Design of the yielding support used highly deformable elements for a tunnel excavated in squeezing rock

Yielding support is often used in the squeezing tunnel to prevent damage to the lining induced by large deformation of the surrounding rock.Highly Deformable Elements(HDE)which is often installed along the circumferential direction of the shotcrete lining is a common type of yielding support.To determine the yield parameters of HDE,the support characteristic of the lining using HDE and the ground pressure considering strain-softening of soft rock were analyzed by an analytical method.The analytical solution showed that when considering the strain-softening of squeezing ground,the ground pressure has a non-zero minimum value.The minimum value of ground stress can be used to determine the constant yield stress of the HDE,and the corresponding deformation of the minimum ground pressure can be used to determine the deformation capacity of the HDE.Based on the variation in the design constant yield stress and yield displacement of HDE with the in-situ stress and the mechanical parameters of the soft rock,equations were proposed for determining of the yield parameters of the HDE.

Support failure of a high-stress soft-rock roadway in deep coal mine and the equalized yielding support technology： a case study

Abstract There are many soft-rock roadway coal mines in China. The surrounding rocks of the high-stress soft-rock roadways in deep mine are especially difficult to be supported using the traditional supporting way. In this study, the south wing rail roadway on the second level of Yunjialing coal mine in China was used as an example to analyze the deformation and failure characteristics and influencing factors of roadway. On this basis, this study proposed the equalized yielding support idea which employs the yielding rings to realize the pressure equalization on the bolts and cables in the section. To achieve this purpose, the first bolt-mesh-cable equalizing pressure yielding support was integrated with the second grouting reinforcement. The results proved that the yield rings of the bolts and cables on the spandrel of the arched roadway firstly developed yielding deformation; then the deformation extended to the vault of the roadway; the bolts and cables achieved a yielding extreme value of 15 and 18 tonnes, respectively. The roadway surrounding rock tended to be stable at the 26th day after the maintenance. The equalizing pressure yielding supporting technology plays a moderate pressure-releasing and actively controlling role on the surrounding rocks in the soft-rock roadway with large deformation.

A critical review on the developments of rock support systems in high stress ground conditions

Extreme ground behaviour in high-stress rock masses such as rockburst prone and squeezing ground conditions are encountered in a range of underground projects both in civil and mining applications.The occurrence of such ground behaviour types are difficult to predict and special design and construction measures must be taken to control them.Determining the most appropriate support system in such grounds is one of the major challenges for ground control engineers because there are many contributing factors to be considered,such as the rock mass parameters,the stress condition,the type and performance of the support systems,the condition of major geological structures and the size and geometry of the underground excavation.The main characteristics and support requirements of rockburst-prone and squeezing ground conditions are herein critically reviewed and characteristics of support functions are discussed.Different types of energy-absorbing rockbolts and other support elements applicable for ground support in burst-prone and squeezing grounds are introduced.Important differences in the choice and economics of ground support strategies in high-stress ground conditions between civil tunnels and mining excavations are discussed.Ground support benchmarking data and mitigation measures for mines and civil tunnels in burst-prone,squeezing and heavily swelling grounds conditions are briefly presented by some examples in practice.

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.

Unified semi-analytical solution for elastic-plastic stress of deep circular hydraulic tunnel with support yielding

A unified semi-analytical solution is presented for elastic-plastic stress of a deep circular hydraulic tunnel with support yielding under plane strain conditions.The rock mass is assumed to be elastic-perfectly plastic and governed by the unified strength theory (UST).Different major principal stresses in different engineering situations and different support yielding conditions are both considered.The unified solution obtained in this work is a series of results,rather than one specific solution,hence it is suitable for a wide range of rock masses.In addition,parametric study is conducted to investigate the effect of intermediate principal stress.The result shows the major principal stress should be rationally chosen according to different engineering conditions.Finally,the applicability of the unified solution is discussed according to the critical pressures.

