预应力高强度混凝土管桩在溶洞场地内的应用

预应力高强度混凝土管桩(PHC)具有桩身强度高、耐打性好、穿透力强以及施工效率快等特点,因此在溶洞场地施工中广泛应用。本文笔者将结合具体的溶洞场地建筑施工实例,简要探讨预应力高强度混凝土管桩的具体施工过程,希望能对类似工程起到借鉴作用。     

Preliminary engineering application of microseismic monitoring technique to rockburst prediction in tunneling of Jinping Ⅱ project

Monitoring and prediction of rockburst remain to be worldwide challenges in geotechnical engineering.In hydropower,transportation and other engineering fields in China,more deep,long and large tunnels have been under construction in recent years and underground caverns are more evidently featured by ＂long,large,deep and in group＂,which bring in many problems associated with rock mechanics problems at great depth,especially rockburst.Rockbursts lead to damages to not only underground structures and equipments but also personnel safety.It has been a major technical bottleneck in future deep underground engineering in China.In this paper,compared with earthquake prediction,the feasibility in principle of monitoring and prediction of rockbursts is discussed,considering the source zones,development cycle and scale.The authors think the feasibility of rockburst prediction can be understood in three aspects：（1） the heterogeneity of rock is the main reason for the existence of rockburst precursors;（2） deformation localization is the intrinsic cause of rockburst;and（3） the interaction between target rock mass and its surrounding rock mass is the external cause of rockburst.As an engineering practice,the application of microseismic monitoring techniques during tunnel construction of Jinping II Hydropower Station was reported.It is found that precursory microcracking exists prior to most rockbursts,which could be captured by the microseismic monitoring system.The stress concentration is evident near structural discontinuities（such as faults or joints）,which shall be the focus of rockburst monitoring.It is concluded that,by integrating the microseismic monitoring and the rock failure process simulation,the feasibility of rockburst prediction is expected to be enhanced.     

科技助力余家隧道攻艰

渝（重庆）利（川）铁路余家隧道被列为渝利铁路五大高风险隧道之一和重点控制工程。余家隧道全长3491m,集暗河、溶洞、溶泥、瓦斯为一体,溶洞最大埋深约369m,地质条件复杂,科技含量高,施工难度大,被专家誉为“地质迷宫”,为中国铁路隧道建设史上所罕见。     

龙岩某冲孔灌注桩基础事故的处理与分析

本文以龙岩市商会大厦桩基工程施工为背景,通过对某桩基事故的处理与分析,介绍了冲孔灌注桩工艺在溶洞、裂隙发育地区施工过程中,由于地质情况复杂或者施工控制不当等情形下造成的问题所采用施工处理措施。     

嵌岩桩在岩溶地区的工程应用

结合工程实例对嵌岩桩的设计、施工及工程问题进行分析研究,指出嵌岩桩具有单桩承载力高、沉降小、抗震性能好、群桩效应小等优点,实践证明该桩可在铁路桥梁工程中被广泛使用。     

复合载体夯扩桩处理软弱及溶洞地基

介绍了复合载体夯扩桩施工工艺及施工要点,利用复合载体夯扩桩的优点,提出了处理软弱及溶洞地基的方法,经工程实践检验,该方法是一种处理软弱及溶洞地基的经济、有效、施工方便的方法,能为其他类似工程提供参考。     

溶洞地区桩基的设计及施工

论述了特殊地质条件溶洞地区基础的设计,较详细阐述了桩基的选用原则,以及溶洞地区桩基的施工注意事项,解决了桩基施工中存在的问题,从而保证桩基施工质量。     

特殊地质隧道的施工技术

以忻阜高速公路火焰山隧道为例,介绍隧道围岩变化频繁且伴有溶洞出现的地质条件下安全、高效的施工技术,重点介绍溶洞的处理方法,为类似地质条件的隧道设计施工积累经验。     

隧道顶部溶洞对围岩稳定性影响的数值分析

以在建的某高速公路岩溶隧道为工程背景,采用有限单元法,运用迈达斯GTS分析软件,建立隧道结构及围岩的三维分析模型,重点分析了不同位置、大小的顶部溶洞在开挖过程中对围岩变形位移、力学特性、塑性区以及支护结构受力的影响,研究了顶部溶洞对隧道围岩稳定性的影响,所得结论可为岩溶地区隧道工程的设计、施工和研究提供指导。     

膏状浆液灌浆在构皮滩水电站溶洞处理中的应用

膏状浆液灌浆是通过在水泥浆液中添加增塑剂、速凝剂等复合材料,使浆液具有很好的可控制性和抗水冲性能,是尤其适合于大孔隙和有地下水流地层灌浆的一种方法。文章介绍了构皮滩水电站左岸溶洞段灌浆采用膏状浆液进行封闭处理的情况,阐述了膏状浆液在本次施工中的材料选用、配合比试验、浆液制备技术及灌注效果。施工达到了预期目的。