Deformation mechanism and collapse treatment of the rock surrounding a shallow tunnel based on on-site monitoring

When tunnels are constructed at shallow depths in areas with poor geological conditions,such as portal sections,valleys and hillsides in regions with granitic bedrock,considerable excavation-induced deformation of the surrounding rock may occur,potentially resulting in tunnel collapses.The main reason for these problems is the lack of understanding of the deformation mechanism and evolution of the soft granitic rock surrounding the tunnel and the adoption of inappropriate construction technology and methods.This article analyzes the deformation mechanism of the rock surrounding a shallow tunnel based on in situ monitoring data as a case study and suggests that certain measures should be taken to effectively control the deformation of the surrounding rock and to minimize the potential for tunnel collapse.The results show that the deformation of the granitic soil surrounding the tunnel can be divided into three stages:the rapid deformation stage,the slow deformation stage and the stabilization stage.Appropriate construction methods should be carefully selected to ensure safety during tunnel excavation in the first stage.To avoid secondary disasters caused by tunnel collapses,three treatment measures may be implemented as part of safety management:enhancing the monitoring of the surrounding rock deformation,adjusting the construction methods and optimizing the support systems.In particular,accurate monitoring data and timely information feedback play a vital role in tunnel construction.Therefore,engineers with considerable engineering experience and professional knowledge are needed to analyze the monitoring data and make accurate predictions of tunnel deformation to ensure that reasonable measures are taken in the process of shallow tunnel excavation.

Study on creep deformation and energy development of underground surrounding rock under four‐dimensional support

There is an urgent need to develop optimal solutions for deformation control of deep high‐stress roadways,one of the critical problems in underground engineering.The previously proposed four‐dimensional support(hereinafter 4D support),as a new support technology,can set the roadway surrounding rock under three‐dimensional pressure in the new balanced structure,and prevent instability of surrounding rock in underground engineering.However,the influence of roadway depth and creep deformation on the surrounding rock supported by 4D support is still unknown.This study investigated the influence of roadway depth and creep deformation time on the instability of surrounding rock by analyzing the energy development.The elastic strain energy was analyzed using the program redeveloped in FLAC3D.The numerical simulation results indicate that the combined support mode of 4D roof supports and conventional side supports is highly applicable to the stability control of surrounding rock with a roadway depth exceeding 520 m.With the increase of roadway depth,4D support can effectively restrain the area and depth of plastic deformation in the surrounding rock.Further,4D support limits the accumulation range and rate of elastic strain energy as the creep deformation time increases.4D support can effectively reduce the plastic deformation of roadway surrounding rock and maintain the stability for a long deformation period of 6 months.As confirmed by in situ monitoring results,4D support is more effective for the long‐term stability control of surrounding rock than conventional support.

THE RELATION BETWEEN THE CHAIN PILLAR WIDTH AND THE SURROUNDING ROCK DEFORMATION OF ROADWAY

Based on the analysis and research into ground pressure behavior law and surrounding rock deformation of a large number of roadways affected by mining activity,this paper proposed a relation between the surrounding rock deformation during mining ,the surrounding rock deformation rate during stable stage of mining and the chain pillar width. Moreover,it established the relation between the total amount of surrounding rock deformation during service period of roadway and the chain pillar width,which provides a principal basis for choosing the chain pillar width.

Numerical analysis of deformation and failure characteristics of deep roadway surrounding rock under static-dynamic coupling stress

In actual production,deep coal mine roadways are often under typical static-dynamic coupling stress(SDCS)conditions with high ground stress and strong dynamic disturbances.With the increasing number of disasters and accidents induced by SDCS conditions,the safe and efficient production of coal mines is seriously threatened.Therefore,it is of great practical significance to study the deformation and failure characteristics of the roadway surrounding rock under SDCS.In this paper,the effects of different in-situ stress fields and dynamic load conditions on the surrounding rock are studied by numerical simulations,and the deformation and failure characteristics are obtained.According to the simulation results,the horizontal stress,vertical stress and dynamic disturbance have a positive correlation with the plastic failure of the surrounding rock.Among these factors,the influence of the dynamic disturbance is the most substantial.Under the same stress conditions,the extents of deformation and plastic failure of the roof and ribs are always greater than those of the floor.The effect of horizontal stresses on the roadway deformation is more notable than that of vertical stresses.The results indicate that for the roadway under high-stress conditions,the in-situ stress test must be strengthened first.After determining the magnitude of the in-situ stress,the location of the roadway should be reasonably arranged in the design to optimize the mining sequence.For roadways that are strongly disturbed by dynamic loads,rock supports(rebar/cable bolts,steel set etc.)that are capable of maintaining their effectiveness without failure after certain dynamic loads are required.The results of this study contribute to understanding the characteristics of the roadway deformation and failure under SDCS,and can be used to provide a basis for the support design and optimization under similar geological and geotechnical circumstances.

