Development Features and Treatment of Karsts along No.1 Gaoping Tunnel on Yi-Wan Railway

No.1 Gaoping tunnel on Yi-Wan railway passes through T~2_(1j) limestone.The tunnel is located in vertical-circulating karst zones,with the maximum overburden being 104 m.The karsts along the tunnel are extremely developed,with a total of 51 karst caves having been discovered during the construction of the tunnel.By means of analysis on the karst caves discovered during the tunnel construction,the article makes a study on the features of the development of the karsts located in vertical-circulating zones.On basis of the features of the development of the karsts and the characteristics of the engineering structures,the article suggests a karst scale determination standard,recommends some karst treatment measrues and makes an assessment on the effect of the karst treatment.