poorly graded gravel meaning in English

劣级配砾石

2 identify the soil as a poorly graded gravel , gp , or as a poorly graded , sand , sp , if it consists predominantly of one size ( uniformly graded ) , or it has a wide range of sizes with some intermediate sizes obviously missing ( gap or skip graded )
2如果土包含一个主要的粒径(均匀的级配) ,或者有一个很宽的,一些中间粒径明显缺失的范围(间隙或跳跃的级配)