High-resistance controlled yielding supporting technique in deep-well oil shale roadways

In order to avoid the deep-well oil shale roadway being deformed, damaged, or difficult to maintain after excavating and supporting in Haishiwan coal mine, this paper has analyzed the characteristics of the deformed roadway and revealed its failure mechanism by taking comprehensively the methods of field geological investigation, displacement monitoring of surrounding rock, rock properties and hydration properties experiments and field application tests. Based on this work, the high-resistance controlled yielding supporting principle is proposed, which is： to ＂resist＂ by high pre-tightening force and high stiff- ness in the early stage, to ＂yield＂ by making use of the controlled deformation of a yielding tube in the middle stage, and to ＂fix＂ by applying total-section Gunite in the later stage. A high-resistance controlled yielding supporting technique of ＂high pre-tightening force yielding anchor bolt ＋ small-bore pre-tight- ening force anchor cable ＋ rebar ladder beam ＋ rhombic metal mesh ＋ lagging gunite＂ has been estab- lished, and industrial on site testing implemented. The practical results show that the high-resistance controlled yielding supporting technique can effectively control the large deformation and long-time rheology of deep-well oil shale roadways and can provide beneficial references for the maintenance of other con-generic roadways.Deep-well Oil shale

Experimental study on performance of spring damping support structure system for large deformation tunnel in soft rock

According to the convergence confinement theory,it is an effective measure to control the large deformation of high ground stress in fractured soft rock tunnels by using yielding support.The yielding support can be classified as either radial or circumferential yielding support.Circumferential yielding support is achieved by transforming radial displacement into circumferential tangential closure without compromising the support capacity of the primary lining support structure.Based on this,and inspired by the design principle of dampers,a yielding support structure system with spring damping elements as its core was developed,based on the connection characteristics of steel arches in highway tunnel,which can provide increasing support resistance in the yielding deformation section.Then the mechanical properties of spring damping elements were obtained through indoor axial pressure and flexural tests.In addition,according to these results with numerical calculations,the yielding support structure system with embedded spring damping elements can reduce the internal force of the support structure by approximately 10%and increase the area of the plastic zone of the surrounding rock by 11.23%,which can fully utilize the self-bearing capacity of surrounding rock and verify the effectiveness of circumferential yielding support.Finally,the spring damping support structure system was designed with reference to the construction process of the tunnel excavated by drilling and blasting method,and the transformation of the spring damping element to spring damping support structure was achieved.Based on field test results,surrounding ground pressure for the yielding support optimization scheme was reduced by 40%and more evenly distributed,resulting in the successful application and a reduction in the construction cost of large deformation tunnels in soft rock.

让压支护技术在软岩大变形隧道中的应用探讨

以新型让压锚杆的研发及其在煤矿系统大变形巷道中的成功应用为基础,提出了在交通隧道软岩大变形支护过程中应采用"及时支护、强支护与让压支护"三者相结合的基本原则,即保持一定支护阻力维持围岩稳定的同时,允许支护体系产生一定的位移,以达到支护、让压及卸载多重并举的功能。并据此设计了由让压锚杆、喷射砼、让压控制器及钢拱架等组成的让压支护体系。通过探讨让压锚杆的基本作用机理,对让压支护系统的各组成构件、关键技术等问题深入分析,提出了让压支护系统中构件间的组合方式,指出了今后需解决的关键技术问题:即保持让压支护系统变形协调性及稳定性,确定围岩自由变形量、围岩-支护共同变形量及恒阻让压量三者之间的关系,科学设定起始让压荷载及保持构件恒阻让压特性等。同时建议未来依托合适的工程背景开展让压支护系统的现场试验研究,进一步验证该系统的可靠性与适宜性。

大变形锚杆-围岩耦合模型及其计算方法

在矿山、水利、交通等工程领域中大变形锚杆已经获得了广泛的认可和应用,而相应理论水平落后于工程实践的现状则限制了大变形锚杆支护技术的进一步发展。针对大变形锚杆的力学及变形特性,提出了一种锚杆-围岩耦合作用结构模型,并基于塑性增量理论,从锚杆-围岩相互作用的角度,提出了大变形锚杆加固岩体的求解方法,推导了加锚岩体的平衡方程、位移协调方程和锚杆响应方程。在Visual Basic开发环境中编制有限差分计算程序,利用龙格库塔法求得了大变形锚杆-围岩耦合模型的半解析解,并通过数值模拟验证了理论模型的有效性。基于上述理论模型和计算方法,不仅可以计算得到大变形锚杆轴力和剪应力分布情况,定量分析其支护效应,还可以系统地求得加锚岩体的地层响应曲线及锚杆自身的响应曲线,对于地下工程中大变形锚杆的支护设计有基础性指导意义。

