrates low strength but high release energy characteristics, making it difficult to predict rockburst occurrences. The research results have important theoretical significance for preventing rockburst in the bifurcation area of coal seam.

To explore the precursory characteristics and influencing factors of rockburst in the bifurcation area of coal seam, the evolution and expansion of fracture and the energy accumulation and dissipation characteristics of coal-rock parting-coal structure (CRCS) during failure and instability process are explored from a micro-scopic perspective, and the influence of coal and rock parting parameters on the instability is studied. The following four points are addressed: (1) Compared with the single coal structure or the coal- rock combined structure, the CRCS can more directly reflect the geological structure characteristics of the coal seam in the bifurcated area; (2) The failure and instability process of CRCS includes two types of instability: slip and fracture. The slip instability is characterized by low strength and high energy release, which is very difficult to predict. (3) Before the failure of CRCS, there are several precursor signal characteristics, such as the shortened development time of the "stable-fracture-stable" cycle, abnormal slip dislocation of the contact surface, and rapid accumulation of rock fracture energy. (4) The inclination angle of the contact surface affects the instability form, the strength of the rock parting affects the instability state, and the thickness of the rock parting affects the impact tendency. The research results have important theoretical significance for preventing rockburst caused by failure and instability in bifurcated area of coal seam.

The extraction of extremely thick coal seams through slicing mining requires leaving behind several island coal pillars in the top slicing, which could lead to rockburst in the bottom slicing. This article proposed a method of alternate exterior entry (AEE) for rockburst prevention based on the stress distribution of bottom slicing. The influences of coal pillar width ( B ) and stress concentration factor ( K ) on stress distribution were explored using two-dimensional stress imaging. The results indicated that K value had a greater effect on stress distribution comparing with B value. Both stress relaxed and stress rate angles increased linearly with an increase in K value. In order to get the optimized location of AEE in the coal mine stress rate angle was chosen as the stress extension angle, which was further verified by field data from 1210 coal faces. Finally, numerical simulation was used to explore the optimized location of special tail entry under dip island coal pillars for rockburst prevention. It was revealed that plan first was found to be most effective due to its presence in a stress-relaxed area, thus verifying the effectiveness of the AEE method for rockburst prevention.

Abstract The rheological characteristics of debris flow are the basis of the analysis of debris flow initiation, migration and deposition process. In order to explore the rheological characteristics of debris flow mud, according to the shear characteristics of debris flow fluid in different stages, taking Nanyang expansive soil mud as experimental material and using mcr702 rheometer blade rotor system, rheological experiments (twice increasing shear and once decreasing shear) were carried out on mud with different solid volume concentrations. According to the experimental results, the effects of different experimental processes and solid volume concentration on mud rheological parameters are analyzed, and the following conclusions are obtained: In the process of increasing shear rate, when the shear rate is less than 0.002s-1, the first shear stress is lower than the second shear stress; However, the first shear stress is higher than the second shear stress if the shear rate exceeds 0.002s-1. When the shear rate is greater than 1.83s-1, the mud is in the stable flow stage, the shear stress has a power-law relationship with the shear rate, and its rheological parameters increase exponentially with the volume concentration of mud. In the process of decelerating shear, the shear stress decreases in power law with the decrease of shear rate, which is a group of parallel lines in the double logarithmic coordinate system. Its flow index is less affected by solid volume concentration. The static yield stress of mud (the peak shear stress of the first increasing speed) is much larger than the stable flow yield stress (the shear stress value corresponding to the critical shear rate of 1.83s-1), and the difference decreases with the decrease of the volume concentration of mud solids. The static yield stress and steady flow yield stress of mud increase exponentially with the volume concentration of solid.

