A 2D stability analysis of the rock surrounding underground liquified natural gas storage cavern based on COMSOL Multiphysics

Underground liquified natural gas(LNG)storage is essential in guaranteeing national energy strategic reserves,and its construction is being accelerated.The stability of surrounding rock of underground LNG storage caverns under stress-low temperature coupling effect is the key factor determining the feasibility of LNG storage.First,a mathematical model used for controlling the stress-low temperature coupling and the processes of rock damage evolution is given,followed by a 2-D numerical execution process of the mathematical model mentioned above described based on Comsol Multiphysics and Matlab code.Finally,a series of 2-D simulations are performed to study the influence of LNG storage cavern layout,burial depth,temperature and internal pressure on the stability of surrounding rocks of these underground storage caverns.The results indicate that all the factors mentioned above affect the evolution of deformation and plastic zone of surrounding rocks.The research results contribute to the engineering design of underground LNG storage caverns.

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.

Influence of underground water seepage flow on surrounding rock deformation of multi-arch tunnel

Based on a typical multi-arch tunnel in a freeway, the fast Lagrangian analysis of continua in 3 dimensions(FLAC3D) was used to calculate the surrounding rock deformation of the tunnel under which the effect of underground water seepage flow was taken into account or not. The distribution of displacement field around the multi-arch tunnel, which is influenced by the seepage field, was gained. The result indicates that the settlement values of the vault derived from coupling analysis are bigger when considering the seepage flow effect than that not considering. Through the contrast of arch subsidence quantities calculated by two kinds of computation situations, and the comparison between the calculated and measured value of tunnel vault settlement, it is found that the calculated value(5.7-6.0 mm) derived from considering the seepage effect is more close to the measured value(5.8-6.8 mm). Therefore, it is quite necessary to consider the seepage flow effect of the underground water in aquiferous stratum for multi-arch tunnel design.

Stability of coal pillar in gob-side entry driving under unstable overlying strata and its coupling support control technique

Considering the situation that it is difficult to control the stability of narrow coal pillar in gob-side entry driving under unstable overlying strata, the finite difference numerical simulation method was adopted to analyze the inner stress distribution and its evolution regularity, as well as the deformation characteristics of narrow coal pillar in gob-side entry driving, in the whole process from entry driving of last working face to the present working face mining. A new method of narrow coal pillar control based on the triune coupling support technique (TCST), which includes that high-strength prestressed thread steel bolt is used to strain the coal on the goaf side, and that short bolt to control the integrity of global displacement zone in coal pillar on the entry side, and that long grouting cable to fix anchor point to constrain the bed separation between global displacement zone and fixed zone, is thereby generated and applied to the field production. The result indicates that after entry excavating along the gob under unstable overlying strata, the supporting structure left on the gob side of narrow coal pillar is basically invalid to maintain the coal-pillar stability, and the large deformation of the pillar on the gob side is evident. Except for the significant dynamic pressure appearing in the coal mining of last working face and overlying strata stabilizing process, the stress variation inside the coal pillar in other stages are rather steady, however, the stress expansion is obvious and the coal pillar continues to deform. Once the gob-side entry driving is completed, a global displacement zone on the entry side appears in the shallow part of the pillar, whereas, a relatively steady fixed zone staying almost still in gob-side entry driving and present working face mining is found in the deep part of the pillar. The application of TCST can not only avoid the failure of pillar supporting structure, but exert the supporting capacity of the bolting structure left in the pillar of last sublevel entry, thus to jointly maintain the stability of coal pillar.

降雨入渗对防军隧道浅埋小净距段围岩稳定性的影响

为控制降雨入渗对浅埋小净距隧道围岩稳定性的影响,以义东高速公路防军隧道为依托,基于流固耦合理论和水土特征曲线,采用MIDAS GTS NX有限元软件建立浅埋小净距隧道数值模型,对雨季施工时的土体孔隙水压力、围岩变形特征和边仰坡安全系数展开分析。结果表明:随着降雨入渗的持续,围岩及边仰坡土体基质吸力逐渐减小,其土体抗剪强度也随之降低,稳定性变差。经过7 d累积降雨,孔隙水压力增大趋势逐渐放缓,围岩变形达到最大值,工况1的拱顶沉降增大了21.48%,且边仰坡安全系数小于1,处于失稳状态。洞口段采取加固和排水措施来控制围岩的稳定性,边仰坡的安全系数较加固前提升了17.27%,取得了良好的效果,保证了隧道后期的安全施工。

