十分火急，速度

Rollers or other compaction devices increase soil density by expelling air from the voids in the soil and by rearranging or forcing the soil grains into more intimate contact. water aids as a lubricant up to the optimum moisture content .in porous soils air is easily forced out ,but the heavy tight ,cohesive materials much effort is required .because of this ,heavy cohesive materials must be placed in thin layers if the air is to be expelled readily.
Compactors include tamping or sheepsfoot rollers ; pneumatic-tired rollers ; smooth steel-wheeled rollers ;segmented plate compactor ;grid rollers ,vibratory compactors in the form of vibrating pads ,steel wheels or Pneumatic tires and finally the hauling and spreading equipment itself ,in some instances tow types of compactors ,such as smooth steel wheel and pneumatic tires are combined in a single unit ,with most compactor types ,units are available in several weights or provision is made to change the weight readily .there is a sm

十分火急！~~~~ 十分火急 十分火急呀，电脑高手！！ 十分火急的问题!!! 十分火急请求帮助 十分]火急``案例分析 . 十分火急数学应用题 十分火急英语题 十分火急英语翻译 十分火急语文题