超前管棚支护在输水隧洞复杂地层中的应用

Application of Advanced Pipe Shed Support in Complex Stratum of Water Conveyance Tunnel

为保障复杂地层中输水隧洞工程的安全施工,超前管棚支护是一种行之有效的预支护措施。通过对前坪水库上黄线2号隧道、出山店水库北灌溉洞及槐扒黄河提水工程黄李隧洞3个加固工程实例进行分析,结合相关规范给出管棚所采用的钢管管径、钢管环向间距、外插角及钢架间距等超前管棚设计参数的经验值:钢管直径一般在50~180mm之间,支护条件要求较高的Ⅳ、Ⅴ类围岩所采用的钢管直径一般较大(不小于100mm),反之可选择较小管径(一般介于50~100mm);管棚钢管环向间距可在40~80cm的范围内进行选择,一般不大于5倍直径;外插角取值范围因管棚大小而异,小管棚5°~15°,中管棚2°~8°,大管棚1°~3°;钢架间距一般不大于1m,根据现场地质情况可适当加密。从3个工程的施工效果可以看出,超前管棚支护可以有效加强围岩自身稳定、增加围岩承载力、减少变形,达到了在各种特殊地段及复杂地层中输水隧洞安全施工的目标。

In order to ensure the safe construction of water conveyance tunnel in complex formations,advanced pipe shed support is an effective pre-support measure.Through the comparative analysis of three engineering examples of the north irrigation tunnel of the Chushandian Reservoir,No.2 Tunnel of Shanghuang Line of Qianping Reservoir and the Huanghuang River Water Lifting Project Huangli tunnel Reinforcement Project,the steel pipe used in the pipe shed was given in accordance with relevant regulations.The empirical values of the design parameters of the leading pipe shed such as the diameter of the pipe,the circumferential spacing of the steel pipe,the extrapolation angle and the spacing of the steel frame: the diameter of the steel pipe was generally between 50 and 180 mm and the surrounding rock of the IV and V types with high supporting conditions was required.The diameter of the steel pipe used was generally larger (not less than 100 mm),otherwise the smaller pipe diameter (generally 50-100 mm) could be selected;the circumferential spacing of the pipe shed could be selected within the range of 40-80 cm,generally not more than 5d.The range of extrapolation angles was 5°-15° for small tube sheds,2°-8° for middle tube sheds and 1°-3° for large tube sheds;the spacing between steel frames was generally not more than 1 m,which could be properly encrypted according to site geological conditions.The construction effect of the three projects can be seen that the advanced pipe shed support can effectively strengthen the stability of the surrounding rock itself,increase the bearing capacity of the surrounding rock,reduce the deformation,etc.,and achieve the safe construction of the water conveyance tunnel in various special and difficult sections and complex formations.