我国煤炭主体能源安全高质量发展的理论技术思考

【目的】为研究多源煤基固废胶结充填体的力学特性及变形破坏规律,选择5种典型煤基固废,开展了煤基固废胶结充填体(Coal-Based Solid Waste Cemented Backfill,CBSWCB)的单轴压缩、声发射响应及微观结构测试试验。【方法】分析了CBSWCB单轴抗压强度的影响因素和交互作用,建立了基于交互作用的抗压强度影响因素四维空间可视化模型,结合CBSWCB的声发射及微观结构特征,阐明了单轴压缩条件下的力学演化特征及宏观变形破坏规律,从微观角度进一步论证了CBSWCB承载过程中水化反应机理及宏细观联系。【结果和结论】试验结果表明：(1)单轴抗压强度的主要影响因素是质量分数,而炉底渣掺量的影响程度最小。(2)单轴压缩下CBSWCB的宏观变形破坏由塑性、弱劈裂破坏逐渐向脆性、剪切破坏转化。(3) CBSWCB试件声发射参数演化可以分为上升期、平静期、活跃期、稳定期,声发射累计振铃计数曲线呈现明显的“阶梯状”增长,累计振铃计数在上升期和平稳期内缓慢增加,在活跃期急剧增加,在稳定期逐渐趋于平缓。(4)水泥掺量偏低以及多源煤基固废充填材料属性差异导致水化反应程度有限,水化产物数量较少是CBSWCB单轴抗压强度普遍偏低的主要原因。研究结果可为多源煤基固废用于充填开采提供一定参考依据。

     

顶板离层水突涌模式及预防技术模拟研究

为预防顶板离层水突涌产生的安全事故,提出了部分充填方案进行模拟研究。首先通过现有资料总结分析全国发生的多种离层水害事故,深入研究离层积水致灾模式;然后以陕西某矿首采区1307工作面的离层水害事故为例,分析其水文地质条件、上部含水层和离层水突涌的关系,利用3DEC数值软件模拟工作面顶板离层空间发育特征;最后根据该矿的实际情况,提出部分充填开采方式预防离层水突涌的技术措施,并对该矿的部分充填方案进行优化模拟研究。研究结果表明：根据发生条件的不同将离层水突涌划分为5种模式,离层积水过程分为初始积水期、积水至满期和裂隙扩展期;在保持充填率不变的情况下,随着走向采宽和充填宽度的同时同量增加,充填体对上覆岩层支撑作用逐渐增强,离层下部隔水层出现两侧应力增大现象,最佳部分充填方案为采宽80 m,充填宽度80 m,为顶板离层水害的预防提供新的思路。     

陶粒粉煤灰混凝土在桥涵台背回填中的应用研究

通过材料性能试验、土工离心模型试验和数值计算,研究陶粒粉煤灰混凝土的物理力学性能及其在桥涵台背回填的应用效果。首先,通过材料性能试验研究不同配合比的陶粒粉煤灰混凝土的物理力学性能;其次,通过土工离心模型试验和数值计算研究陶粒粉煤灰混凝土用作桥涵台背回填材料时,作用于台背的土压力和回填体的变形特性。研究发现：陶粒粉煤灰混凝土具有轻质、高强度、高模量和易施工等诸多优点;陶粒粉煤灰混凝土回填体作用于台背的土压力明显小于常规回填材料;回填区和地基的沉降变形亦明显小于其他材料。结果表明：陶粒粉煤灰混凝土作为台背回填材料具有明显的优越性,是一种值得推荐的桥涵台背回填材料。     

宜昌市北海路隧道塌方处理技术

通过宜昌市北海路隧道塌方处理施工的实例，分析了造成塌方的原因，提出并实施了钢拱架、锚喷网复合支护结构塌方处理方案，并对塌空区的回填方案进行了比对，优选泵送陶粒砼加固的新工艺，取得了较好的回填加固效果。通过监控量测成果分析证明了采用陶粒砼工艺大大减轻了回填砼的质量，从而减小了对钢拱架支撑、锚喷复合支护结构的压力，确保回填砼及钢拱架支撑、锚喷复合支护结构的稳定性，确定二次砼衬砌施作的时间。     

Hydraulic and Thermal Conductivities of Kaolin–Silica Mixtures under Different Consolidation Stresses

Stable backfill materials for the heat sensitive structures of buried power cables, hot water pipes, and gas pipelines are suggested to have low permeability and high heat transfer characteristics. The hydraulic and thermal conductivities of backfill materials or clay liners are important parameters in proper design and construction of geotechnical structures involved with heat transfers. In this study, to investigate the optimal natural backfill or liner materials, thermal and hydraulic conductivities of kaolin–silica mixtures examined based on the results from laboratory tests under different consolidation conditions. From the experiment results, the thermal conductivity increases while hydraulic conductivity decreases with increasing density during consolidation process. As a result, back-fill materials with high kaolin content under low consolidation stress were desirable materials for burial of heat sensitive structures.     

