南昆线路基岩溶注浆整治试验研究

ON FIELD GROUTING TEST REMEDYING FOR KARST COLLAPSE AREA IN SUBGRADE SECTION ALONGSIDE NANNING-KUNMING RAILWAY

南昆线通过碳酸岩地段的路基长约300公里,为消除隐伏岩溶隐患,确保铁路运输安全,我们在开展大规模注浆整治施工之前,选择具有代表性的岩溶异常工点5处进行注浆加固施工试验。以便进一步研究注浆加固机理和施工工艺,优化设计参数,降低施工成本。通过注浆前后注水试验和物探对比检测以及检查孔取芯检查表明:注浆加固岩溶异常,其浆液充填率可达70～80％,基本上达到堵塞松散物质搬运通道的目的;同时地层强度,特别是洞隙中充填的松散物的强度得到提高,抗塌陷能力亦得到提高;注浆前后,地层渗透性差异较大,注浆加固后,地层的透水性降低1～2个数量级,在相当程度上起到了封闭表水的作用。 试验结果还表明:注浆扩散半径与地质条件和注浆压力有关,一般情况下2～7米,注浆孔距平均以5米左右为宜;注浆结束压力,当胶球止浆段为岩层时以0.3～0.4MPa为宜,不小于0.3MPa当为土层时以0.1～0.2MPa为宜,不小于0.1MPa。注浆加固深度,对于浅层溶洞以10米左右为宜;对于溶蚀破碎带,以基岩面下5米左右为宜,并着重加固基岩面附近。

Nanning-Kunming railway, subgrade of line passes through area being rich of car- bonate rocks accounts for about 300 km. To eliminate the hidden disasters of covered karst, to ensure safety of rail transportion, and to research on the mechanism and operational technology of the grouting remediation, to optimize design parameters, to reduce construction costs, the five subgrade sections of typical karst phenomena are selected and tested for grouting treatment prior to construction in large scale. Injection tests and geophysical prospecting tests being performed anterior /posterior the grouting,and the random sampling results by drilling hole in grouted area show that the voids filling capacity with cement slurry is about 70-80% and passageway for loose soil grain is essentailly blocked up and the strength of the strata,especially, the strength of loose soil mass is increased, and the roof soil capacity against collapse is also raised at the same time. Differences in water absorbances of strata anterior /posterior the grouting is very large ,the water absorbance of strata grouted is decreased to 1~2 orders of magnitude, the seepage ?proof surface sealment is also plained to a large extent. The experimental results show that the effective radius of grouting is related to geological conditions and grouting pressure is ordinarily 2~7 m, 5m acting as the average distance of grouting hole is suitable. The pressure,0. 3-0.4MPa, required ending grout is suitable for rock strata that the rubble ball for blocking cement slurry located in,not less than 0. 3MPa, 0.1~0.2MPa for soil strata,not less than 0. IMPa. For the depth of grout strengthening. 10m or so is suitable for karst cavities covered at shollows, 5m or so for karst dissolution zone. The bedrock surface grouting is of much importance to block karst cavities and make the soil mass above bedrock surface a crust to protect against collapse.