Deformation characteristics of surrounding rock of broken and soft rock roadway

A similar material model and a numerical simulation were constructed and are described herein. The deformation and failure of surrounding rock of broken and soft roadway are studied by using these models. The deformation of the roof and floor, the relative deformation of the two sides and the deformation of the deep surrounding rock are predicted using the model. Measurements in a working mine are compared to the results of the models. The results show that the surrounding rock shows clear theological features under high stress conditions. Deformation is unequally distributed across the whole section. The surrounding rock exhibited three deformation stages： displacement caused by stress concentration, theological displacement after the digging effects had stabilized and displacement caused by supporting pressure of the roadway. Floor heave was serious, accounting for 65% of the total deformation of the roof and floor. Floor heave is the main reason for failure of the surrounding rock. The reasons for deformation of the surrounding rock are discussed based on the similar material and numerical simulations.

Deformation mechanism of high-stress and broken-expansion surrounding rock and supporting optimization based on the gray correlation theory

Aiming at the large deformation and support problems of high-stress and broken-expansion surrounding rock, and taking 1 000 m level roadway of Mine II in Jinchuan as the research object, an investigation on the deformation and damage of roadway surrounding rock and an analysis of its mechanism were carried out. The gray correlation theory was used in support scheme optimization design. First, causes and mechanism of deformation of the 1 000 m horizontal transport channel were analyzed through field investigation, laboratory test and data processing methods. We arguued that poor engineering geological conditions and deep pressure increases were the main factors, and the deformation mechanism was mainly the ground deformation pressure. Second, the gray correlation theory was used to construct supporting optimization decision method in the deep roadway. This method more comprehensively considers various factors, including construction, costs, and supporting material functions. The combined support with pre-stressed anchor cables, shotcrete layer, bolt and metal net was put forward according to the actual roadway engineering characteristics. Finally, 4 support schemes were put forward for new roadways. The gray relational theory was applied to optimizing the supporting method, undertaking technical and economic comparison to obtain the correlation degree, and accordingly the schemes were evaluated. It was concluded as follows： the best was the flexible retaining scheme using the steel strand anchor; the second best was the one using plate anchors on the top and rigid common screw steel bolt on the two sides; the ttiird was; the rigid common screw steel bolt in full section of roadway; and the worst is the planished steel rigid support. The optimized scheme was applied to the 1000 m level of new excavation roadway. The results show that the roadway surrounding rock can reach a stable state after 5 to 6 months monitoring, with a convergence rate less than 1 mm/d.

Mechanism of rock deformation and failure and monitoring analysis in water-rich soft rock roadway of western China

Aiming to get the strata behavior and stability rules of surrounding rock of the main return airway of Yushujing Coal Mine, convergence deformation of two sides and force of U-shaped steel yieldable support and bolt were monitored, and deformation of surrounding rock and mechanical characteristics of support structure were timely obtained to guide the informa- tion construction and optimize supporting parameters in water-rich soft rock roadway. The field monitoring results indicate the following. （1） Convergence displacement of rock surface increases with time continuity and shows surrounding rock＇s intense theological behavior. The original support scheme cannot control the large deformation and strongly theological behavior; （2） Without backfilling, the U-shaped steel support begins to bear load after erecting for 4-7 days and increases rapidly in the first 30 days. The U-shaped steel support at the right shoulder and top of roadway bears a larger force and the left side and shoulder bears a smaller force; （3） The stress of bolt increasing over time and at the right shoulder of roadway has larger growth and value. The mechanism of rock deformation and the failure and strata behavior in water-rich soft rock roadway are revealed based on the results of the measured relaxation zone of surrounding rock, measured stresses, and the rock mechanics tests.

Non-contact monitoring and analysis system for tunnel surrounding rock deformation of underground engineering

It is very important to monitor surrounding rock deformation in tunnel construction. The principle, function, development and application of the system composed of a total station and computer for monitoring and analyzing surrounding rock deformation were discussed. The new methods of two free station of 3D measurement and its mathematic adjustment mode were presented. The development of software for total station on-board and post for computer were also described. Without centering it and measuring its height, the total station controlled by the software on-board can fulfill the whole measurements to target points. Monitoring data can be processed by the post software and results of regression analysis, forecasting information of the tunnel surrounding rock deformation can be provided in time. The practical use shows that this system is practicable, highly accurate and efficient. It satisfies the needs of safety and information construction in tunnel construction of underground engineering.

