In order to explore the karst development characteristics and the thickness of karst roof in the eastern section of the bridge belt, the water types and recharge rules of karst fissures were summarized, and a karst classification model considering the grouting amount and filling situation was established. Statistical analysis and K-means cluster analysis were used to study the karst law in the study area. The results showed that 44.44% of the karst caves had serious water leakage, 18.52% had slight water leakage~water leakage, 37.04% had no water leakage, 36.54% of the karst cave fillers were in the soft plastic state, 26.92% were in the flow plastic ~ soft plastic state, 19.23% were in the plastic state, and 17.31% were in the other states. The grouting amount was negatively correlated with the state coefficient, and positively correlated with the height of the karst cave and the thickness of the roof, and the height of the karst cave had the greatest influence on the grouting amount. The logarithmic value of the high value of a karst cave is less than that of a karst cave and the number of karst caves, and the measured value of the probability of a certain roof thickness and the thickness of the roof satisfy the cubic function relationship. 12.16% of the caves were unfilled, 9.46% were semi-filled, and 78.38% were fully filled. The cave rate was 25.52%, the average karst rate was 7.69%, the average cave height was 2.87m, 1/3 of the cave height was less than 1.4m, 1/2 of the cave height was less than 2.2m, and 90% of the cave height was less than 5.5m. In the Ca-type water body, the main source of karst fissure water is pore water. The K-means clustering algorithm was used to evaluate and classify the karst caves, and the karst caves were divided into two categories, the average value of the first type of grouting was 24.50m3, the average state coefficient of the filling was 0.38, and the average height of the karst cave was 2.32m, and the average value of the second type of grouting was 2.36m3, the average state coefficient of the filling was 0.57, the average height of the karst cave was 5.98m, and the contour coefficient was 0.84.