【作者】 李为腾；

【导师】 仝兴华； 李术才；

【作者基本信息】 山东大学 ， 工程力学， 2014， 博士

【摘要】 煤炭是我国的主体能源,随着浅部资源的枯竭,煤炭开采进一步向千米及千米以上深部发展,截止到2014年,我国开采深度超过1000米的矿井已达到50处左右,由于岩体力学自身固有的复杂性,同时加上深部、软岩、构造等特殊条件的影响,巷道的变形破坏机理仍然不够明确,巷道大变形、破坏、冒顶等现象仍然较为常见,目前常用的支护方式如锚网喷、U型钢拱架等不能满足需要,围岩稳定性控制理论及技术仍然亟需改进和完善。在此背景下,本文主要进行了以下研究工作并取得部分有益结论。(1)围岩承载结构失效机理现场探测及试验研究通过探测和监测分析掌握了深部软岩巷道典型的围岩变形破坏规律及支护构件失效规律。基于探测结果,进行了数值试验研究,讨论了支护强度、地应力等级、围岩强度等级三个因素对巷道稳定性的影响规律；在现场探测和数值试验基础上从锚网喷支护的局限性和高刚、高强度支护的必要性两个方面分析了深部软岩巷道围岩承载结构失效机理：在没有足够的径向支护强度的条件下,围岩的自承结构较难形成,同时支护结构也极易失效,围岩很难形成稳定有效的承载结构；具有一定刚度和强度的拱架是一种行之有效的解决途径,是必要的且拱架强度有一个合理值。基于上述分析,提出了深部软岩巷道“高强完整让压”支护理念。(2)约束混凝土定量让压支护体系研究在充分的现场调研和现状分析的基础上,针对深部、软岩难支护巷道,根据“高强完整让压”支护理念,研发了定量让压约束混凝土拱架技术体系,核心构件为具有定量让压节点的约束混凝土拱架,重点研究了方钢约束混凝土(下文简称SQCC)拱架和U型约束混凝土(下文简称UCC)拱架。该技术体系具有强度高、刚度大、定量让压的特点,适用于各种深部、软岩、构造、渗涌水等特殊地质条件下的巷道支护。(3)约束混凝土拱架计算理论研究①建立了约束混凝土拱架套管节点的力学分析模型,对套管节点的力学行为进行了分析；从理论上推导了套管节点的铰-刚临界角度ω0的计算公式,研究了不同参数对其的影响规律,得到了拱架套管节点铰-刚判据；对套管受力进行了分析,对其强度和刚度进行了计算分析与校核,同时计算了UCC拱架可缩性节点的等效惯性矩(等效刚度)。②采用力法推导了任意节数的圆形、直腿半圆形拱架的内力计算公式和节点铰接模式下3节直腿半圆形拱架的内力和节点转角计算公式；讨论了荷载q1、侧压力系数λ、节点定位角a、节点等效刚度EI’、高径比κ等参数对拱架内力的影响规律。③分别计算或拟合分析了SQCC构件、UCC构件、CCC构件、工字钢构件和U型钢构件的压弯极限承载力计算公式,对拱架极限强度承载力进行了对比分析：侧压力系数λ为1时,SQCC150×8和UCC29拱架极限强度承载力为1.OMPa左右,是常规U36拱架的1.81倍。④利用封闭圆拱的临界荷载计算公式,分析了不同截面形式的拱架失稳临界荷载：UCC29失稳临界荷载为0.45MPa,是U29圆拱的1.88倍；SQCC150×8圆拱是相同用钢量U36圆拱的1.62倍。⑤利用阶梯折算法,对四套管拱架稳定性进行了计算分析,并讨论了不同套管刚度和长度对拱架稳定性的影响规律。(4)约束混凝土基本构件力学性能试验①进行了U型钢、UCC和SQCC短柱的轴压试验,UCC短柱和SQCC短柱呈现整体的塑性失稳,避免了常规U型钢短柱的弯曲失稳破坏,极限轴压承载明显提高,且具有较好的后期承载能力；短柱构件设置灌注口,构件产生侧倾失稳破坏,极限承载力降低,经过补强后,构件极限承载力恢复；通过试验数据分析得到UCC29构件极限承载力与封板厚度t和混凝土强度等级fcu,k的关系表达式；采用声发射手段对内部混凝土响应特征进行了研究,为内部混凝土承载及破裂行为研究提供了有力手段；采用ABAQUS数值计算软件,进行了短柱构件的数值试验,计算结果与室内试验具有很好的一致性。②建立了套管节点的纯弯曲数值计算模型(SQCC150×8),定义了套管节点的有效长度(或计算长度)l0临界曲率增量△φ0、临界转角ω0,得到了约束混凝土套管节点不同于常规约束混凝土纯弯构件的典型4阶段M一△φ曲线,对比分析了约束混凝土套管节点的力学行为模式和临界转角、极限弯矩、抗弯刚度等力学参数；应力分析显示反弯对弧形构件核心混凝土是一种较为不利的状态；讨论了各不同参数(混凝土强度fcu,k、套管长度l、套管壁厚t、间隙δ等)对其极限弯矩、临界曲率增量、等效抗弯刚度等力学参数的影响规律,为套管参数设计提供支撑。③进行了UCC29直构件和弧形构件正弯和反弯的四点纯弯曲数值试验,得到了UCC29构件典型M-△φ曲线,发现正弯和反弯对于UCC构件力学性能有影响,构件的原始曲率对其能基本没有影响；正弯对UCC构件核心混凝土是一种较为不利的状态。④进行了UCC长柱偏压研究,得到了不同参数下构件的轴力-横向位移曲线；正偏压及轴压情况下UCC29构件的极限轴力是U29构件的1.4-1.6倍,负偏压情况下是2.2～2.6倍；拟合得到UCC29构件(封板厚10mm,C40)的压弯承载力计算公式并用于拱架理论计算。⑤进行了UCC29和SQCC150×8常规偏压柱、带灌注口偏压柱和灌注口加强偏压柱的试验研究；对比分析了变形形态、极限承载力、应力分布、补强效果等；SQCC150x8构件M-N曲线与理论计算结果基本一致,验证了理论计算的正确性。通过以上研究较为全面地掌握了约束混凝土构件的力学承载特性,为进行拱架选型及参数设计提供了参考数据。(5)约束混凝土拱架承载特性试验研究采用自主设计研发的地下工程约束混凝土拱架1：1大型力学试验系统,进行了UCC和SQCC两类约束混凝土拱架的力学试验,通过对拱架的荷载、变形、应力进行系统采集和分析,深入研究了各组拱架的变形失稳形态、局部破坏特征、整体受力规律及拱架节点受力变形特征。进行了数值试验研究,与室内试验结论相互验证补充。得到以下主要结论：①均压下直腿半圆形拱架的变形形态一般为“拱顶上升,拱腿内敛,整体变瘦高”；试验结束时一般在拱腿起拱点附近发生最大变形,有时伴随明显的强度破坏现象；在侧压系数为0.5的情况下,拱架变形形态为“拱顶下沉,拱腿基本不变,整体变矮”。②SQCC150x8拱架和UCC29拱架极限承载力比U36拱架和U29拱架显著提高,是U36拱架的1.4倍～1.7倍左右;随着混凝土强度的提高,拱架极限承载力增大,SQCC150x8-C50拱架极限承载力比核心混凝土为C40和C30时提高7.4%和12.6%。在UCC29拱架中,影响程度相对较小。③在侧压系数λ=0.5、1.0和2.0三种情况下,随着侧压力系数的增大,拱架极限承载力出现明显降低；UCC29拱架λ为1.0和2.0时的极限承载力分别是λ为0.5时的80%和48%；SQCC150x8拱架λ为1.0和2.0时的极限承载力分别是λ为0.5时的59%和39%。④本文试验拱架的整体屈服是由于构件截面(一般是截面弯矩最大的起拱点位置附近)强度破坏引起的,继而发生了整体的失稳破坏。均压作用下的圆形封闭拱架,对截面抗弯刚度要求更高；而直腿半圆形拱架,对于截面的压弯极限承载力要求更高。⑤SQCC150x8-C40拱架在套管节点处安装的定量让压装置,起到了较好的让压作用,与让压装置的室内试验结果相吻合,两阶段让压后,左侧和右侧套管内的让压量分别为93.5mm和88mm,可增强拱架抵抗深井高应力围岩压力的作用。(6)支护体系现场试验研究选择巨野矿区典型千米深井,对UCC拱架支护体系、SQCC拱架支护体系及对应的U型拱架壁后充填支护体系进行了对比研究,对各方案围岩控制效果、拱架受力特性与壁后充填混凝土力学响应进行了研究,UCC支护体系和SQCC支护体系的巷道平均变形量仅为U型钢拱架支护巷道的20.6%和28%,具有相对更高的承载能力及安全储备。现场试验进一步印证了约束混凝土支护系统的优势性,提高了支护体系的整体稳定性,调动围岩自承能力,有效保证了巷道的稳定。通过上述各方面的综合研究,明确了深部、软岩巷道围岩变形破坏机理,掌握了约束混凝土拱架的力学性能和承载特性,通过现场试验研究证实了约束混凝土拱架支护体系显著的围岩控制效果,最终形成了一套完整的深部软岩难支护巷道围岩控制体系及配套计算理论。更多还原

