A number of thin cracks appeared in the wall.

墙上出现了许多细裂缝。

《牛津词典》

When that wall cracks, there's another underneath.

等那层墙壁裂开之后，下面还会有一层墙。

youdao

Wall cracks occur commonly in buildings of mixed structures in our country, and the main reason is the material contraction due to temperature variation.

目前国内的混合结构建筑，由于温度变化以及材料伸缩等原因引起的墙体裂缝现象较为普遍。

youdao

"Most of the ones I looked at had just cracks in the wall--of no structural significance, " he says.

CNN: ASIANOW - TIME Asia | Taiwan: The Day the Earth Moved--Page 3

Using state-of-the-art surveying equipment, Reeves is expected to begin searching cracks on the northern wall for a secret doorway leading to a previously undiscovered space.

CNN: Search for Nefertiti's burial site given green light

Deep cracks beneath the waterline led to parts of the 80-year-old harbour wall collapsing in 2012.

BBC: Weymouth harbour wall: Warning over repair noise