THE THEORY OF SUPPORTING BROKEN ZONE IN SURROUNDING ROCK

The first topic discussed in this paper is to evaluate the present supporting theories,among which the typical two are collapse arch and elasto-plastic theories. The former is rather limited in practical application,and the latter is built up on some assumptions which is inconsis-tent with the reality,for it is of no need to support a roadway of which the surrounding rock is in elasto-plastic state. The second topic is to prove the objective existence of the broken zone in surrounding rock(BZSR) by a series of laboratory experiments and field measurements. The paper indicates that the object to be supported mainly is the bulking or expanding force resulted from the development of BZSR. This is remarkably different from the existing points of view which have been generally recognized nowadays. So far ,this theory has been tested in supporting more than ten thousand meters roadways located in various strata and has proved itself to have a great technoeconomical benefit.

Deformation and failure of stratified weak roof strata of longwall roadway

A comprehensive underground monitoring was conducted in a coal mine. The purpose of this research was to clarify the deformation and failure behavior of stratified weak roof strata of longwall roadway in adverse ground conditions. The field investigation incorporating a range of geotechnical instrumentation was conducted over a period of time ever since the formation of opening the site was buried into the goaf of a retreating longwall panel. The roof layer deformation and failure characteristics associated with the three stages of heading development, after development and before extraction, as well as after longwall extraction were identified on the basis of field investigation and analytical study, the results clearly demonstrated that how the roof deformation and failure progress were strongly related to these three stages of the mining activities mentioned.

SELECTION OF HORIZONTAL DISTANCE X BETWEEN ROADWAY AND THE EDGE OF ITS UPPER PILLAR

The horizontal distance X between roadway and the edge of its upper pillar is considered as an important parameter for layout of roadway in floor strata or in the adjacent coal seam. Based on the research achievements of rockstrata pressure, this paper illustrates the quantitative relationship among the mining situation of upper searn, the rockstrata properties around roadway, the vertital distanee Z (between roadway and its upper pillar), and the horizontai distance X (between roadway and the edge of its upper pillar), and provides a main basiS for the selection of value X and the relative location between roadway and its upper seam.

厚煤层采准巷道布置及围岩稳定性研究

为了解厚煤层采准巷道布置形式对围岩稳定性的影响,文章通过数值模拟,分析了巷道沿顶掘进、布置在煤层中间和沿底掘进三种不同布置形式下围岩的变形情况,并监测巷道围岩的变形数据。研究发现,巷道沿底掘进时,整体变形较为均匀,顶板、帮部和底板位移梯度均较小,有利于增强围岩的稳定性。

三元石窟煤矿顶板淋水区域注浆封堵与锚索支护技术

传统支护技术在三元石窟煤业软岩淋水巷道中的应用效果不佳,采用注浆封堵与锚索支护工艺对巷道顶板支护技术进行改进。依托FLAC 3D数值模拟软件分析了1、5、10 MPa注浆压力与300、400、500 mm封孔长度条件下的锚索孔围岩变形量与封孔段围岩最大主应力的分布特征。在井下开展拉拔试验测试支护体力学性能,开展工业试验验证。结果表明:锚索孔围岩位移量随浆液压力的提升而增加。软弱粉砂岩条件下的注浆压力不宜大于5 MPa。封孔长度应以围岩的裂隙发育位置作为考量标准,当裂隙发育位置位于围岩深部区域时,封孔长度应相对较长,反之亦然。封孔长度的增加有利于提升锚索的抗拉强度。在现场实施注浆封堵与锚索支护工艺的50 d后,围岩变形基本达到稳定,且淋水现象大幅降低。

煤矿巷道掘进分次支护技术应用研究

文章针对煤矿巷道掘进过程中遇到的问题,特别是传统一次性支护导致掘进效率低等问题,引入分阶段支护理念,通过深入探究掘进过程中的时空效应,明确围岩变形与荷载释放之间的动态关系,进而得出分阶段支护方案。利用围岩自然稳定过程,分阶段施加必要的支护措施,既保证了巷道安全,又加速了掘进进程,并结合工程实践案例,充分验证了该技术的可行性,旨在为类似施工提供参考。

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。

高应力大巷底鼓机理及其稳定性控制方法

针对余吾煤业1号回风大巷在高应力扰动下出现的巷道底鼓严重问题,综合运用理论分析、数值计算和现场试验相结合的方法,系统研究了高应力大巷底鼓机理及其稳定性控制方法。理论计算结果表明,高应力巷道底板破坏深度达1.35 m,底板滑移面受到的滑动力达3.11 MPa,超过了底板砂质泥岩极限抗拉强度,导致巷道底板发生底鼓。从高应力巷道底鼓控制角度出发,提出了高应力巷道顶底板加强锚索与巷道两帮锚杆联合支护的巷道底鼓控制技术,数值模拟结果表明巷道底鼓量可降低67%,有效控制底鼓的同时,也可为巷道整体稳定提供支撑。通过现场试验,研究提出的巷道底鼓控制方法可使回风大巷顶板下沉值降低37%,底鼓值降低72%,两帮变形量降低53%,有效保证了回风大巷的稳定。研究结果对于指导深部矿井高应力环境下巷道底鼓控制具有重要实践意义。

