Control effect and optimization scheme of combined rockbolt-cable support for a tunnel in horizontally layered limestone:A case study

This study focused on the mechanical behavior of a deep-buried tunnel constructed in horizontally layered limestone,and investigated the effect of a new combined rockboltecable support system on the tunnel response.The Yujingshan Tunnel,excavated through a giant karst cave,was used as a case study.Firstly,a multi-objective optimization model for the rockboltecable support was proposed by using fuzzy mathematics and multi-objective comprehensive decision-making principles.Subsequently,the parameters of the surrounding rock were calibrated by comparing the simulation results obtained by the discrete element method(DEM)with the field monitoring data to obtain an optimized support scheme based on the optimization model.Finally,the optimization scheme was applied to the karst cave section,which was divided into the B-and C-shaped sections.The distribution range of the rockboltecable support in the C-shaped section was larger than that in the B-shaped section.The field monitoring results,including tunnel crown settlement,horizontal convergence,and axial force of the rockboltecable system,were analyzed to assess the effectiveness of the optimization scheme.The maximum crown settlement and horizontal convergence were measured to be 25.9 mm and 35 mm,accounting for 0.1%and 0.2%of the tunnel height and span,respectively.Although the C-shaped section had poorer rock properties than the B-shaped section,the crown settlement and horizontal convergence in the C-shaped section ranged from 46%to 97%of those observed in the B-shaped section.The cable axial force in the Bshaped section was approximately 60%of that in the C-shaped section.The axial force in the crown rockbolt was much smaller than that in the sidewall rockbolt.Field monitoring results demonstrated that the optimized scheme effectively controlled the deformation of the layered surrounding rock,ensuring that it remained within a safe range.These results provide valuable references for the design of support systems in deep-buried tunnels situated in layered rock masses.

Experimental study on the bolt–cable combined supporting technology for the extraction roadways in weakly cemented strata

Aiming at the characteristics of the poor steady ability, the short stable time and severe deformation behavior of weakly cemented soft surrounding rock around extraction roadway, a bolt–cable combined supporting technology was proposed. Numerical simulation was performed by using FLAC3 D software to study the effects of different supporting systems. The simulation result proves that those supporting systems have good practical values. Based on real-time monitoring and analysis of the deformation of surrounding rock and the stress of supporting structure, real time information of deformation of surrounding rock and stress state of supporting structure of extraction roadway within weakly cemented strata was obtained. Monitoring results show that large deformation and failure of surrounding rock of extraction roadway within weakly cemented strata can be effectively controlled by the bolt–cable combined supporting technology, which ensures the long-term stability and safety of surrounding rock and supporting structure.

Combined blasting for protection of gob-side roadway with thick and hard roof

The deformation control of surrounding rock in gobside roadway with thick and hard roof poses a significant challenge to the safety and efficiency of coal mining.To address this issue,a novel approach combining directional and non-directional blasting techniques,known as combined blasting,was proposed.This study focuses on the experimental investigation of the proposed method in the 122108 working face in Caojiatan Coal Mine as the engineering background.The initial phase of the study involves physical model experiments to reveal the underlying mechanisms of combined blasting for protecting gob-side roadway with thick and hard roof.The results demonstrate that this approach effectively accelerates the collapse of thick and hard roofs,enhances the fragmentation and expansion coefficient of gangue,facilitates the filling of the goaf with gangue,and provides support to the overlying strata,thus reducing the subsidence of the overlying strata above the goaf.Additionally,the method involves cutting the main roof into shorter beams to decrease the stress and disrupt stress transmission pathways.Subsequent numerical simulations were conducted to corroborate the findings of the physical model experiments,thus validating the accuracy of the experimental results.Furthermore,field engineering experiments were performed,affirming the efficacy of the combined blasting method in mitigating the deformation of surrounding rock and achieving the desired protection of the gob-side roadway.

Classification of power quality combined disturbances based on phase space reconstruction and support vector machines

Power Quality (PQ) combined disturbances become common along with ubiquity of voltage flickers and harmonics. This paper presents a novel approach to classify the different patterns of PQ combined disturbances. The classification system consists of two parts, namely the feature extraction and the automatic recognition. In the feature extraction stage, Phase Space Reconstruction (PSR), a time series analysis tool, is utilized to construct disturbance signal trajectories. For these trajectories, several indices are proposed to form the feature vectors. Support Vector Machines (SVMs) are then implemented to recognize the different patterns and to evaluate the efficiencies. The types of disturbances discussed include a combination of short-term dis-turbances (voltage sags, swells) and long-term disturbances (flickers, harmonics), as well as their homologous single ones. The feasibilities of the proposed approach are verified by simulation with thousands of PQ events. Comparison studies based on Wavelet Transform (WT) and Artificial Neural Network (ANN) are also reported to show its advantages.

