Study on Asymmetric Deformation Law and Surrounding Rock Control Technology of High Stress Soft Rock Crossing Roadway

In order to solve the problem of asymmetric large deformation of high-stress soft rock crossing roadway under complex geological conditions in deep mines, taking the 2# total return airway of 76.2# section of Wuyang Coal Mine as the engineering background, the causes of asymmetric deformation and failure of soft rock crossing roadway in deep mines were summarized and analyzed by means of field investigation, theoretical analysis and numerical simulation, and the asymmetric high-efficiency support technology with large row spacing was studied. The results show that the lithology of roadway strata is the main cause of asymmetric deformation and failure of roadway. The shape change of roadway is not the main influencing factor of asymmetric deformation of roadway, but for the control of roadway surrounding rock, the straight wall semi-circular arch roadway is better than the rectangular roadway. The field industrial test shows that after adopting the new support design scheme, the displacement of the roof and floor of the roadway is reduced by 86.39% compared with the original support design scheme, and the displacement of the two sides of the roadway is reduced by 86.05% compared with the original support design scheme, which can ensure the normal and safe production of the roadway during the service period, and provide reference for the support design of other similar geological conditions.

Failure mechanism of bolting support and high-strength bolt-grouting technology for deep and soft surrounding rock with high stress

In deep underground mining, the surrounding rocks are very soft with high stress. Their deformation and destruction are serious, and frequent failures occur on the bolt support. The failure mechanism of bolt support is proposed to solve these problems. A calculation theory is established on the bond strength of the interface between the anchoring agent and surrounding rocks. An analysis is made on the influence law of different mechanical parameters of surrounding rocks on the interfacial bond strength. Based on the research, a new high-strength bolt-grouting technology is developed and applied on site. Besides, some helpful engineering suggestions and measures are proposed. The research shows that the serious deformation and failure, and the lower bond strength are the major factors causing frequent failures of bolt support. So, the bolt could not give full play to its supporting potential. It is also shown that as the integrity, strength, interface dilatancy and stress of surrounding rocks are improved, the bond strength will increase. So, the anchoring force on surrounding rocks can be effectively improved by employing an anchoring agent with high sand content, mechanical anchoring means, or grouting reinforcement. The new technology has advantages in a high strength, imposing pre-tightening force, and giving full play to the bolt supporting potential. Hence, it can improve the control effect on surrounding rocks. All these could be helpful references for the design of bolt support in deep underground mines.

Principle and practice of coupling support of double yielding shell of soft rock roadway under high stress

In order to ensure the safety and stability of the soft rock roadway under high stress, based on the char- acteristics of the surrounding rock deformation and failure, this paper presented the support technology“coupling support of double yielding shell”, then gave the design method of inner and outer shells and analyzed the principle and requirements of the support technology by taking the -850 meast belt mad-way of Qujiang coal mine as the background. The field application results show that the support technol- ogy can control the soft rock roadway deformation better under high stress. The displacement between roadway sides was 851 mm, the displacement of the roof was 430 mm, and the displacement of the floor was 510 mm.

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.

The principle of stability control of surrounding rock-bearing structures in high stress soft rock roadways

Through the description of the deformational features of the surrounding rockaround high stress engineering soft rock roadways,the coupling stabilization principle ofinner and outer structures in surrounding rock was put forward.The supporting principlesof high stress engineering soft rock roadway (high resistance and yielding support,timelysupport,high strength and high stiffness supports) were proposed,which were applied inengineering practices,and obtained better achievements.

An experimental study of a yielding support for roadways constructed in deep broken soft rock under high stress

A rationally designed support for deep roadways excavated in broken soft rock under high stress was investigated. The deformation and failure characteristics and the mechanism of ''yielding support'' was studied for anchor bolts and cables. The rail roadway of the 2-501 working face in the Liyazhuang Mine of the Huozhou coal area located in Shanxi province was used for field trials. The geological conditions used there were used during the design phase. The new ''highly resistant, yielding'' support system has a core of high strength, yielding bolts and anchor cables. The field tests show that this support system adapts well to the deformation and pressure in the deep broken soft rock. The support system effectively controls damage to the roadway and ensures the long term stability of the wall rock and safe production in the coal mine. This provides a remarkable economic and social benefit and has broad prospects for fur- ther application.