6~10 m厚煤层超大采高液压支架及其工作面系统自适应智能耦合控制

厚煤层储量及产量占我国原煤总储量及产量的一半,通过梳理厚煤层开采历史沿革,总结了我国厚煤层开采40年来的技术及装备研发实践,系统分析了以高端大采高液压支架及围岩智能耦合理论为代表的6~10 m大采高综采高效智能化综采技术及装备研究进展,提出了大采高支护理论及围岩智能耦合控制的突破是厚煤层一次开采高度突破的首要因素,完善的感知体系建立是液压支架自适应支护的前提,数字技术的应用为大采高工作面高效推进及装备智能协同控制提供了新的技术途径;阐明了大采高综放液压支架与围岩耦合关系,剖析了采高增加对硬煤层冒放性的有利影响,提出了基于煤矸识别、放煤机构控制的“纯煤段记忆放煤+煤岩分界模糊段人工反馈式干预放煤”的智能放煤控制策略;分析了大采高开采“采–运”协同智能耦合控制关键技术,构建了基于采煤机牵引速度与刮板输送机链速间联动调节的工作面装备间多机异构耦合自适应协同控制模型;研发了厚煤层开采中10 m超大采高液压支架,分析了厚煤层开采不断突破开采高度极限的新认识,从开采装备、控制系统等方面提出厚煤层一次开采高度的突破的研发方向。

掩护式液压支架四连杆承载特性响应分析

四连杆作为液压支架的支撑部件,在冲击载荷下易发生失稳导致破坏。基于顶梁的承载特性,通过分析液压支架与围岩在不同情况下的耦合状态,进一步研究了液压支架四连杆的力学响应特性。基于Denavit-Hartenberg(D-H)理论,利用MATLAB软件,建立液压支架全姿态的动力学模型,分析液压支架的平衡缸和立柱的不同铰接位置对四连杆负载的影响。结果表明:立柱和平衡杠的安装位置越靠近顶梁前端,支架四连杆的负载越大,其对应的负载最大值也越大;前连杆最大值发生位置逐渐向煤壁方向移动,而后连杆则向采空区移动;立柱和平衡缸安装位置的前移增大了四连杆的负载,因此,合理的支架结构设计能在一定程度上优化支架的负载。

破碎软弱围岩巷道耦合支护技术研究

受开采扰动破碎围岩巷道容易发生变形破坏,是矿山深部开采面临的重要支护难题。以昆阳磷矿二矿破碎、极破碎地段巷道破坏为研究背景,采用有限元分析方法分析巷道开挖后围岩位移、应力分布特征、塑性区范围。研究发现巷道开挖后两帮出现拉伸破坏,拱肩部位产生大量的剪切塑性区,顶板区域发生贯通的变形破坏机理。因此,提出采用钢拱架、锁脚锚杆、钢筋网、连接筋、喷混凝土耦合支护形式防止巷道坍塌。通过现场应用表明:采用此耦合支护技术可有效控制破碎软弱巷道围岩的变形,支护效果良好。研究结果为类似工程地质条件下的巷道支护提供了借鉴。

水力耦合作用下煤变形及渗透率响应规律研究

煤层注水过程中,应力与水压产生耦合作用使煤体形变,影响煤岩渗流。为探究注水渗流过程中煤岩体积应变和渗透特性演化规律,利用岩石力学试验机,对煤岩开展水力耦合渗流试验,得出应力对煤岩渗透率和体积应变特征的影响规律,从而探究水压影响下煤岩体积应变和渗透特性演化规律。试验结果表明:渗透率对于体积应变存在着明显的响应规律,通过数据拟合得到煤岩渗透率和体积应变存在指数函数关系;恒定水压试验中,煤岩渗透率呈现先减后增的趋势,此过程试件经历了由压缩到扩展的过程,在煤岩裂隙贯通后渗透率达到极大值;变水压试验过程中,煤岩裂隙在较少的水压循环次数下处于压密状态,渗透率波动下降,但随循环次数增加,裂隙扩张,煤岩渗透率在水力耦合作用下开始增加;相同应力条件下,高孔隙水压促进裂隙扩展,促进体积应变量的增加以及渗透率的增长。