Combined support mechanism of rock bolts and anchor cables for adjacent roadways in the external staggered split-level panel layout

Using the spatial structure of the external staggered split-level panel layout,a combined support technology for adjacent roadways was developed and analyzed for a rock bolt and anchor cable mechanism.The influence of the side rock bolt and anchor cable parameters on the mechanical properties of the anchorage body and the support stress distribution of the lateral coal body were revealed using the FLAC3D software.The optimal support parameters of the side rock bolts and anchor cables were subsequently determined,and the support effect of gob-side entry in a mining scenario was verified.The results show that the support of the side rock bolts and anchor cables improves the mechanical properties and stress state of the anchorage body,producing a good protective effect on the coal body of the air-intake entry roof and side wall.This is beneficial to the stability of the side wall and the realization of the suspension effect for roof rock bolts and anchor cables,which in turn makes the surrounding rock maintenance of the gob-side entry to a thick coal seam more favorable.

New perspectives and prospects for the next generation of combination therapy in inflammatory bowel disease

This article comments on the letter by Lowell et al,which addresses the next generation of combination therapy for inflammatory bowel disease(IBD).As the understanding of the pathogenesis of IBD continues to improve,treatment strategies are evolving rapidly.The letter examines the current status and future directions of combination therapy for IBD,focusing on approaches that combine biologics with immunomodulators and the emerging dual-biologic therapy(DBT).The traditional combination of biologics and immunomodulators has demonstra-ted preliminary efficacy by enhancing the effects of biologics through immunomo-dulation.However,concerns regarding long-term safety warrant careful evalua-tion.Recent trials,including DUET-Crohn's disease and DUET-ulcerative colitis,have shown promising potential for the broader adoption of DBT.Nevertheless,comprehensive data on efficacy and safety,as well as the effective integration of supportive treatments,remain essential to establish new paradigms for the next generation of IBD care.

A new spatial coherence model and analytical coeffi cients for multi-support response spectrum combination

In this paper, a new spatial coherence model of seismic ground motions is proposed by a fitting procedure. The analytical expressions of modal combination （correlation） coefficients of structural response are developed for multi-support seismic excitations. The coefficients from both the numerical integration and analytical solutions are compared to verify the accuracy of the solutions. It is shown that the analytical expressions of numerical modal combination coefficients are of high accuracy. The results of random responses of an example bridge show that the analytical modal combination coefficients developed in this paper are accurate enough to meet the requirements needed in practice. In addition, the computational efficiency of the analytical solutions of the modal combination coefficients is demonstrated by the response computation of the example bridge. It is found that the time required for the structural response analysis by using the analytical modal combination coefficients is less than 1/20 of that using numerical integral methods.

Online Fault Prediction Based on Combined AOSVR and ARMA Models

Accurate fault prediction can obviously reduce cost and decrease the probability of accidents so as to improve the performance of the system testing and maintenance. Traditional fault prediction methods are always offline that are not suitable for online and real-time processing. For the complicated nonlinear and non-stationary time series, it is hard to achieve exact predicting result with single models such as support vector regression （SVR）, artifieial neural network （ANN）, and autoregressive moving average （ARMA）. Combined with the accurate online support vector regression （AOSVR） algorithm and ARMA model, a new online approach is presented to forecast fault with time series prediction. The fault trend feature can be extracted by the AOSVR with global kernel for general fault modes. Moreover, its prediction residual that represents the local high-frequency components is synchronously revised and compensated by the sliding time window ARMA model. Fault prediction with combined AOSVR and ARMA can be realized better than with the single one. Experiments on Tennessee Eastman process fault data show the new method is practical and effective.

Development of multi-functional anchorage support dynamic-static coupling performance test system and its application

In underground engineering with complex conditions,the bolt(cable)anchorage support system is in an environment where static and dynamic stresses coexist,under the action of geological conditions such as high stresses and strong disturbances and construction conditions such as the application of high prestress.It is essential to study the support components performance under dynamic-static coupling conditions.Based on this,a multi-functional anchorage support dynamic-static coupling performance test system(MAC system)is developed,which can achieve 7 types of testing functions,including single component performance,anchored net performance,anchored rock performance and so on.The bolt and cable mechanical tests are conducted by MAC system under different prestress levels.The results showed that compared to the non-prestress condition,the impact resistance performance of prestressed bolts(cables)is significantly reduced.In the prestress range of 50–160 k N,the maximum reduction rate of impact energy resisted by different types of bolts is 53.9%–61.5%compared to non-prestress condition.In the prestress range of 150–300 k N,the impact energy resisted by high-strength cable is reduced by76.8%–84.6%compared to non-prestress condition.The MAC system achieves dynamic-static coupling performance test,which provide an effective means for the design of anchorage support system.

