岩土体变形破坏机制及井筒破裂模式

以淮北临涣矿区为例,在详细调查分析了破裂井筒的矿井水文地质与工程地质条件及其它背景资料的基础上,根据矿区底含土体及煤系基岩风化带变形破坏的影响因素及形成过程,本文首次论论了岩土体变形破坏的四个发展阶段和井筒破裂的四种模式及其间的关系,并揭示了井筒破裂的,从而为防治井筒破裂和评价井筒稳定性提供了依据。     

地层失水沉降诱发井筒破裂治理效果的三维数值分析

运用三维有限差分软件FLAC3D对破裂井筒的各种治理措施进行了数值模拟,分析评价了钢圈加固和喷射混凝土套壁、壁后注浆、地面注浆、开设卸压槽等各治理措施的工程效果。结果表明,钢圈加固和喷射混凝土套壁强度相对较小,适合紧急的抢险处理和防止破裂混凝土坠落,难以维持井壁的长期稳定;破壁注浆措施在一定程度上控制了井壁与土层相对位移的增大,防治井筒破裂效果良好,且预防性壁后注浆效果更为突出;地面注浆防治效果明显,在注浆孔数量不变的条件下,孔位的合理选择对保证地面注浆防治效果至关重要;卸压槽可以有效吸收纵向变形以抑制破裂井壁的发展,其开设在破裂处上部时,效果最好。分析结果可用于指导破裂井筒治理的设计与施工     

中国东部黄淮地区煤矿井筒成片破裂研究

自80年代以来,中国东部黄淮地区许多生产矿井的立井井筒相继出现了程度不同的破裂,对煤矿的安全生产造成威胁.在详细调查的基础上,本文首先归纳了该地区井筒破裂的特征,主要有:(1)井筒破裂段大多位于上覆表土层与基岩交界面附近上下数米之内;(2)井筒破裂时间基本集中在1987年之后的短短几年内,与矿井投产时间长短无对应关系;(3)破裂过程一般是内井壁先出现裂缝,后掉混凝土块,渐渐露出已弯曲的钢筋,最后出现环形带状破裂;(4)井内设备变形明显滞后于井壁破裂.本文介绍了近年来我国学者有关井筒成片破裂机理的研究情况,以及对破裂段采取的加固方法及效果.根据其中一个井筒破裂最为严重的煤矿进行的井下原地应力测量结果,考虑当地地质资料,进行了地应力场有限元模型分析.结合区内地震活动、新构造运动的若干表现以及地壳应力、形变观测对井筒破裂的原因进行了综合分析,认为新构造运动引起的水平构造应力增高可能是黄淮地区井筒成片破裂的主要因素,区内特殊的底含结构及采动引起的四含水流失可能是井筒出现破裂的诱发因素.     

兖腾—徐淮矿区地应力与井筒破裂关系研究

煤矿立井非采动破裂是一种矿井地质灾害,但对于立井破裂的原因有着多种认识,兖腾—徐淮矿区井筒发生破裂后,有一种观点认为造成井筒破裂的原因是该区内水平构造应力大所致,根据该矿区地应力与井筒破裂关系进行的分析研究,论证了该矿区的井筒破裂与水平构造应力并不存在着很密切的联系。     

厚冲积层立井井筒非采动破裂过程的三维耦合数值模拟

立井井筒破裂时,在底含、基岩、井筒之间包含三个同时发生的变化过程(1)底含水由基岩向矿井中的渗流;(2)深厚表土底部含水层的失水固结沉降与井壁附加力的产生;(3)立井井筒在附加力的作用下发生变形.本文采用拉格朗日元法对立井井筒的破裂过程进行了数值计算,且设置了界面单元来计算土与井筒之间的相互耦合作用,其计算结果揭示了立井井筒破裂过程中各个影响因素之间的变化规律,对于立井井筒破裂的机理分析及预防治理具有重要意义.     

基于连续损伤的水平井射孔-近井筒三维破裂模拟

射孔作为井筒与储层之间的液流通道,是水力压裂过程中的重要可控性参数。为研究水平井射孔-近井筒破裂机制,采用岩层变形-流体渗流方程描述应力状态变化,应用连续损伤破裂单元表征三维破裂位置与形态演化,并开发有限元求解程序模拟分析了射孔对水平井初始破裂压力、破裂位置及近井筒裂缝复杂性的调控作用。通过与解析模型及射孔压裂物理模型试验结果对比,验证了模型及有限元程序的有效性;水平井破裂压力数值分析结果与现场测试数据吻合较好。研究表明：射孔可调控水平井破裂压力与初始破裂位置,同时对近井筒区域裂缝扩展形态影响显著。通过优化射孔参数可以引导初始破裂向最优破裂面扩展、有效降低破裂压力,减小由于螺旋射孔空间排布引起的水平井近井筒裂缝迂曲与复杂程度,提高致密油气藏压裂改造效果。     