黄河多沙粗沙区分布式土壤流失模型支持系统

利用3S技术,以黄河多沙粗沙区小流域分布式土壤流失数学模型为服务对象,建立模型支持系统。所建支持系统具有数据管理灵活高效、系统适用面广、易于扩充,以及可以实现各类数据实时生成的优点;达到了流域地形和水沙演进数据的自动提取;提出了虚拟现实环境参照下分类模板定义的方法,提高了遥感影像的分类精度,有效地解决了辨别"同物异谱、异物同谱"现象的问题;实现了GIS功能与专业模型的紧密耦合,两者之间的信息可以进行双向交换和修改。

精准农业的研究应用现状和发展趋势(综述)

精准农业是基于信息和知识支持的集成技术管理的现代化农业。它是高效利用农业资源、减少环境污染、保持农业可持续发展的系统工程。本文简要介绍了支持精准农业系统的主要关键技术、研究应用现状和发展趋势。

综合气候条件的变量施肥决策支持系统研究

实施精准农业是促进农业可持续发展的有效途径,而变量施肥是精准农业的核心。介绍了一种基于养分平衡法的变量施肥决策支持系统的功能及其组成,并将气候条件考虑到参数的确定中,初次利用气候条件确定其中一个参数—"目标产量",从而使施肥量更加合理。系统综合考虑了气候条件对目标产量的影响,比传统的以地定产法更贴近实际;以ASP.NET为网络开发技术、VisuaStudio.Net为编程环境、VC++6.0为编程语言,使用Microsoft SQL Server开发数据库,并利用GIS相关软件进行专题图制作。与其他系统相比,此系统具有操作简单、成本低的特点。

高应力软岩巷道可接长锚杆让压支护技术

高应力软岩巷道的塑性区范围和变形量均较大,其稳定型控制需要支护材料具备良好的延伸性能及深部锚固特性。基于'高阻让压'而研发的可接长锚杆长度大于4 m、延伸率为17%,破断载荷为195 kN,能够适应此类巷道的变形破坏特征。根据支护材料和围岩的变形破坏特征,分别建立了可接长锚杆和'锚杆+锚索'支护系统的本构模型,结果表明:为保证支护结构稳定,避免支护系统本构模型失稳后应变量剧增,支护系统本构模型的应变上限不能超过支护元件的最大应变量;可接长锚杆能够能提供远大于锚索的让压距离,保障软岩巷道支护系统的支护强度和稳定性。试验条件下,可接长锚杆的平均支护阻力约为170.2 kN,顶板0~4 m内围岩理论变形量为264 mm,与工程实际变形量比较接近,起到了对高应力软岩巷道顶板的让压支护的目标。

基于网格的速丰林决策支持系统构建

基于专家决策系统与网络技术、网格技术以及Web--GIS技术发展现状,运用系统工程学方法,力求构建一个立体的开放式速丰林经营培育决策支持平台,即能够支持不同树种、不同地域与不同立地条件下的决策支持平台。在这个系统内,综合运用XML、Web服务(Web Services)、数据网格(Data Grid)等信息技术,遵循信息集成技术和森林资源管理的最新发展趋势,以相关树种知识信息、空间信息和属性信息为主线,通过各种信息相互关联、作用和分析,为林分经营提供一个更加广泛、更加形象化的决策支持环境及其支撑工具,构造并提高各种经营方案的实时性、准确性、数量化和最优化程度。该系统不仅为林业基础生产单元,如林场、林局和广大林农提供信息服务,同时,随着系统基础数据、知识库、模型库及相关服务的扩充,也可以为决策部门和科研部门提供决策支持和研究支持。

