looseness of structure造句

• Gravel layer is a usual complex instable formation in drilling engineering . there are some basic features such as looseness of structure , increment , unequal sized grain . it is commonly to form discrete single - grained structure
  在三个计算式的基础上采用visualbasic编制了潜孔锤同心跟管钻进风量、风压计算及空压机选型程序。