Engineering study on roadway support in high-stress composite soft rock

The present study is focused on the roadway support in high stress composite soft rock. This paper expounds the two main features of roadway in soft rock, i.e., great deformation of surrounding rock and remarkable rheological deformation. Furthermore, on the basis of analyzing physico chemical component of surrounding rock and the situation of the damaged roadway, the method of adopting strong bolting and shotcreting mesh for the primary support, bolting and grouting for the secondary support is put forward in light of the on the spot investigation of stress tension, mechanical parameter and engineering geology. The application reveals the method facilitates the continuation of west main roadway and the restoration of shaft station and chambers. Consequently, better techno economic results have been achieved.

Analytical investigation for stress measurement with the rheological stress recovery method in deep soft rock

Due to the difficulty and weakness of current stress measurement methods in deep soft rock, a new rheological stress recovery method of the determination of the three-dimensional(3D) stress tensor is proposed. It is supposed that rock stresses will recovery gradually with time and can be measured by embedding transducers into the borehole. In order to explore the applicability and accuracy of this method, analytical solutions are developed for stress measurement with the rheological stress recovery method in a viscoelastic surrounding rock, the rheological properties of which are depicted as both the Burger's model and a 3-parameter solid model. In such conditions, explicit analytical expressions for predicting time-dependent pressures on the transducer are derived. A parametric analysis is then adopted to investigate the influences of the grout solidification time and the mechanical properties of the grout layer. The results indicate that this method is suitable for stress measurement in deep soft rock, the characteristics of which are soft, fractured and subjected to high geo-stress.

Bolt-grouting combined support technology in deep soft rock roadway

Analyzing the mineral composition, mechanical properties and ground stress testing in surrounding rock,the study investigated the failure mechanism of deep soft rock roadway with high stress. The boltgrouting combined support system was proposed to prevent such failures. By means of FLAC3D numerical simulation and similar material simulation, the feasibility of the support design and the effectiveness of support parameters were discussed. According to the monitoring the surface and deep displacement in surrounding rock as well as bolt axial load, this paper analyzed the deformation of surrounding rock and the stress condition of the support structure. The monitor results were used to optimize the proposed support scheme. The results of field monitors demonstrate that the bolt-grouting combined support technology could improve the surround rock strength and bearing capacity of support structure, which controlled the great deformation failure and rheological property effectively in deep soft rock roadway with high stress. As a result, the long term stability and safety are guaranteed.

Optimization of construction scheme and supporting technology for HJS soft rock tunnel

For a soft rock tunnel under high stress in jointed and swell soft rock （HJS）, two construction schemes pilot-tunneling enlarging excavation and step-by-step excavation were optimized using FLAC20, and the deformation effects of the two construction schemes were verified by field tests. Based on engineer- ing geological investigation and mechanical analysis of large deformations, the complex deformation mechanisms of stress expansion and structural deformation of the soft rock tunnel were confirmed, and support countermeasures from the complex deformation mechanism converted to a single type were proposed, and the support parameters were optimized by field tests. These technologies were proved by engineering practice, which produced significant technical and economic benefits.

Study on the Deformation Mechanism of a Soft Rock Tunnel

The large deformation of soft rock tunnel is one of the key problems to be overcome in the tunnel construction stage.In the present study,the deformation mechanism of a representative tunnel and some related countermeasures are investigated using field tests and engineering geological analysis.Owing to the scarce performances of methods based on other criteria such as small pipe spacing,anchor bolt length and steel frame spacing,a new support scheme is implemented and optimized.Results show that shear failure and bedding sliding are produced under high horizontal stress conditions.The low strength of the surrounding rock results in the uneven convergence of both sides of the tunnel.With the aforementioned new support scheme,however,most of such problems can be mitigated leading to good stability properties and ensuing economic advantages.