加工番茄产量组合预测模型研究

为了实现加工番茄产量的精准预测,通过采用方差倒数法来确定权重,将一元线性回归模型、灰色预测模型和指数平滑模型加以组合,根据2001—2009年新疆某加工番茄种植及产量数据,建立了加工番茄产量组合预测模型。以预测2010年和2011年番茄产量为例,结果表明此组合预测模型与单一预测模型相比更加准确可靠。该研究为加工番茄产业决策支持系统的建立奠定了理论基础。

高速公路小净距隧道合理净距的探讨

结合京福高速公路三明—福州段小净距隧道工程实践 ,对II类围岩在相同埋深(H =30 .0m)、相同支护措施、不同净距 (L =3.0m～ 8.0m)条件下 ,隧道围岩 -支护结构体的屈服接近度、隧道周边典型位置的位移及中夹岩位移进行了数值模拟研究。数值分析结果表明 :当采用侧壁导坑法施工时 ,隧道中夹岩的优化合理净距为L =8.0m ,如对中夹岩下部左、右脚进行加强支护 ,L =6.0m也是较合理的 ;当采用台阶 -侧壁导坑组合法施工时 ,中夹岩合理净距也应取L =8.0m ,如对中夹岩上、下部进行加强支护 ,取L =7.0m和 6.

构造复杂区巷道让均压锚网索非均称支护技术试验

针对宝积山煤矿707工作面构造复杂区巷道非对称变形破坏与支护结构失效严重的现象,对其破坏机理进行理论分析与数值模拟。结果表明:非对称应力场、关键部位的拉剪混合破坏、应力集中是巷道变形破坏的主要原因,并提出让均压锚网索非均称支护技术。现场实践表明,采用高强高预应力锚杆、非均称支护、让均压支护方案后,巷道变形量与非对称性得到有效控制,120 d内巷道顶底板移近量138 mm,两帮移近量98 mm,巷道围岩稳定性大幅提高。

高应力软岩巷道高强让压锚杆支护系统试验研究

为解决云驾岭煤矿二水平南翼下山巷道掘进过程中出现的围岩变形大,且返修后仍不能有效控制巷道稳定的支护问题,采用高强高预紧力让压锚杆支护系统在二水平南翼运输下山巷道进行了支护试验。试验巷道选用Q600高强让压锚杆和直径18.9 mm的"鸟窝"让压锚索,设计预紧力分别为80和150 kN。监测结果表明:试验巷道顶板下沉量最大值46 mm,两帮移近量最大值182 mm,基本无底鼓现象,通过安装高强度、高预紧力让压锚杆高强支护系统能适应高应力软岩巷道的支护要求,实现了高应力软岩运输下山的一次支护成功。

Stability control of surrounding rocks for a coal roadway in a deep tectonic region

In order to effectively control the deformation and failure of surrounding rocks in a coal roadway in a deep tectonic region, the deformation and failure mechanism and stability control mechanism were studied. With such methods as numerical simulation and field testing, the distribution law of the displacement, stress and plastic zone in the surrounding rocks was analyzed. The deformation and failure mechanisms of coal roadways in deep tectonic areas were revealed: under high tectonic stress, two sides will slide along the roof or floor; while the plastic zone of the two sides will extend along the roof or floor,leading to more serious deformation and failure in the corner of two sides and the bolt supporting the corners is readily cut off by the shear force or tension force. Aimed at controlling the large slippage deformation of the two sides, serious deformation and failure in the corners of the two sides and massive bolt breakage, a ‘‘controlling and yielding coupling support'' control technology is proposed. Firstly, bolts which do not pass through the bedding plane should be used in the corners of the roadway, allowing the two sides to have some degree of sliding to achieve the purpose of ‘‘yielding'' support, and which avoid breakage of the bolts in the corner. After yielding support, bolts in the corner of the roadway and which pass through the bedding plane should be used to control the deformation and failure of the coal in the corner. ‘‘Controlling and yielding coupling support'' technology has been successfully applied in engineering practice, and the stability of deep coal roadway has been greatly improved.

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.