基于大型隧道围岩相似材料的配制方法研究

【目的】通过分析国内研究成果调研公路隧道大型模型试验的相似材料配比,针对大型隧道围岩相似材料的配制方法展开研究。研究出一种由重晶石粉、石英砂、白水泥、铁粉、硅油和水组成的液固耦合相似材料。【方法】通过室内实验探究不同配比对材料各种物理性质和水理性的影响,并且确定了液固耦合相似材料的具体配比结果。【结果】实验结果表明,在材料成分含量不变的情况下,白水泥的含量增加会大幅度降低材料的渗透系数,胶结剂会明显地影响材料的弹性模量和抗压强度。此外,随着材料中重晶石粉与白水泥的比例逐渐增加,试验材料的抗压强度会逐渐提高,但是当材料中重晶石粉与白水泥的含量达到一定含量时,材料的抗压强度可能略微降低。在一定范围内增加重晶石粉与白水泥的比例可以提高材料的弹性模量。抗剪强度受硅油影响明显。【结论】液固耦合相似材料能够模拟不同强度具有不同渗透性的岩体材料,是一种理想的相似模拟材料。

耦合让均压支护在深部开采矿井软岩支护中的应用

深部软岩巷道围岩控制面临围岩变形量大、支护体受力大以及围岩控制困难等问题,是矿井深部开采期间需解决的现实问题。以11306运输巷围岩支护为工程背景,针对巷道埋深大(平均埋深680 m)、围岩松软(顶底板为砂质泥岩、泥岩)问题,在分析原有锚网索支护体系失效原因基础上,提出将耦合让均压支护应用到巷道围岩控制中。耦合让均压支护中使用的让压蛇形锚杆、让压鸟窝恒阻锚索及“JW”钢带、柔性纤维网等均具有抗变形能力强、支护强度大优点,同时让压蛇形锚杆、让压鸟窝恒阻锚索可与顶板耦合变形,可持续给顶板较大的支护作用力。工程应用后,11306运输巷顶底板、两帮变形量最大分别为191、105 mm,围岩变形控制效果显著。

煤矿液压支架与围岩强度耦合研究分析

针对大同机电装备有限公司中央机厂对7.0 m以上超大采高工作面开采时矿压显现剧烈、围岩控制困难、煤壁容易片帮、易发生顶板冒顶事故等问题,通过运用数值仿真、模型计算及实地测量方法对液压支架与围岩强度耦合性进行研究分析;通过对中央机厂15218工作面超大采高矿山压力测量分析,得出基岩厚度大、埋深浅的超大采高工作面具有明显的大小周期来压与动载矿压;通过对中央机厂15218工作面顶板的力学结构、支架支护阻力以及煤壁的力学结构、临界帮护力的研究,得出架型应选择两柱支撑掩护式液压支架,液压支架护帮结构应选择伸缩梁与护帮板分体结构;通过采用工程实践分析的方法对中央机厂15218工作面超大采高工作面液压支架进行了适应性评价分析,得出ZY21000/38/82D型液压支架可以满足中央机厂15218工作面超大采高工作面的实际生产要求。

The Boundary Element Method for Pile-Soil Interaction

In this paper, several mathmatical models for the pile- soil interaction are outlined. The Boundary Element Method is one of the very effective methods for the reasonable models of elasticity and elastoplasticity. The major of this paper is concerned with the Boundary Element Method for the pile-soil interaction, including general methods and calculating formulation of static and dynamic analysis of the pile and pile groups. Some results of analysis are also given.

