Detecting The Subgrade Compaction By The Direct Wave Method

At present, with the rapidly development of our national economy, the road construction of inland has reached the state of unprecedented prosperous. However, the existing methods of detecting compaction are waste time and laborious or don't have enough precision. So we bring forward the method of direct wave. This method mainly establish a kind of experience equation with the correlation between the shear wave velocity of. soil and it's dry density. In application , if only we substitute the velocity of shear wave into this equation, we get the dry density of soil. Then, we can easily work out its compaction.By dissertating the theory foundation of reconnaissance with wave and the compact theory of soil, this paper analyses the factors which influence the transmission velocity of shear wave, and boil them down to the categories and the dry density of soil. This paper also tables some proposals to improve the compaction standards of our countrie.With The direct wave method we only can work out the dry density of the topsoil of subgrade. In order to demonstrate that the dry density of the topsoil of subgrade can represent that of the whole layer of soil, this article analyses the subgrade stress field. During the process of analysis, according to the circumstance of actual experiment data, we considered two kinds of circumstances: the smooth drum roller rolling and the vibration roller. Finally, we drew the conclusion that the compaction of the topsoil of subgrade can represent that of the whole layer.The contrary experiment between the dry density of soil and the velocity of direct shear wave was carried through. With the data we got, we made programmes of the matlab language of four kind of frequently used curve model. According to the correlation coefficient we got, the appropriate curve model are ρ=0.2025V~0.3699,ρ=0.7660+0.0020V,ρ=1.3288e~0.0009v. We verified them with the method of vibration three time and press three times. The errors are admissible.