甘肃引洮供水工程饱和黄土隧洞施工方法选择的工程地质研究

甘肃引洮供水一期工程总干渠13#、14#、15#隧洞围岩为al-lQ2饱和黄土,地下水位高于洞顶4³7m,饱和度一般在98%¹00%,水稳性很差。因此,该段隧洞施工方法的选择十分重要,从工程地质角度研究其工程特性,采用D rucker-Prager弹塑性模型、关联流动法则,模拟了传统钻爆法开挖时隧洞稳定性,计算表明,若采用钻爆法,由于围岩的岩性软弱,隧洞开挖后,在隧洞周围较大范围内存在应力降低区,隧洞位移十分迅速而且位移量非常大,洞顶下降发生塌方并引起地面沉降。从盾构法施工对地质条件的适应性分析,其施工风险相对较小,施工过程中可利用护盾很快封闭围岩,因此该段隧洞宜采用盾构法施工。

INVESTIGATION OF ENGINEERING GEOLOGY IN SATURATED LOESS FOR SELECTION OF TUNNEL CONSTRUCTION METHODS IN YINTAO WATER SUPPLY PROJECT,GANSU PROVINCE

The 13^th,14^th and 15th tunnels on general main canal of the First-phase Engineering of Gansu Yintao Water Supply Project go through saturated loess stratum in al-lQ2.Underground water level is about 4 to 37 meters higher than the tunnel crest.The saturated degree of loess is generally 98～100℅.The saturated loess stability is poor.Choosing the method of the construction in the tunnel is very important.it’s the engineering characteristics are examined using engineering geology methods.The Drucker-Prager elastic-plastic model and associated flow rule are adopted.The stability of the traditional drilling and blasting method is assessed for the tunnel.It is found that the drilling and blasting method,can cause the large lower stress area in the tunnel surroundings.The displacement of the tunnel is quickly developed and very large.Consequently,the tunnel crest can fall and collapse.It can results in sinking in the ground.The paper further analyzes the adaptability of the shield tunneling method.This construction method has lower risk.It quickly closes to round the rock using the shield in the construction process.Therefore, it is suggested that this tunnel choose the shield tunneling method.