武山铜矿南副井井筒破裂分析与注浆加固

介绍了武山铜矿南副井井筒破裂的情况，从地质因素和地下水动力因素2方面对该井筒破裂的形态及原因进行分析，并对井筒破壁注浆加固施工工艺及效果进行了阐述。     

巨厚新生界矿区井筒破坏的地质因素及对策

在两淮、徐州、大屯等矿区先后发生了多起井筒破裂事故,严重影响了矿井的安全和正常生产。该文在分析已产生井筒破坏矿区其水文地质工程地质条件及井筒破坏特点的基础上,论述了井筒破坏的地质因素及力源,提出了选择较好的井筒位置、减少井筒处新生界水位降低值、防止井筒外跑漏水、局部加固底部含水层,开展井筒监测及井筒垂直压力预测等防治对策。     

鲍店煤矿主副井筒破裂原因及防治对策

鲍店煤矿主副井筒变形破裂,严重威胁矿井安全,经济损失巨大。通过观察分析,认为变形破裂乃第四系水位下降引起的地面沉降所致,并据此提出了防治对策。      

煤矿立井井筒非采动破裂的人工神经网络预测

应用人工神经网络的基本原理,建立了一个基于神经网络的煤矿立井井筒非采动破裂的预测系统,实现了立井井筒破裂预测的智能化。最后将神经网络预测结果与数值计算结果对比,认为应用人工神经网络对立井井筒破裂时间的预测比较准确、实用。     

排水抗滑桩技术研究现状及展望

排水抗滑桩技术一方面可以克服传统抗滑桩不利于坡内渗流排水这一问题,另一方面也减少了竖向排水、抗滑等结构单独施作时的开挖工程量,并可充分提供水化热散热面,确保整体结构的质量,因此成为现代滑坡防治工程中重要的技术手段,也是近年来地质灾害、水文地质及地下工程等学科持续关注的新型技术。排水抗滑桩技术涉及流体力学和固体力学,以及水动力模型、结构模型、工程地质模型等,理论体系尚不够成熟,且存在空间结构组合相对复杂、施工技术难度较大等问题,其进一步推广应用受到制约,需要开展有针对性的现状总结研究。在查阅大量国内外相关文献、专利和实际工程应用的基础上,对现有排水抗滑桩结构（抗液化桩、空心排水抗滑桩、箱型排水抗滑桩等）特征及分类进行系统归纳,发现：结构上通常与集排水结构形成“渗-集-排”抗滑组合立体结构系统,主体抗滑形式多为桩型或键型,“渗-集-排”结构通常包括透水孔、辐射状渗水孔和排水花管;通过对典型应用实例的综合分析,指出排水抗滑桩虽已具有显著提高稳定性的优势,但距离其广泛应用和多元化发展还有一定距离。据此提出目前排水抗滑桩研究中施工工艺复杂、力学性能和排水特性不明晰、抗滑稳定性计算理论不完善、平面...     

Incorporating set-up into LRFD method for drilled shafts

The increase of pile resistance with time is referred to as ‘set-up’. This behaviour of driven piles has been widely discussed in many studies by researchers. Meanwhile, there has been little, if any, information regarding this aspect for drilled shafts. Performing a bearing capacity test for a shaft over time, however, requires higher costs and more complicated rigs compared to a driven pile. A database including results from five Osterberg cell-tested drilled shafts conducted at two different stages is considered, from which the set-up effect is statistically analysed. The reliability-based analysis technique using Monte Carlo simulation (MCS) is used to develop separate resistance factors to account for different degrees of uncertainties associated with the predicted reference resistance and the predicted set-up resistance in the framework of the load and resistance factor design (LRFD) method. By incorporating set-up into design, shaft length or number of shafts can be reduced and economical design of drilled shafts can be achieved.     

Limiting equilibrium method for slope/drilled shaft system

The use of drilled shafts to stabilize an unstable slope has been a widely accepted practice. There are two basic design and analysis issues involved: one is to determine the global factor of safety of the drilled shafts stabilized slope and the other one is to determine the design earth thrust on the drilled shafts for structural design of the shafts. In this paper, a limiting equilibrium method of slices based solution for calculating global factor of safety (FS) of a slope with the presence of a row of drilled shafts is developed. The arching mechanisms due to the presence of the drilled shafts on slope were taken into account by a load transfer factor. The method for calculating the net force applied to the drilled shaft from the soil mass was also developed. The interrelationships among the drilled shaft location on the slope, the load transfer factor, and the global FS of the slope/shaft system were derived utilizing the developed numerical closed‐form solution. An illustrative example is presented to elucidate the use of the solution in optimizing the location of the drilled shafts on slope to achieve the desired global factor of safety of the slope/shaft system. Copyright © 2009 John Wiley & Sons, Ltd.     