Combined transplantation of GDAs^(BMP) and hr-decorin in spinal cord contusion repair

Following spinal cord injury, astrocyte proliferation and scar formation are the main factors inhibiting the regeneration and growth of spinal cord axons. Recombinant decorin suppresses inflammatory reactions, inhibits glial scar formation, and promotes axonal growth. Rat models of T8 spinal cord contusion were created with the NYU impactor and these models were subjected to combined transplantation of bone morphogenetic protein-4-induced glial-restricted precursor-derived astro- cytes and human recombinant decorin transplantation. At 28 days after spinal cord contusion, dou- ble-immunofluorescent histochemistry revealed that combined transplantation inhibited the early in- flammatory response in injured rats. Furthermore, brain-derived neurotrophic factor, which was se- creted by transplanted cells, protected injured axons. The combined transplantation promoted ax- onal regeneration and growth of injured motor and sensory neurons by inhibiting astrocyte prolif- eration and glial scar formation, with astrocytes forming a linear arrangement in the contused spinal cord, thus providing axonal regeneration channels.

Tall gastrodis tuber combined with antiepileptic drugs repairs abnormal perfusion foci in focal epilepsy

One hundred patients with focal epilepsy were recruited for the present study and their seizures controlled with antiepileptic drugs. The patients then orally received a capsule of tall gastrodis tuber powder, a traditional Chinese drug, and underwent single photon emission computed tomography, long-term electroencephalogram, and CT/MRI. Blood drug levels were monitored throughout the study. Before treatment with tall gastrodis tuber, 35 of the 100 cases had abnormal CT/MRI scans; 79 cases had abnormal single photon emission computed tomography images; 86 cases had abnormal electroencephalogram; and a total of 146 abnormal perfusion foci were observed across the 100 subjects. After treatment, the number of patients with normal single photon emission computed tomography images increased by 12; normal electroencephalogram was observed in an additional 27 cases and the number of patients with epileptiform discharge decreased by 29 （34% of 86）; the total number of abnormal perfusion foci decreased by 52 （36%） and changes in abnormal loci were visible in 65 patients. These changes indicate that the administration of tall gastrodis tuber in combination with antiepileptic drugs repairs abnormal perfusion foci in patients with focal epilepsy Our results demonstrate that traditional Chinese drugs can repair abnormal perfusion foci and, as such, are a promising new pathway in the treatment of focal epilepsy.

高精度惯量积测量的支撑结构设计研究

针对惯性仪表组件高精度惯量积测量中的无干扰力矩支撑方式需求,设计了径向气浮和轴向气浮相结合的组合气体轴承作为非接触支撑结构.为了研究支撑结构的承载能力,建立其理论模型,结合计算流体力学进行仿真,同时设计并搭建试验装置验证仿真的准确性.研究表明仿真与试验结果相近,并且发现非接触支撑结构的轴向承载力是惯量积测量时的薄弱处,结合参数化建模开展了轴向承载力提升研究.结果表明:增大支撑结构中的转子套筒大径有利于提高轴向承载力;结构改进后,轴向承载力提升182.98%,惯量积测量时的旋转速度上限提升54.10%,测量精度提升42.11%.

基于可编程逻辑控制器的煤矿综采组合开关结构设计

针对有效、统一控制煤矿综采工作面多种采煤设备为目的,设计基于可编程逻辑控制器的煤矿综采工作面配套组合开关结构。该开关结构分为主控制电路、次控制电路,两种电路均与液晶显示模块相连。通过液晶显示模块的界面将电路状态反馈给管理人员,两种控制电路主要通过可编程逻辑控制器和继电器、信号提醒、保护回路相连,分别完成电源供应、警报信息提醒、采煤设备连接状态管理。实验结果表明,在过载、漏电工况中可用电气互锁的方式保证采煤机状态不出现异常变化,完成异常采煤设备的统一管理,最高节能比例达到11.2%,最低节能比例也能达到7.8%,由此证明设计的方法具有一定研究价值。

组合支护式深基坑开挖数值模拟及影响因素分析

以某桩锚桩撑组合支护的基坑工程为依托,通过MIDAS GTS NX有限元软件对基坑开挖过程进行还原模拟,同时探究桩锚桩撑所占比例的变化对基坑支护结构变形的影响。模拟结果表明:随着桩锚支护所占比例的增加,支护结构变形与锚杆轴力均逐渐增大并趋于稳定,但是内支撑轴力则呈现出逐渐减小的变化趋势。