动压巷道围岩变形机理及其控制技术研究

针对寺河煤矿二号井动压巷道在工作面回采过程中存在的围岩变形严重及工作面支架阻力过大等问题,采用现场监测与数值模拟相结合的手段,对动压巷道围岩变形机理及其控制技术进行了系统研究。结果表明,巷道在经受掘进支护及工作面的开采动压影响后,围岩应力水平升高,且两侧应力不平衡,帮部不对称变形严重,巷道围岩变形主要分为单侧采用影响与两侧采动影响2个阶段,巷道变形主要是因为采区大巷两侧工作面采动产生的应力扰动作用,导致巷道承载性能持续恶化,围岩发生反复变形破坏。据此,研究提出采用预裂切顶卸压技术对动压巷道变形实施有效控制,确定合理的切顶卸压高度与角度分别为16.5 m与60°。通过现场实践,对动压巷道实施切顶卸压后,围岩顶底板及两帮移近量较卸压前得到了有效控制,工作面支架阻力显著降低,保证了工作面动压巷道围岩的稳定。

高速公路隧道工程开挖方法比选分析

为了保证高速公路隧道在开挖期间的应力和变形在可控范围内,避免出现安全事故,以云湛高速公路的隧道为例,提出了四种开挖方法:台阶法、环形开挖留核心土法、交叉中隔墙法(CRD法)、单侧壁导坑法(CD法),基于“定性与定量相结合”的原则对隧道开挖方法进行对比。一方面,从施工安全性、复杂性、工期、造价、支护时效性等方面对隧道开挖方法定性比选,CD法开挖隧道安全性最好;另一方面,利用有限元软件建立计算模型,计算了隧道在不同开挖方法下的围岩应力和位移,发现隧道经CD法开挖后应力和位移最小。随后,利用全站仪对隧道CD法施工期间的拱顶沉降进行监测,监测时间超过60 d后,拱顶沉降基本稳定在20 mm,满足规范要求,说明CD法开挖隧道是可行的。

开拓矿淋水区巷道顶板围岩破坏规律及外注式锚注支护技术研究

受到顶板存在低层位弱含水层的影响,部分煤矿出现巷道顶板锚索孔长期淋水的现象,导致顶板泥质围岩软化、锚索支护结构失效,易诱发巷道顶板离层冒落等安全事故。文章以开拓矿11煤回风大巷淋水区为研究对象,通过围岩力学性能测试及钻孔窥视可知,顶板泥质岩围岩强度低、裂隙发育,容易遇水泥化。结合现场工程条件和锚注支护机理,提出了外注式锚注支护技术,并设计了淋水区巷道外注式锚注补强支护方案,通过数值分析、现场工业性试验和现场监测优化了补强支护参数和施工工艺,围岩离层变形量降低48%以上,顶板淋水量减少80%以上,确保了开拓煤矿煤巷淋水区顶板围岩稳定安全。

深部采矿岩石力学进展

随着煤炭开采日益向深部发展,深部采矿引发的围岩大变形破坏和强冲击动力灾害日益严峻。在深部高地应力、高地温、高渗透压、强采动、强流变及多场耦合的复杂地质力学环境下,深部采场的应力场特征、煤岩体破碎性质、岩层移动及能量的积聚释放规律等均发生了显著变化。针对深部采矿中的岩石力学问题,论述了笔者及团队在深部采煤方法、深部巷道破坏机理与围岩控制、深井热害与地热利用三大方向取得的进展,主要包括:(1)提出了平衡开采理论和实现平衡开采的110/N00工法,进行了千米深井现场工程应用;(2)构建了深部“非均压建井”模式,研发了实现深井稳定提升的SAP系统,形成了可大幅简化井巷工程量和提高矿井采出率的建井方法;(3)研发了多套适用于研究深部岩体在水、高温、高压、结构效应及多场耦合作用下发生宏观破坏的实验系统和可进行微观层面演算的超算系统,揭示了深部软岩大变形破坏机理及多尺度力学特性;(4)研制了深部岩体冲击型和应变型岩爆实验系统,阐述了深部岩体冲击能量沿开挖临空面瞬间释放的非线性动力学行为;(5)提出了深部巷道开挖补偿支护理论,进一步发展了具有高恒阻、高延伸率、强吸能和耐冲击超常力学特性的NPR支护材料和技术;(6)研发了模拟深部高温、高湿和高压环境下的岩体热力学实验系统,提出了热害治理和热能资源化利用方法,建立了深部热害治理与热能综合利用系统(HEMS)。相关研究成果已在深部开采领域得以应用,可为深部采矿面临的复杂岩石力学问题提供借鉴。