Characteristics and Causes of Cracking of Sanxingdui Moon Bay City Wall

The Moon Bay City Wall of Sanxingdui is built of pale yellow sand and yellowish brown clay. The yellowish brown layers are suffering severe cracking and spalling. Hence, this paper conducts a specific investigation and performs evaporation and drying–wetting cycle tests on five rectangular specimens with different aspect ratios. The results show that the damage ratio first increases to 50.7% and then declines as the height of the layers rises. The average water content of the layers decreases from 21.8% to 12.8% by increasing the height of the layers. The pattern of the primary crack networks is related to the aspect ratio of the soil blocks. In fact, when the aspect ratio of the blocks is always greater than six, the main crack network has a parallel pattern. When the aspect ratio of the blocks is either greater than six or less than one-sixth, a laddering pattern is possibly created. When the aspect ratio of the blocks equals one, the cracks probably form a polygonal pattern. Moreover, under drying–wetting cycle conditions, the number of the main cracks is basically stable, but the average crack opening increases. A large number of tiny cracks are also formed and propagated rapidly, which further leads to spalling of the soil layers.