综采工作面端面破碎支护技术应用分析

平泉煤矿15109工作面过断层应力区,面临煤壁垮落严重、局部端面冒漏、支架载荷大等技术难题;从围岩应力、支护方式以及煤层结构等方面分析端面破碎原因,拟对端面破碎围岩采用“超前管棚注浆+柔性纤维网+玻璃钢锚棚+人工假顶”联合支护技术;新支护技术应用后,控制了断层应力区围岩破碎现象,减小了端面冒漏范围,后期工作面回采中煤壁最大片帮长度不足1.5 m,片帮深度不足0.6 m,最大端面距为0.37 m,取得了显著应用成效。

断层应力下巷道围岩支护技术应用

针对宁武榆树坡煤业5106运输巷道过断层破碎带时围岩变形大、控制困难的问题,通过现场勘察和数值模拟,分析了围岩应力环境和破坏机理,得出构造应力大、围岩破碎、岩性差,支护方案失效导致围岩变形破坏严重。据此提出了“喷射混凝土+注浆+锚网索”联合支护方案。现场工业试验表明,该支护方案后,巷道顶板、底板及两帮最大变形量分别为138 mm、113 mm和164 mm,巷道整体加固效果好,表面平整,无混凝土开裂、锚杆索断裂现象。

综采面端头煤柱破碎条件下的联合支护分析

马脊梁矿8109工作面回采期间尾端头三角煤柱垮落严重,导致端头悬顶面积大、端头之间出现压架现象,以及尾顺槽超前应力区内顶板破碎下沉、底板鼓起等;从集中应力、支护工艺、煤层赋存等方面分析了8109工作面尾端头三角煤柱垮落原因;拟定采用“钻孔卸压+注浆加固+水力膨胀锚杆+可移式伸缩支架”等联合支护技术;应用表明,采取联合控制技术后,尾端头三角煤柱垮落长度减小至0.5 m,超前应力区范围内回风顺槽顶板最大下沉量减小为0.16 m,最大底鼓量减小为0.24 m,两帮最大收敛量减小为0.27 m。

掘进巷道过陷落柱围岩控制技术研究

针对掘进巷道过陷落柱期间围岩变形量大、支护困难和顶板淋水严重的问题,以华阳一矿81214回风巷为研究对象,采用理论分析和现场试验的研究方法,对过陷落柱期间巷道围岩特征和巷道原支护存在的问题进行分析,提出了“超前注浆+顶板全锚索+双层金属网+喷浆”的掘进巷道过陷落柱围岩综合控制措施。现场试验结果表明:采用综合控制措施后,过陷落柱段巷道顶底板最大下沉量为41.64 mm,巷帮最大位移量为20.31 mm,围岩变形控制效果显著,确保了巷道稳定性和工作面生产安全。

斜撑贝雷梁组合支架研发及其在跨浅埋地铁现浇箱梁中的应用

高架结构在既有交通线路上方进行现浇梁施工时,将对线路的正常运行产生扰动,软土地质的存在将会进一步加剧此类影响。为解决类似技术难题,文章结合在建的上海松江高铁南站简支箱梁施工工程实例,设计一种可跨越既有交通线路直接施工的新型支架体系——斜向支撑体系与贝雷梁组合支架。结合支架部件组成及实际施工过程出现的荷载工况,通过MIDAS Civil有限元分析软件建模分析支架的应力及位移,确保支架在施工过程中的受力安全、结构稳定。结果表明,设计的斜撑贝雷梁支架结构,能在不影响既有线路运行的情况下进行施工,支架结构强度、刚度及稳定性均能满足规范要求,可为同类型桥梁的支架设计、计算提供可行性思路。

Support technologies for deep and complex roadways in underground coal mines:a review

Based on geological and mining characteristics,coal mine roadways under complex conditions were divided into five types,for each type the deformation and damage characteristics of rocks surrounding roadways were analyzed.The recent developments of roadway support technologies were introduced abroad,based on the experiences of supports for deep and complex roadways from Germany,the United States and Australia.The history and achievements of roadway support technologies in China were detailed,including rock bolting,steel supports,grouting reinforcement and combined supports.Four typical support and reinforcement case studies were analyzed,including a high stressed roadway 1,000 m below the surface,a roadway surrounded by severely weak and broken rocks,a chamber surrounded by weak and broken rocks,and a roadway with very soft and swelling rocks.Based on studies and practices in many years,rock bolting has become the mainstream roadway support form in China coal mines,and steel supports,grouting reinforcement and combined supports have also been applied at proper occasions,which have provided reliable technical measures for the safe and high effective construction and mining of underground coal mines.