【Abstract】 Coal is the main energy in China, with the exhaustion of shallow resources, the coal mining depth is growing and some coal mines is deeper than1000meters. By2014, there are more than40coal mines whose mining depth is much more than1000m in China. Because of the complexity of rock mechanics and the influence of special conditions such as deep mining and soft rock, the deformation and failure mechanism of roadway is still unclear, the roadway failure phenomenons such as large deformation and roof caving are common. The support methods commonly used such as anchor net spray support cannot meet the requirements, and the stability control theory and technology still needs to be improved and perfected. Against this background, the following study work is carried on and some conclusion has beem got.(1) Field detection and test study on the failure mechanism of surrounding rock bearing structureThe typical deformational and destructive law and supporting structure failure law of soft rock roadway at great depth are analysed according to detecting and monitoring. Numerical experimental study is carried out based on the detection results, and the influence of the support strength, crustal stress grade and surrounding rock strength grade to roadway stability is discussed. The failure mechanism of surrounding rock bearing structure of soft rock roadway at great depth is analysed in terms of the limitation of anchor net spray support and the necessity of high rigidity and high strength support. Surrounding rock bearing structure is hard to form or is easy to failure while the radial supporting strength is not enough; arch center with certain rigidity and strength is very useful and necessary, and the strength has a reasonable value. A supporting idea for the soft rock roadway at great depth is presented based on the above analysis.(2) Study on the quantitative yieldable confined concrete supporting systemOn the basis of the field research and status analysis, aimed at the typical issues of softrock roadway supporting at great depth, and according to the presented supporting idea, a quantitative yieldable confined concrete arch support system is invented. The core member of this system is confined concrete arch center with quantitative yieldable jionts. This paper mainly introduced the rectangular section confined concrete arch center and U-steel confined concrete arch center. This technology system has the characteristics of high strength, high rigidity and quantitative yielding, and it can be used for the roadway supporting under difficult geological conditions.(3) Theoretical study on the calculation of confined concrete arch center①The calculation model of confined concrete arch casing jiont is built, and the mechanical behavior of casing jiont are analysed. The formula of hinge-rigid critical angle ω0is deduced theoretically, and the influence law of different parameters is studied and the criteria is obtained. The force and rigidity of casing is calculated and the equivalent inertia moment (equivalent rigidity) of yieldable jiont on UCC arch is obtained.②The inner force expressions of circle and straight wall semicircle arch is deduced with the force method, and the node rotation angle calculation formula under the node articulated model is deduced too. The influence law of arch inner force by different parameters such as load, lateral pressure coefficient, location of jiont, equivalent rigidity of node, ratio of height to diameter.