Currently, the research on the slip instability of rock mass structural planes has not considered the unloading effect during heading. There is relatively little research on the anisotropic structural planes of coal and rock. In order to explore the conditions and influencing factors that trigger the slip of anisotropic structural planes of coal and rock, a mechanical model of anisotropic structural planes is established. A criterion for unlocking slip of anisotropic structural planes under unloading is theoretically derived. A smooth structural plane numerical model is established using universal distinct element code (UDEC) to verify the accuracy of theoretical analysis of the triggering conditions for unlocking the slip of anisotropic structural planes. The influencing factors of unlocking slip of anisotropic structural planes are analyzed. The research results indicate that unlocking slip of anisotropic structural planes of coal and rock is related to the inclination angle of structural planes, internal friction angle, and the ratio of horizontal stress to axial stress. When the horizontal stress is equal to the axial stress, the anisotropic structural plane is always in a locked state without slipping. Increase of axial pressure and horizontal pressure and decrease of internal friction angle will increase the difficulty of unlocking slip on anisotropic structural planes. For downward unlocking slip, when the inclination angle of the structural plane is less than \begin{document}$45^\circ + \dfrac{{{\varphi _{\rm{f}}}}}{2}$\end{document} (\begin{document}$\varphi _{\rm{f}} $\end{document} is internal friction action), its increase will increase the difficulty of unlocking slip. When it is more than \begin{document}$45^\circ + \dfrac{{{\varphi _{\rm{f}}}}}{2}$\end{document}, its increase will reduce the difficulty of unlocking slip. For upward unlocking slip, when the inclination angle of the structural plane is less than \begin{document}$45^\circ - \dfrac{{{\varphi _{\rm{f}}}}}{2}$\end{document} , its increase will increase the difficulty of unlocking slip. When it is more than \begin{document}$45^\circ - \dfrac{{{\varphi _{\rm{f}}}}}{2}$\end{document}, its increase will reduce the difficulty of unlocking slip. For the locked state of structural plane, when the inclination angle of the structural plane is no more than 30°, if the axial stress is greater than the compressive strength, the brittle failure will occur in coal rock combination.

锆石是岩石中常见的副矿物,锆石晶体结构和地球化学特征的变化可以记录热液蚀变过程.东秦岭东段白草垛花岗伟晶岩中识别出三种类型锆石.类型一锆石具有明显的振荡环带,部分锆石边部有少量裂隙,微量元素含量相对较低,重稀土元素(HREE)富集,具明显Ce的正异常和Eu的负异常,指示其为岩浆锆石.类型二锆石具核-幔-边结构,边部裂隙发育,核部与类型一锆石具有相似的CL和微量元素特征,为岩浆锆石;幔部呈深色海绵状,内部结构不均匀,偶见环带锆石残留,微量元素含量较高,具有较高的U和Th含量,Ce异常不明显,具热液锆石特征,为热液沿着裂隙进入锆石内部不完全热液改造的结果.类型三锆石的结构特征和微量元素含量与类型二锆石的幔部相似,具有异常高U和Th含量以及较高的Dα值,为类型二锆石近完全热液改造的结果.花岗伟晶岩作为岩浆演化晚期的产物,经过结晶分异,残留的岩浆热液富集微量元素,岩浆热液沿着锆石的裂隙进入晶体内部对锆石经过不同程度热液改造,形成了花岗伟晶岩中不同类型的锆石.

东秦岭东段五垛山大型花岗岩基中花岗伟晶岩丰富,关于它的形成时代、岩石成因和地球动力学背景仍不清楚.LA-ICP-MS锆石U-Pb同位素定年结果显示五垛山花岗伟晶岩的年龄可分为3组:417.4±2.5 Ma,这组为花岗伟晶岩的结晶年龄,与东秦岭造山带花岗伟晶岩的形成时代相一致;429.5±2.1 Ma和 450.9±3.3 Ma,这两组与五垛山花岗岩基的年龄相一致,为花岗伟晶岩脉捕获围岩锆石的年龄.花岗伟晶岩中417.4 Ma、429.5 Ma和450.9 Ma这3组锆石的εHf(t)值分别为-5.6～-1.9、-8.7～-1.3和-5.3～-3.4,与秦岭岩群部分熔融形成岩浆岩的Hf同位素值近似.以上显示,五垛山花岗伟晶岩可能来自于秦岭岩群的部分熔融.早泥盆世,东秦岭处于原特提斯后碰撞阶段,后碰撞阶段的拉张作用使地幔减压部分熔融形成镁铁质岩浆,这些镁铁质岩浆底侵下地壳变质基底,使其部分熔融形成花岗伟晶岩的原生岩浆,这些岩浆沿着后碰撞拉张作用形成的通道上侵形成了五垛山花岗伟晶岩脉.

The yield stress of mud is the basis for analyzing the flow and desilting of debris flow. Nanyang expansive soil mud was used as experimental materials, and the rheological curves of mud with different solid volume concentrations were obtained by using the stress scanning rheological experiment of Antonpa mcr702 rheometer. For Nanyang expansive soil slurry with different solid volume concentration, the change process of shear stress with shear rate is analyzed. According to the experimental results, the rheological process of Nanyang expansive soil slurry is divided into three stages: stress growth, stress attenuation and stress stability. The slurry concentration has obvious influence on the dynamic and static shear stress of mud.

