Effect of the Ratio Between Wavelength and Diameter of Hole on the Stress Distribution During Passage of a Stress Pulse

This paper has studied the effect of ratio between wavelength and diameter of hole on the stress distribution around hole during passage of a triangular stress pulse by using dynamic finite element code. The computations for seven different ratios between wavelength and diameter of hole have carried out. Besides the complete curve of variations of dynamic stress concentration factors with the ratios the changes of whole stress field around hole were obtained, particularly, the variations of values and distribution regions of radial and tangential tension stresses around hole. In addition, the effect of the length of pulse front (rise from zero to peak) was considered and the comparisons of the stress distributions around hole during that the peaks of two stress pulses of different wavelengths pass a hole with the corresponding static cases have been made.     

高压脉冲放电技术对桩径影响的研究

高压脉冲放电技术可利用液电效应产生的冲击波,在钻孔局部产生扩孔段,通过灌注水泥而形成异径扩底桩。主要介绍了高压脉冲放电技术的扩底成桩机理、成桩过程以及对桩径的影响情况,并研究了冲击波、蒸汽膨胀压力对桩径的作用。利用新引进的高压脉冲放电装置进行现场试验,试验结果表明,理论公式计算结果基本与试验结果符合。     

Stress Distribution During Extraction of Pillars in a Thick Coal Seam

Summary This paper presents field observations on distribution of vertical stress during an experimental trial of extraction of pillars in four panels in 6.0–8.0m thick coal seam, as a part of a Science and Technology project funded by the Ministry of Coal, Govt of India. Variation of induced stress based on continuous monitoring data for the first time in Indian coal mining scenario showed distinct anomalies and potential for better understanding of strata mechanics and warning of major roof falls during pillar extraction. Numerical model studies based on finite difference code – FLAC were also conducted for stress analysis in idealized pillar mining sequence so that the influence of each stage of extraction could be identified. The numerical model results on stress concentration over the pillars, stooks and ribs showed variation of 3.6%, 8.3% and 6.1%, respectively as compared to the field observations for 7m thick coal seam at a depth cover of 60m from the surface. This indicates validity of the numerical models for stress analysis in the simulated conditions of the present field experiments.     

大口径钻孔桩孔壁稳定分析研究

从理论上分析并结合实践经验 ,提出了大口径钻孔桩孔壁稳定的 3个条件 ,即静力平衡、地质渗流、时间因素 ,在此基础上分析了影响孔壁稳定的各种客观、工艺、环境及人为因素 ,给出了预防和处理孔壁坍塌事故的措施。     

一起大直径深孔复杂事故处理实践

着重论述了一起大直径深孔卡埋钻复杂事故的处理,对事故发生过程和处理方法等作了详细的阐述,总结了一些经验和体会。     

宁夏羊场湾煤矿复杂地层大口径电缆孔施工技术

结合神华宁煤羊场湾矿电缆钻孔施工实践,总结出宁东煤矿大口径特种钻孔施工的最佳工艺与技术要求,有效预防和处理破碎地层漏失的方法;在大口径钻孔水泥固井工序施工中成功使用了先进的止逆单向阀固井工艺,提出了针对大口径钻孔孔内事故的处理方法,并进行了成功的应用。     

差应力对闪长岩部分熔融熔体分布和成分的影响

探讨差应力对熔体分布和成分演化的关系,利用细粒闪长岩进行高温高压条件下的岩石变形,主要包括静态熔融实验和有差应力参与的动态熔融2种类型。实验首先统计了熔体含量、确定了实验重要参数,然后分别描述了动、静态熔融实验后闪长岩的显微特征;并且通过对动、静态熔融实验结果熔体分布情况的对比,结合熔体成分电子探针数据进行分析。结果表明:在细粒闪长岩的部分熔融中,熔体在差应力的作用下沿一定的方向展布,并从差应力大的地方向差应力小的地方运移,差应力的作用使得高含水矿物(角闪石)先于熔点低的斜长石发生熔融,说明差应力促进了岩石的熔融,使得熔体成分向Si、Al等方向转化,即从基性向酸性转化。     

强夯时地基土的应力场分布特征及应用

在前期研究工作的基础上,利用积分变换技术和传递矩阵法对强夯时地基土的应力场分布特征进行了数值模拟,并和前人的数值分析与室内外试验结果进行了对比分析,结果表明：所得的动应力衰减规律与实测结果较为吻合。在动荷载作用下,地基土动应力衰减率比强夯冲击荷载作用下的衰减率快,强夯冲击荷载作用下的最大动应力等值线图可作为估算强夯的有效加固深度和加固范围时参考。     

大直径钻孔灌注桩质量检测方法和存在的问题

阐述了大口径检测的重要意义,分析了目前大口质量检测的方法和存在的问题,并指出了解决这些问题的方法和途径。