基于流固耦合效应的高地应力软岩大变形隧道开挖稳定性分析

隧道施工过程中存在多场耦合效应问题,需研究耦合效应的影响。以蓝家岩隧道为工程背景,建立三维数值模型,基于流固耦合和不耦合工况,对比分析隧道施工过程中变形特征、初期支护受力特性及地层孔隙水压力变化规律。研究结果表明,考虑耦合效应下,隧道拱部沉降、洞周水平位移、底部隆起均较大;不考虑和考虑流固耦合效应下围岩与初期支护接触应力均为压应力,且分布特征相似,考虑流固耦合效应下围岩压力大于不考虑流固耦合效应下的围岩压力,高地应力软岩隧道施工时考虑流固耦合效应可更真实地反映支护结构受力状态;隧道开挖过程中围岩孔隙水压力增大,地下水易在隧道拱腰至拱脚位置涌出,需合理设计排水措施,并在拱底处进行降水。

极高地应力软岩稳定性指标优先级及多因素耦合分级

极高地应力隧道工程设计施工除了考虑地质构造作用极其强烈以外,强度应力比、地下水、膨胀应力、结构面产状等因素对围岩稳定性的影响也必须考虑,同时隧道轴线与最大应力主方向夹角、隧道断面及面积、岩层厚度及倾角等因素也非常重要。以《工程岩体分级标准》为基础,提出一种极高地应力复杂软岩隧道围岩稳定性因素优先级分析思路,并采用熵权法形成多主因素耦合、次因素修正的围岩分级方法。现场实践表明分级结果与现场施工状态吻合较好,进一步对另两座隧道使用本方法进行验证。结果表明,现行规范中围岩分级因素和方法不适用极高地应力情况,且和影响因素优先级加多因素耦合修正BQ值的围岩分级方法结果相差10%左右,原因是对极高地应力软岩稳定性影响因素考虑不全面。这种围岩稳定性分级方法具有较好的适用性,且耦合时使用熵权法原理使得结果更加偏向于定量计算,减少了人为因素干扰,结果更加客观真实。

热-力耦合作用对围岩塑性松动区的影响特性研究

针对高地应力区多场耦合作用对围岩塑性松动区的影响问题,依托实际工程,基于统一强度理论,建立多场耦合作用下围岩松动圈分析模型,研究初始地应力、地温、隧道开挖半径及中间主应力对围岩松动圈半径的影响。研究得到:1)热-力耦合作用下,围岩初始地应力对围岩松动圈半径的影响起主要作用,且围岩松动圈半径与初始地应力呈非线性关系;2)地温升高使初始地应力、隧道开挖半径及中间主应力影响系数对松动圈半径的影响变大;3)松动圈半径随着隧道开挖半径的增大而近似线性增大,随着中间主应力影响系数的增大而减小,中间主应力影响系数越小,围岩稳定状态对中间主应力越敏感;4)结合工程实例分析可知,在热-力耦合作用下,基于统一强度理论计算的围岩松动圈半径误差小于1.4%,证明所提出的计算方法是合理可行的。

高放废物处置库黏土围岩温度-渗流-应力耦合数值分析

深地质高放射性废物处置库运营过程中,围岩通常处在复杂的温度-渗流-应力多场共同影响的地质环境中,在温度-渗流-应力耦合作用下,合理地确定高放废物处置库硐室间距范围对处置库设计和长期安全稳定性评价尤为重要。基于国内外研究资料,针对塔木素预选区高放废物处置库黏土围岩,使用FLAC3D有限差分软件模拟计算了4种不同的硐室间距,并通过对围岩温度场、渗流场、应力场和变形场进行对比分析,对高放废物处置库硐室间距进行了优化。结果表明:在温度-渗流-应力三场耦合作用下,高放废物处置库黏土围岩相邻硐室间距最优设计值为10~12 m;当硐室间距小于10 m时,废物罐中心温度峰值超过了最高温度设计值100℃,当硐室间距大于12 m时,相邻硐室间的影响逐渐减弱,温度峰值逐渐趋近于单硐室。研究结果可为我国高放废物处置库黏土围岩硐室间距优化设计提供参考依据。

