Abstract: The pit collapse occurs in the middle and lower reaches of the Yangtze River.It has extremely risky collapse form.Sometimes the pit collapse can cause the life and the property heavy losses.Therefore,it is necessary to study the pit collapse and the measures of emergency protection.According to the river topographical map of Sanjiangkou before and after pit collapse,this paper has analyzed the cross section changes,and calculated each measured submarine volume.The results show that 80% volume of the pit col...