苍峄铁矿带苍山县沟西西官庄矿区沟西矿段（凤凰山铁矿）主井井筒检查孔水文地质特征分析

苍峄铁矿带苍山县沟西西官庄矿区沟西矿段,又称凤凰山铁矿,为隐伏的鞍山式低品位铁矿,矿区水文地质条件属于中等型。对施工的主井、副井、进风井、东风井和西风井井筒检查孔进行了水文地质编录和分层抽水试验,以主井井筒检查孔为例,划分了4层含水段,求得了各含水层的水文地质参数,对荒径涌水量进行了预测;基本查明了井筒检查孔的含水性等水文地质特征,确定了注浆段,为矿山立井防治水方案提供了设计依据。     

深厚表土层中高强复合井壁结构的试验研究

针对煤矿立井井筒深厚表土层的支护,提出了采用双层钢板高强混凝土复合井壁结构。通过模型试验,得到了这种井壁结构的应力特性和强度特征,通过理论分析和试验结果给出了双层钢板高强混凝土复合井壁承载力的计算公式,从而,为该种井壁结构的实际应用提供了设计依据。其研究成果已在4个井筒中得到了成功地应用。     

Beckenried viaduct: Foundation problems in a creeping slope

Summary The 3150 m long Beckenried viaduct traverses an unstable creeping, slope, the surface of the sound rock lying at depths from 10 to 60 m. Altogether 44 of the total 58 piers of the bridge founded on the sound rock had to be protected by shafts against the creeping soil and loosened rock layers. Based on geological explorations and previous monitoring of the slope displacements the clearance between the rectangular concrete piers and the elliptical shafts was specified to be 1.5 m in the dip direction of the slope and up to ±1.0 m in lateral direction. In order to avoid failure of the shafts due to the unusually large slope movements likely to occur during the service life of the viaduct, an entirely new design concept was applied. It involves flexible shafts consisting of four main parts, namely a rigid shaft collar, articulated ring elements, a rigid trapezoidal cylinder and basal displacement rings resting on the pier footing. Fundamentally, this design permits both: sliding of the shaft as a whole along particular slip surfaces in the loosened rock at depth but also differential displacements due to the creep of the soil strata above it. The sliding at the base contributes to 50% and more to the total surface movements. The shafts also serve as a permanent drainage system for the highly water sensitive slope material. The paper describes the criteria upon which the novel design of the individual shafts were made and also particular constructional details. After a construction period of only four years the bridge opened to traffic in December 1980. Observations made on the completed structure indicate a behaviour of the slope and the shafts which is well in accordance with the predictions.     

Experimental study,numerical modeling of and axial prediction approach to base grouted drilled shafts in cohesionless soils

The pressure grouting of drilled shaft tips has become popular worldwide due to its effectiveness in mobilizing a larger portion of the available tip resistance under service displacements. This paper presents experimental and numerical studies on the load transfer mechanism and factors controlling the axial response of base grouted drilled shafts in cohesionless soils. The study found that the increased axial capacity of grout-tipped drilled shafts under service loads and displacements depended mainly on preloading effects and the increased tip area provided by the grouting process. A simple prediction approach for estimating the tip capacity of grouted shafts utilizing cone penetration resistance was suggested based on the results of the study. The validity of the proposed approach was verified by the analysis of full-scale case studies of grouted shafts reported in the literature.     

Construction of deep tunnel shafts in Mexico city soft clays by the flotation method

The drainage system of Mexico City, one of the largest metropolitan areas in the world, is formed by a large network of interceptors and collectors leading to the main outlet: a 49.3-km-long tunnel with a 6.5 m diameter. To build the access shafts to the tunnels of the system and the deep sumps of the pumping stations in the very soft clays of the lacustrine area of Mexico valley, a technique known as “flotation method” has been commonly used since 1969. The paper presents the main construction steps followed and some aspects of the analysis and design of shafts constructed by this technique. The experience gained obtained after more than 30 shafts have been constructed by this method, and the actual trends in its application are also discussed.     

Analysis of failure of a bridge foundation under rock impact

A bridge pier supported on two drilled shafts collapsed due to the impact by a 130-ton rock in a landslide event. A series of static and dynamic numerical simulations is conducted using a nonlinear finite element analysis program to investigate the bearing behavior and responses of the bridge foundation under rock impact. The rock impact load is evaluated according to the site conditions. The deflection histories at the striking point and the internal forces in the drilled shafts during rock impacts in different directions are analyzed. The bridge pier exhibits significant system effects: the failure of the bridge pier is initiated by the failure of one pier column or one drilled shaft first, followed by the failure of the entire pier. The effects of impact loading direction, striking location, and characteristics of impact load on the behavior of the bridge pier are examined through a parametric study. The capacities of the pier along different loading directions are different due to differences in the group effects of the drilled shafts. The bridge pier is strongest when the impact load is along the 45° direction with respect to the shaft row, and weakest when the impact load is perpendicular to the shaft row.     

Current and future UK practice for the permanent support of shaft excavations

Summary Mining development work in the UK is primarily concerned with the coal industry. Sedimentary rocks of the sandstone, marl and limestone types and coal measures are the predominant strata through which new shafts or existing shaft deepenings penetrate. The paper discusses hydrogeological information, the loadings imposed on shaft linings in such strata and outlines design philosophy. Design formulae are quoted and design practice is reviewed with reference to the current UK Codes of Practice for concrete construction.Included in the overall shaft lining design concept should be a consideration of the installation factors. Construction aspects and the influence of strata water control measures are therefore discussed in relation to recent advances using high-strength concrete and water pressure relief. New concepts in shaft lining design are also proposed and commented upon. Finally, the significant features of shaft lining design and construction are emphasized.