Abstract：Abstract ： Research purposes ： The Chengdu - Kunming railway is the important connection channel for the regions of Sichuan，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 capacity expansion project of Chengdu - Kunming railway，for tlie key technical problems of tlie Xigeda strata of tlie 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 tiie bridge engineering，the Xigeda strata should be bearing layer as the open excavation 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.
2017, Vol. 34 
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