极高地应力软岩隧道非对称变形机理及支护优化研究

针对极大断面公路隧道施工中出现的非对称大变形问题,考虑高地应力第一主应力与隧道轴线关系、层状软岩夹层与互层状态、掌子面软岩空间不对称、地下水等因素,基于对工程地质条件、围岩与支护结构失效及破坏特征的分析,结合岩样物理力学特性室内试验研究及地应力实测情况,探究了非对称大变形形成机理并提出针对性的支护结果优化方案。结果表明:高地应力层状软岩隧道围岩不对称变形是在岩层倾角α、最大水平主应力与隧道轴线夹角β和岩层夹角γ、围岩岩性和地下水综合作用下的大变形,围岩不对称部位由以上几种因素共同决定;当主应力σ1与隧道轴线既不垂直也不平行时,会产生挤压性偏压构造水平地应力,使隧道横断面侧向受力不对称,发生偏压性非对称大变形;通过改变锚杆的布设方式、提高超前注浆小导管的长度和刚度、喷射临时封闭、在防水板与喷射砼间增加高密度橡塑海绵板缓冲层等措施,可以有效的减少变形量,防止围岩因开挖扰动而松动和坍塌。

深部极松软围岩沿空巷道稳定性控制及应用

针对深部高应力作用下极松软围岩变形量大、破碎程度高、巷道难支护等问题,以丁集煤矿1232(3)沿空巷道为工程背景,采用数值模拟、现场监测和井下试验相结合的方法,对深部高应力极松软围岩沿空巷道破坏特征及阶段性控制原理和技术进行研究。结果表明:随着距巷道迎头距离的不断增大,巷道两帮应力的不对称性逐渐增大,实体煤侧应力峰值为37.18 MPa大于煤柱侧35.21 MPa,1242(3)终采线50 m范围内存在应力集中,最大达33 MPa,巷道围岩塑性区发育程度为煤柱帮大于实体煤帮大于顶底板;从巷道掘进过程中所经历的复杂围岩变化过程,将全巷道划分为5种典型的围岩变化阶段来分析围岩变形破坏特征和破坏机理,揭示了在高应力作用下深部软岩沿空巷道围岩变形量大,在空间上呈现出明显的区域性和非对称性的特征;基于巷道初步设计方案和围岩变形破坏特征,及时有效的调整支护方案,对巷道进行分段式、非对称、区域化综合治理,形成深部软岩巷道围岩控制长效机制,为同类型深部软岩巷道地压治理提供了理论和技术支撑。

高地应力软岩隧道初支侵限诱因及控制措施研究

高地应力软弱围岩隧道施工易发生软岩大变形不良地质灾害,进一步引发掌子面失稳塌方、初支结构破坏、钢拱架弯折、初支结构侵限等不良现象,严重影响施工安全,阻碍工期。依托九绵高速白马隧道工程,结合工程特点,从围岩自身力学特性及高地应力软岩变形特征方面深入分析了白马隧道初支侵限机理,并针对此特点,提出了一套适用于软岩大变形初支结构侵限专项施工方案。研究结果表明,由于地下水的侵蚀,炭质千枚岩发生软化,岩体力学性质变差,自承能力降低,在高地应力持续作用下,围岩发生挤压大变形,进一步诱导初支侵限。变更支护方案后,6 m锚杆结合小导管注浆加固对围岩变形有一定控制作用,但6 m锚杆无法将松动区岩块锚固在稳定母体中,不能充分发挥锚杆悬吊能力,对围岩变形控制效果有限,无法满足现场围岩变形需求,建议采用8 m长锚杆。初支拆换过程中应实时监测围岩变化情况,明确围岩变化方向、速率、累计值等,并根据现场实时监测数据反馈施工,实时调整支护参数,确保施工质量。