③The ultimate bearing capacity calculation formula of SQCC member, CCC member, UCC member, I-steel member and U-steel member under compression-bending is deduced. Comparative analysis of arch ultimate bearing capacity on strenth is carried out:when side pressure coefficient is1, the ultimate strength bearing capacity of SQCC150×8and UCC29arch center is about1.0MPa, which is1.81times of U36arch center.④Based on the calculation formula of circular arch instability critical load, the instability critical load of different section arch is analysed. Instability critical load of UCC29is0.45MPa, which is1.88times of U29arch; the number of SQCC150*8arch is1.62times of U36arch (the steel consumption is same).⑤The stability of four casing jionts arch center is analysed with the Step convert method, and the influence law of different rigidity and length of the casing to the arch stability are discussed.(4) Mechanical property tests on basic members of confined concrete arch①The axial compression experiments of U-steel, UCC and SQCC short column are carried out. The UCC and SQCC short columns present holistic plastic instability, avoided the bending instability failure morphology of U-steel short column. And the bearing capacity are improved greatly. Unstable failure occurs when the pour hole is installed, and the bearing capacity decreased. At the same time the ultimate bearing capacity recovered when the pour hole is reinforced. The relational expression between the ultimate bearing capacity of UCC29and the shrouding thickness t and the concrete strength grade fcu,k is obtained. And the response characteristics of inner concrete is studied with acoustic emission, which is very useful to the study of inner concrete bearing and failure characteristics. The ABAQUS software is used for numerical experiments of short column members, and the calculation results have good consistency with the laboratory test.②A pure bending numerical model of casing jiont is built, length lo, critical curvature increment△φ0and critical angle ω0of the casing jiont are defined. And the typical4-step M-△φ curve of confined concrete casing jiont is obtained. The mechanical behavior patterns and mechanical parameters are analized. The stress analysis shows that the reverse bending is a bad state to core concrete in curved member. The influence laws of different parameters to different mechanical parameters such as ultimate bending moment, critical curvature increment and equivalent bending rigidity are discussed. The above results provide basis for the design of casing parameters.③The four-point pure bending tests of UCC29members under positive bending and negtive bending are carried out and the typicalM-△φcurve of confined concrete casing jiont is obtained. The bending direction do has effect on mechanical properties of UCC member, and the positive bending is a bad state to core concrete in UCC member.④The eccentric compression of UCC long columns is studied and the axial force-lateral displacement curves with different parameters are obtained. The ultimate axial force of UCC29is1.4-1.6times of U29with positive biasing, and the number is2.2-2.6with negative biasing. The compression bending capacity formula for UCC29members is matched and has been used in the calculation theory of arch.