Lateral stress caused by horizontal and vertical surcharge strip loads on a cross‐anisotropic backfill

This study derives analytical solutions for estimating the lateral stress caused by horizontal and vertical surcharge strip loads resting on a cross‐anisotropic backfill. The following loading types are employed in this work: point load, line load, uniform strip load, upward linear‐varying strip load, upward nonlinear‐varying strip load, downward linear‐varying strip load and downward nonlinear‐varying strip load. The cross‐anisotropic planes are assumed to be parallel to the horizontal surface of the backfill. The solutions proposed herein have never been mentioned in previous literature, but can be derived by integrating the point load solution in a Cartesian co‐ordinate system for a cross‐anisotropic medium. The calculations by the presented solutions are quick and accurate since they are concise and systematized. Additionally, the proposed calculations demonstrate that the type and degree of material anisotropy and the horizontal/vertical loading types decisively influence the lateral stress. This investigation presents examples of the proposed horizontal and vertical strip loads acting on the surface of the isotropic and cross‐anisotropic backfills to elucidate their effects on the stress. The analytical results reveal that the stress distributions accounting for soil anisotropy and loading types are quite different from those computed from the available isotropic solutions. Restated, the derived solutions, as well as realistically simulating the actual surcharge loading circumstances, provide a good reference for the design of retaining structures for the backfill materials are cross‐anisotropic. Copyright © 2005 John Wiley & Sons, Ltd.     

Temperature dependence of the reactivity of cemented paste backfill

The environmental performance of cemented paste backfill (CPB; a mixture of tailings, water and binder), which contains sulphide mineral-bearing tailings, is strongly influenced by its reactivity. However, our understanding of the reactivity of CPB under various thermal loading conditions as well as its evolution with time is limited. Hence, a laboratory investigation is conducted to study the effects of curing and ambient (atmospheric) temperatures on the reactivity of CPB. Oxygen consumption (OC) tests are conducted on CPB specimens cured at different temperatures to study their reactivity. Furthermore, microstructural analyses (e.g., x-ray diffraction (XRD), mercury intrusion porosimetry, and thermogravimetry/derivative thermogravimetry) are performed to assess the microstructural characteristics of the tested CPBs. The results show that the reactivity of CPB is temperature-dependent. As the curing temperature increases, the reactivity generally decreases. The reactivity is also affected by the ambient temperature. The reactivity increases as the atmospheric temperature increases. However, the extent of the effect of the temperature depends on the curing time and is generally more pronounced at the early ages. Furthermore, the presence of sulphate in the pore water of CPB can significantly affect the reactivity of CPB cured at high temperatures (50 °C). The findings of this study will therefore help to better assess and predict the environmental behavior of CPB under various field thermal conditions.     

单轴压缩胶结充填体声发射参数时空演化规律及破裂预测

为了研究胶结充填体在荷载作用下的时空演化规律,利用WAW?300微机电液伺服万能试验系统与DS2系列全信息声发射监测系统,监测了胶结充填体试样在单轴压缩过程中的应力、应变变化规律和声发射活动,根据振铃计数率、能率的阶段性特征,将加载过程声发射参数变化规律分为3个阶段:上升期、平静期和活跃期,进而研究声发射参数时空演化规律;并利用振铃计数率、能率参数,结合尖点突变理论,进行胶结充填体破裂预测。研究表明:(1)单轴压缩条件下,胶结充填体属于延性破坏,裂纹贯穿属于剪切贯穿;(2)通过声发射参数演化规律及定位演化特征,分析得出胶结充填体在加载中是由局部破坏向整体失稳演化;(3)运用尖点突变理论进行胶结充填体破裂预测,并构建了破裂预测模型,预测结果与试验结果一致。研究结果可为人工矿柱稳定性监测和破裂预测提供依据。     

大面积软弱地基浅层处理技术研究

结合上海市某工程地基加固实践,对无填料振冲法加固饱和疏松粉细砂地基和井点降水联合低能量强夯法加固粉细砂及下卧扰动软粘土地基的两种技术进行了介绍,经过加固处理的地基均达到设计要求。通过对加固效果进行的分析得出一些有意义的结论,为类似地基处理提供了参考依据。     

盾构隧道监测土压力匹配误差分析

盾构隧道施工中采用了特殊的工艺——壁后注浆,包裹了隧道表面预埋设的土压力计,壁后注浆对土压力计的包裹将影响其监测结果的可靠性。在注浆体力学试验基础上,建立能考虑注浆体固结硬化过程的有限元模型,探讨注浆体层的包裹对土压力计监测结果的影响。注浆体注入盾尾空隙后,终凝前处于流动状态,具有较强调节土压力计部位局部土体不均匀沉降和畸变应力场的能力,监测土压力与实际较为接近,其匹配误差远小于通常地下结构表面监测土压力的匹配误差。