成昆铁路昔格达地层工程地质特性及对策研究

Research on the Engineering Geological Characteristics and Engineering Countermeasures of Xigeda Strata of Chengdu-Kunming Railway

研究目的:成昆铁路是四川、西北地区与云南省及东南亚地区的重要连接通道,沿线昔格达地层分布较广,但受其成因机制、物理力学特性、构造条件及地下水等因素的影响,在工程上主要表现为边坡失稳破坏及隧道围岩大变形等工程问题,给工程建设带来巨大危害。本文结合成昆铁路扩能改造工程建设,在前人研究的基础上,针对穿越昔格达地层铁路修建的关键技术问题,通过试验分析,提出其合理的地质参数和工程措施,从而解决实际工程问题。研究结论:(1)昔格达地层为极软岩,产状平缓,具有水稳性差、透水性弱的特性;(2)针对路基工程,昔格达地层路堑边坡当岩层倾角≥5°时应考虑顺层影响,高填方及斜坡填方段应设侧向约束桩,加强地表排水及坡面防护,防止基底受水软化;(3)针对桥梁工程,昔格达地层宜作为明挖基础和桩基础的持力层,但基坑开挖后应尽快浇筑混凝土,以免坑壁坑底渗水软化变形;(4)针对隧道工程,昔格达地层应遵守"短进尺、重超前、少扰动、严控水、强支护、快封闭、早衬砌"的极软岩隧道施工原则;(5)本研究成果对我国西南山区类似工程地质条件下的铁路、公路等工程建设具有借鉴意义。

Research purposes： The Chengdu - Kunming railway is the important connection channel for the regions of Siehuan, the northwest China and Yunnan province and Southeast Asia, and along the railway the Xigeda strata are widely distributed. However, affected by its formation mechanism, physical and mechanical properties, structural conditions and groundwater, special engineering problems of the slope and the deformation of surrounding rock existed, and brought great harm to the engineering construction. Based on the capaeity expansion project of Chengdu - Kunming railway, for the key technical problems of the Xigeda strata of the railway construction, this paper was on a certain basis of the summary of existing results and experience, and experimental study, the reasonable geological parameters and engineering measures were put forward to solve practical engineering problems. Research conclusions ： （ 1 ） The Xigeda strata is extremely soft rock, the dip angles of rock formation is gentle, and with the characteristics of poor stability of water and weak permeability. （2） For the subgrade engineering, the Xigeda strata cutting slope should consider the bedding influence when the dip angle is equal to or greater than 5 degrees; the high fill and slope fill sections should set the lateral restraint piles; strengthening surface drainage and slope protection to prevent the substrate from water softening. （3） For the bridge engineering, the Xigeda strata should be bearing layer as the openexcavation foundation and pile foundation, however, as soon as possible after the excavation of concrete to avoid the pit wall and pit bottom seepage softening deformation. （4） For the tunnel engineering, the Xigeda strata should abide by the principle of soft rock tunnel construction of ＂the short footage, attach importance to advance forecast, reduce disturb- ance, strict control of water, strengthening support, rapid sealing, timely lining＂. （5） The results of this paper can be used for reference in the construction of railway and highway under the similar engineering geological conditions in the southwest mountain area of China.