⑤The experiments of eccentric loading columns, eccentric loading columns with pour hole and strengthen eccentric loading columns are studied, and the alternate form, ultimate bearing capacity and stress distribution are analyed contrastively, the N-M curve is consistent with the theoretical calculation results, and the correctness of the theoretical calculation is verified.The mechanical bearing characteristics of confined concrete members is mastered according to the above studies, the reference data for arch center type selection and parameter design is provided.(5) Experimental study on the bearing characteristics of confined concrete arch centersThe mechanics experiment of UCC and SQCC arch center are carried out by using designed mechanics test system of confined concrete arch center underground. Based on the collection and analysis of arch load, deformation and stress, the instability deformation, local failure characteristics and deformation characteristics of arch centering nodes are studied. Numerical experimental study is applied to verify the conclusion based on the laboratory experiment. The main conclusions are summarized as follow:①The deformation of straight wall semicircle arch under uniform pressure commanlly is’rise at top of arch, convergence at leg, slimer and taller on the whole’. The position with maximum deformation is always spring or nearby, and along with strength failure sometimes. The deformation of arch under pressure which lateral pressure coefficient is0.5is’settling at top of arch, non-deformation mainly at leg, lower on the whole’.②The ultrmate bearing capacity of SQCC150×8and UCC29arch centering is much higher than U36and U29arch centering, is1.4-1.7times of U36arch. The ultimate bearing capacity of SQCC150×8-C50is7.4%and12.6%higher than the one with concrete strength C40and C30. The trend is not so significant in UCC29arch.③The ultramate bearing capacity is drop along with the increase of γ (γ=0.5,1or2). The ultimate bearing capacity of UCC29-C40arch with γ,=1.0and2.0is80%and45%of the one with γ=0.5respectivty, and the number of SQCC150x8arch is59%and39%.④The overall yield of the arches in this experiment is caiused by strenth failure, and the overall bulkling happened afterwards. The circular arch under uniform pressure demands higher bending rigidity for bearing, and the straight wall semicircle arch demands higher eccentric compression bearing capacity instead.⑤The quantitative yielding devices at the casing jionts of SQCC150x8-C40arch center have good effect, and consistent with the laboratory test results. The yieldable devices can strengthen the capacity of arch agianst surrounding rock pressure in deep roadway.⑥Field experiments on support systemThe typical mines of Juye mining area is selected to study on SQCC and UCC arch center system. Based on the analysis of surveillance results of deformation, radial force, strain of arch center steels and stress of filled concrete, the SQCC and UCC arch center have remarkable effect on surrounding rock control under the conditions of soft rock roadway in the km deep mine and fault fracture zone:Both of the amount of roof subsidence and two sides convergence are less than20mm, supporting effect is much improved compared with U-steel arch center.According to the comprehensive studies above, this paper defined the deformation failure mechanism of surrounding rock under the typical conditions of deep and soft rock, mastered the mechanical properties and bearing capacity of confined concrete arch center. The remarkable effect on surrounding rock is proved by field experiment study. Finally, a complete surrounding rock control system of soft roadway in deep mine with matching calculation theory is built and improved.更多还原