Building safety data (建筑安全资料) , the direct factors causing the construction safety accidents are unsafe behavior, unsafn: after the excavation of the soil in the natural state, the structural connection is destroyed, and the volume of the structure is increased because of the loosening. After the backfill compaction, the volume of the original volume can not be restored. The porosity is expressed as a coefficient of relaxation, including the initial coefficient of relaxation and the final coefficient of relaxation. The initial porosity was applied to the loose volume after the soil was excavated, and finally the looseness was used for volume calculation after backfill compaction. prefabricated parts in the construction site layout, what are the requirements of the layout of the component? Answer: 1, easy to lift, stacked production 2, keep good driving route, choose crane model 3, convenient component construction, 4 hanging points at the same level. what is the new Austrian law? What is the difference between it and the traditional mining method? Answer: the new Austrian method is applied to the theory of rock mechanics, maintenance and use of the self bearing capacity of surrounding rock as the base, with anchor and injection as the main supporting concrete means to support timely, control of surrounding rock deformation and relaxation, the rock became part of the suppo