东昆仑东段哈图地区稀土元素富集与正长花岗岩关系密切.LA-ICP-MS锆石U-Pb同位素定年结果显示哈图正长花岗岩的结晶年龄为251.6±1.3 Ma.哈图正长花岗岩富硅(SiO2=74.78％～75.78％)和碱(Na2 O+K2 O=7.68％～8.11％),低铝(Al2 O3=12.58％～13.06％),铝饱和指数A/CNK介于0.96～1.03之间,主体为准铝—弱过铝质中钾钙碱性系列.哈图正长花岗岩富集轻稀土元素,亏损重稀土元素,具较明显的Eu负异常(δEu=0.67～0.91);微量元素富集Rb、Th、Ba、Cs等大离子亲石元素(LILE),亏损Nb、Ta、Ti等高场强元素(HFSE),具有较低的Nb/Ta比值和较高的Mg#值.以上显示,哈图正长花岗岩具壳源特征,为镁铁质岩浆底侵下地壳,使其部分熔融形成的原生岩浆再经过分异形成.哈图正长花岗岩具弧岩浆岩地球化学特征,结合东昆仑造山带岩浆岩分布以及沉积地层特征显示,早三叠世东昆仑地区处于布青山-阿尼玛卿洋的俯冲阶段,大规模的岩浆事件引起东昆仑造山带东段稀土元素成矿作用.

The yield stress of mud is one key to analyze the initiation and deposition of debris flow. Taking Chengdu clay as the experimental material, slurries with different solid volume concentrations were prepared. Using the blade rotor system of mcr301 rheometer and the continuous shear experimental method, the dynamic change process of shear stress of slurries with different solid volume concentrations was obtained with the shear rate increasing and decreasing continuously. According to the experimental results, the static and dynamic yield stress of Chengdu clay slurry is determined, and the influence of solid volume concentration on the yield stress is analyzed. The following conclusions are obtained: Chengdu clay slurry is a non-Newtonian fluid with yield stress. In the process of accelerated shear, for Chengdu clay slurry with solid volume concentration exceeding 35%, the shear rate is in the range of 0.01–1 s −1 , and the shear stress increases rapidly to the maximum. When the shear rate exceeds 1 s −1 , the shear stress decreases rapidly and finally tends to be stable. The shear rate appears stress overshoot near 1s −1 . However, in the process of increasing shear rate, for Chengdu clay slurry with solid volume concentration of no more than 35%, the shear stress increases rapidly in the range of shear rate of 0.01–0.1 s −1 , and the shear rate exceeds 0.1 s −1 . The shear rate has little effect on the shear stress, and the stress overshoot disappears. In the process of deceleration shear, for all solid volume concentrations in the semi logarithmic coordinate system, the mud shear stress decreases steadily with the decrease of shear rate. The static and dynamic yield stress of slurry increases exponentially with particle concentration.

Some of the fundamental properties of nanofluids capable of influencing not only the transport phenomena, but also mass and heat transfer within the boundary layer and throughout the domain are thermo-migration and random mobility of nanoparticles in the based fluid. In such a case mentioned above, nothing is known on a comparative ternary-hybrid nanofluid flows induced by forced convection, free convection, and mixed convection when radiative heat flux is substantially regulated by temperature difference as in the case of non-linear thermal radiation, and partial slip. This report presents the similarity solutions of the governing equations that models the dynamics of colloidal mixture of water with spherical carbon nanotubes, cylindrical graphene, and platelet alumina nanoparticles at different levels of partial slip considering the cases of forced, free and mixed convection. The shooting approach was used in conjunction with the conventional Runge-Kutta integration scheme and MATLAB bvp4c to get solutions of the emerged boundary value problems. The outcome of the study shows that the friction at the wall decreases with partial slip but the most minimum decreasing rate manifests at the higher level of buoyancy forces when the transport phenomenon was induced by free convection. Optimal increasing transfer rates of mass/species is achievable due to rising haphazard motion of the three kinds of nanoparticles when the ternary-hybrid nanofluid was induced by mixed convection. Rising thermo-migration of spherical carbon nanotubes, cylindrical graphene, and platelet alumina nanoparticles causes the transfer of species and heat across the ternary-hybrid nanofluid to diminish.

The determination of rheological model about the debris flow is the basis of the simulation of mud flow impact distance and sedimentary fan. By using a mcr301 rheometer, rheological experiments of Chengdu clay slurry with different solid volume concentrations were carried out and the effect of solid volume concentration on shear stress were analyzed. Then the rheological process of Chengdu clay slurry with different solid volume concentration was fitted on the basis of the power law model, the Bingham model and the H–B model. The conclusions are drawn as follows: Chengdu clay mud is a typical shear-thinning non-Newtonian body. The influence of solid concentration on the flow curve is different. When the solid volume concentration is not less than 34% and the shear rate is less than 1.0 s−1, the shear stress increases rapidly as the shear rate increases. Meanwhile, when the shear rate is greater than 1.0 s−1 the shear stress decreases with the increase in the shear rate. When the solid volume concentration is less than 31.6% and the shear rate is less than 1.0 s−1, the shear stress increases with the increase in the shear rate, while when the shear rate is more than 1.0 s−1, the shear stress is less affected by shear rate. In the range of low shear rate (less than 1.0 s−1), the increase amplitude of shear stress (slope of semi logarithmic coordinate flow curve) increases as the solid volume content increases. The flow curve of Chengdu clay mud can be reflected in the whole process by using the Herschel and Bulkley model. It is the best mathematical model to fit the rheological process of Chengdu clay mud. According to the above results, the effect of solid volume concentration on the yield stress of the H–B model is analyzed.