软岩筑坝技术在某面板堆石坝的应用研究

本文采用邓肯张e-b模型,使用通用岩土分析软件MIDAS GTS NX软件对大坝建立了三维模型,设计四种不同分区使用软岩的方案,分别为主体、主堆石区、次堆石区以及次堆石区510~610 m高程部分使用软岩,并对四种方案下面板堆石坝的应力与变形进行了分析。得到以下结论:采用软岩的大坝应力与变形分布规律与传统堆石料类似,在次堆石区部分部位使用软岩可以大大降低大坝的应力与变形,软岩用于高面板坝坝体填筑是安全可行的。分析结果对工程设计优化、类似工程借鉴、保证工程安全具有一定的参考价值。

深埋隧洞软岩变形控制和应力拱圈形成分析

就深埋隧洞在高地应力软岩环境应力拱圈的形成、应力拱圈的强度和围压作用,以及围岩变形控制机理进行论述。分析超前地质预报、减少围岩扰动、数学模拟及监测、主动让压支护、围岩约束平稳过渡对变形控制及应力拱圈形成的作用,以及分析主动让压支护成功案例,阐明控制围岩应力释放的同时又及时提供围压的主动让压支护体系和使围岩约束平稳过渡的措施可以推动应力拱圈形成,能承担高地应力环境下的压应力。

深井高应力软岩巷道底鼓力学机理及控制技术研究

为解决林西矿深井高应力软岩巷道底鼓问题,论文通过理论分析和现场实测相结合方法,研究分析出了深井高应力软岩巷道底鼓力学机理及控制技术,得出了如下结论:(1)推导出了巷道两侧底板极限破坏深度、极限破坏宽度以及沿滑移面有效滑动力的计算公式;(2)判断出了林西矿1791-2工作面回风巷底板破坏为挤压流动性底鼓,全断面破坏鼓起形式;(3)分析出了巷道底鼓机理、底鼓原因以及控制途径;(4)提出了“顶、帮、底同治”控制巷道底鼓技术,顶帮采用高强预应力锚杆网+锚索支护,底板采用预应力锚索锚注加固+混凝土铺底技术;(5)现场工业试验表明巷道底鼓得到了有效遏止,能够满足正常使用要求。

软岩大变形铁路隧道控变技术措施

结合具体工程实例,介绍了高地应力作用下的软岩隧道挤压变形概念,通过对隧道高地应力软岩大变形情况的研究,提出了隧道工程变形控制技术措施。经过实践得出结论,论文提出的技术措施可以控制铁路隧道高地应力软岩大变形问题,确保隧道工程施工质量,为工程顺利进行提供了保障。

深部软岩巷道变形破坏原因及支护技术研究

为了解决深部破碎软岩巷道围岩大变形、难支护的问题,以山西宁武德盛煤业有限公司502采区轨道大巷为工程背景,通过现场勘测和试验研究分析了巷道围岩变形破坏机理,得出围岩强度低、易软化是围岩大变形的内在原因,而高地应力则是大变形的外在诱因。据此提出了“锚杆+锚索+钢筋网+喷射混凝土+注浆”联合支护技术方案,并通过数值计算验证了该方案的可靠性。现场监测结果表明,采用该联合支护技术方案后,巷道顶板最大下沉量为73.1 mm,两帮最大移近量为153.9 mm,最大底鼓量为88.7 mm,围岩变形量均在规定允许值以内,且监测结果与数值计算结果相吻合,有效控制了深部破碎软岩巷道围岩的变形破坏。

高地应力软岩隧道围岩大变形控制关键技术研究

高地应力软弱围岩隧道施工易发生软岩大变形不良地质灾害,进一步引发掌子面失稳塌方、初支结构破坏、钢拱架弯折、初支结构侵限等不良现象,严重影响施工安全,阻碍工期。依托九绵高速白马隧道工程,采用现场监测的研究手段,从围岩特性、施工工法、循环步距等方面系统分析白马隧道产生大变形的根本原因,并从围岩变形机理出发,提出了一套综合施工工法、支护措施等方面的软岩大变形防治方案,解决了高地应力软岩大变形隧道初期支护受围岩应力挤压收敛变形的难题,实现了隧道初期支护无开裂、扭曲、折断、侵限的目的,可为类似工程提供一定参考。