挖基坑(四面放坡)方形:V=(a+2c+KH)*(b+2c+KH)*H+1/3*K2H3请问1/3*K2H3是怎么来的?1/3*K2H323是平方和立方ab是底宽长,k放坡系数,h为高,c为工作面宽

　　挖基坑(四面放坡)方形:V=(a+2c+KH)*(b+2c+KH)*H+1/3*K2H3请问1/3*K2H3是怎么来的?

　　1/3*K2H323是平方和立方ab是底宽长,k放坡系数,h为高,c为工作面宽