大跨度矩形巷道围岩失稳破坏机制及数值模拟

巷道围岩的失稳破坏是资源开采阶段面临的重要问题。首先,对巷道围岩失稳机制进行了理论分析,探究巷道稳定性的主要因素,并基于ANSYS/LS-DYNA仿真平台对不同跨度巷道(4、6、8、10 m)进行动静荷载耦合响应数值模拟分析。结果表明:当巷道埋深、底板梁厚度等因素一定时,巷道跨度是影响巷道围岩失稳的主要因素。巷道围岩在初始静应力场作用时,第一主应力随着跨度的增加呈现逐渐增大的趋势;跨度的增加(10 m)会使巷道围岩x和y方向的应力发生突增现象,均在巷道底板处有相对较大的拉应力。巷道跨度的增大,导致左右两帮的移近量有所增加;顶板下沉和底板隆起的程度显著增加,加剧巷道失稳破坏风险。在静动荷载耦合作用下,巷道围岩发生失稳破坏,破坏程度随跨度的增加而增加。

深井软弱围岩联合控制技术及耦合叠加拱承载效应研究

为有效解决深井软弱围岩巷道稳定控制技术难题,以淮南某矿-962 m轨道大巷为工程背景,依据软岩应力-应变曲线及围岩应力变化和强度之间的关系,建立圆形巷道围岩破坏分区力学模型,将开挖后的巷道由表及里依次划分为残余区、塑性软化区、塑性硬化区及弹性区,以阐明锚杆(索)锚固系统变形失稳机制,并提出深井软弱围岩的控制要点及关键技术。在此基础上,提出高预应力支护构件遏制残余区扩展、有效的支护承载区发挥围岩承载能力、极大提高软弱围岩承载强度及完整性、薄弱部位补强支护形成完整承载圈等4个围岩控制要点,进而提出“以高强预应力锚杆(索)为核心,浅、深孔分次注浆为基础,底角与底板锚注加固为关键”的全断面强化联合控制方案。结合支护方案特点提出实现内、外承载的“耦合叠加承载拱”结构。该耦合承载拱将支护体与围岩的相互作用和所提供的径向支护力相统一,对锚杆(索)支护阻力具有显著的放大作用。研究结果表明:围岩残余范围随硬化系数、软化系数、支护阻力及内聚力和内摩擦角的增大而减小,随扩容系数的增大而增大,而残余区、塑性软化区、塑性硬化区的边界发生渐进式扩展变换是导致围岩大规模破碎和锚杆(索)锚固失效根本原因。通过工程计算得到轨道大巷围岩屈服软化时的原岩应力阈值可达29.09 MPa,验证了支护方案的可靠性。轨道大巷经联合控制后围岩变形量仅为原支护参数下的12.6%~14.3%,在40 d后变形速率低于0.2 mm/d,实现了对巷道的稳定性控制。

爆炸荷载下刚-柔耦合围岩支护结构二维平板动态损伤破坏特征试验研究

为探究爆炸冲击荷载下以橡胶水泥砂浆(RCM)作为柔性吸能材料的“刚-柔耦合”围岩支护结构的动态稳定性,通过搭建二维平板爆炸冲击试验系统,开展单体平板试件在中心起爆方式下和组合体平板试件在偏心起爆方式下的单孔爆炸冲击荷载试验;并从炮孔动态膨胀响应特征、剥落区形成机理和爆生裂缝扩展机理3个方面,探究“刚-柔耦合”围岩支护结构二维平板试件的动态损伤破坏特征。最后,从应力波传播和协调变形2个方面分析讨论“刚-柔耦合”围岩支护结构中多层材料间的耦合作用特征与围岩稳定性机理,进一步印证以RCM作为柔性材料的“刚-柔耦合”围岩支护结构降低围岩及其支护结构动力损伤的潜力。研究结果表明:随橡胶体积分数增大,平板试件整体的损伤破坏程度明显减小;尽管RCM单体平板试件的爆后炮孔直径和剥落区面积因橡胶体积分数的增大而有所增大,但RCM有效降低了组合体平板试件的爆后炮孔直径、剥落区面积和爆生裂缝总长度。平板试件在爆炸冲击荷载作用下主要受到爆炸冲击波与爆轰气体的共同作用,尤其在底板对炮孔的封闭约束下,炮孔中也因爆炸能量的瞬间释放形成了向上的聚能射流效应,进一步导致了V形爆坑剥落区的形成。在同一起爆方向下,当橡胶体积分数为60%时,R-R-H和H-R-R的裂缝长度总和最小;在同一橡胶体积分数下,相比于H-R-R,R-R-H的裂缝长度总和最大降低了46.25%。