Table 1.

The strata information of Changqingpo Tunnel from DK483 + 978 to DK483 + 907.

Strata sequence	Type	Condition	Thickness/m	Description
< 1–6 >	Filling (Q4ml)	Filling soil	0 ~ 1	Filling soil, mainly with concrete
< 2–11 >	Clay (Q4ca)	The distribution of soft and hard soil is irregular, mainly in hard plastic state, and partially in soft plastic state	0 ~ 43	The filling material of karst cave is mainly clay soil, which is gray black, yellow relatively uniform soil, and a small amount of local embedded gravel breccia
< 2–11–1 >	Broken stone	It is mainly filled with block stones	0 ~ 3	Karst cave filling material is mainly lump stone, which is gray white, and lump stone is locally distributed in clay of < 2–11 >
< 16–1 >	Limestone (C3m)	The joints are well developed, the dissolution erosion is serious, and the local erosion is very serious	0 ~ 16	The color of limestone is ashy, gray, which has thick layer massive structure and cryptocrystalline structure. It is the integrated contact with Weining Group below