泥浆是泥石流动力学的重要研究对象.细小的黏性颗粒是黏性泥石流泥浆的基本组成部分,传统流变模型可以描述粘性泥石流中颗粒物质相互作用,然而各灾害点物质组成的差异性使得泥浆流变模型的应用各有不同,且当前研究缺少对不同模型应用的详细讨论.本研究利用MCR301流变仪,开展不同含水量成都粘土泥浆流变实验,分析成都粘土泥浆剪切应力随剪切速率变化过程、含水量对剪切应力的影响;对比分析幂律模型、宾汉模型和Herschel&Bulkley模型(H-B模型),拟合各含水量成都粘土泥浆的流变实验结果.得出如下结论:(1)随着含水量由50％增大到400％,成都粘土泥浆切应力迅速降低,由超过8000 Pa降低到5 Pa左右;当剪切速率约为0.2 s-1时,剪切应力随剪切速率增加而迅速增大,但当剪切速率大于0.2 s-1时,剪切应力随剪切速率增加而增长缓慢,成都粘土泥浆表现出典型的剪切稀化非牛顿体流体;(2)H-B模型能很好地反映各含水量成都粘土泥浆剪切应力与剪切速率的变化全过程(剪切稀化),是拟合成都粘土泥浆流变过程的最佳数学模型;(3)泥浆屈服应力(τHB)和流动指数(ηHB)随含水量的增加迅速减小.本文流变模型实验的开展和研究对深入认知和探索泥石流致灾全过程具有重要意义.

以污泥含水率(WC)、离心沉降比(CSE)和毛细吸水时间(CST)为脱水性能评价指标,利用超声波、Fenton协同PAM对城市污泥进行处理,探讨脱水性能改善效果及机理.在单因素实验的基础上,以响应曲面优化法(RSM)为手段,建立二次多项预测模型方程,进行方差分析,得到最佳处理参数.结果表明,超声波、Fenton和PAM三因素耦合处理最佳值分别为:126 s、0.12 mL·mL-1和0.3 mg·mL-1;该处理条件下,污泥滤饼含水率(WC)和离心沉降比(CSE)分别为(70.5±0.25)％和(23±0.31)％,与模型方程预测值基本一致;污泥毛细吸水时间(CST)减小率为82.3％;热重分析(TG-GTG)表明失重温度前移,激光粒度分析证实污泥颗粒最大粒径从1000μm增加到3500μm,比表面积减小率为43.97％;三因素耦合处理使污泥更容易絮凝成粒径更大的颗粒.

Slip and instability of coal-rock parting-coal structure (CRCS) subjected to excavation disturbance can easily induce coal-rock dynamic phenomena in deep coal mines. In this paper, the failure characteristics and influencing factors of CRCS slip and instability were investigated by theoretical analysis, numerical simulations, and field observations. The following main results are addressed: (1) the slip and instability of CRCS induced by excavation are due to stress release, and the damage of the rock parting is partitioned into three parts: shear failure zone, slipping zone, and splitting failure zone from inside to outside with slip; (2) the slip and instability process of CRCS is accompanied by initiation, expansion, and intersection of shear and tensile cracks. The development of the cracks is dominated by shear behaviour, while the tensile crack is the main factor affecting fracture and instability of CRCS; and (3) slip and instability of CRCS are characterized by stick-slip first and then stable slip, accompanied with high P-wave velocity and rockburst danger coefficient based on microseismic tomography.

巷道随开采深度的增加,其围岩变形会逐渐增大,特别是深部巷道.本文采用FLAC3D软件,分析深部巷道的掘进过程中围岩变形规律及应力分布.研究表明:巷道开挖后,顶板会产生了高达144 mm的下沉变形量,底部产生了将近15 mm拱起变形量,两帮偏移量高达208 mm;围岩应力会产生二次分布,其中顶底部会产生最大0.12 MPa的拉应力,两帮会产生最大0.04 MPa的拉应力.因此,需及时采取巷道围岩加固措施,防止围岩产生进一步的变形.