Anti- Liquefaction Characteristics Research On The Composite Pile

As a relatively new form of pile, composite pile integrates the advantages of soil-cement and reinforced concrete, utilize the reinforced concrete core pile to bear the main vertical load, and provide high side friction with the large contact area of the lateral soil-cement mixing pile and soil mass, featuring the advantages of convenient construction and high bearing capacity. Thus, it can be widely applied in Yellow River flood area.Although some scholars have conducted the experimental study concerning the earthquake liquefaction characteristics of saturated silt in Yellow River flood area, however, for the way how to improve the liquefaction resistance of foundation for the region, especially the measures to reduce the liquefaction effect on pile foundations, the in-depth discussion has been made. Traditional measures of improving the conditions of foundation liquefaction processing still have their own limitations. The composite pile makes full use of the advantages of soil-cement and reinforced concrete, and its technical advantages are obvious. However, there are no relevant research literature s for the liquefaction resistance study of composite pile under strong earthquake, and it can be seen that the theoretical research lags behind the practical engineering application.In this paper, the liquefaction resistance of composite piles under earthquake action is analyzed by using finite difference analysis software Flac3 d. The liquefaction resistances of single pile and pile group of composite pile under different conditions are respectively discussed, the general rules affecting the foundation soil pore water pressure and the time interval changes of excess pore pressure ratio are summarized, and the analytic algorithm of composite pile foundation pore water pressure is preliminarily discussed. The conclusions are as follows.1. The composite piles have changed the pore water pressure distribution of foundation soil under earthquake action, and cluster area of pore water pressure appears near the pile tip.2. In the horizontal direction, with the increase of distance from the pile core, the vibration of pore water pressure is not obvious. The monitoring point which is farthest from the position of pile core rapidly reaches to the peak under the action of earthquake, maintains relatively stable, and the liquefied state appears when judging the local moment from the excess pore pressure ratio.3. The changes of the scope of soil-cement affect the position of the pore water pressure concentration area, make it offset to the direction away from the pile core, near the pile, the pore water pressure and time interval of excess pore pressure ratio change obviously, namely the dissipation effect of pore water pressure is relatively good.4. The changes of water level influence the distribution of pore water pressure and increase the dissipation path of pore water pressure. However, the effect is limited.5. The liquefaction resistance effects of composite piles and group piles are more obvious, the increase of pile spacing makes the pore water pressure concentration area offsets to the borders, the max. value of pore water pressure in the area is reduced, and the increase of single pile spacing extends the scope of liquefaction resistance of pile groups.6. Analytical solution algorithm of boundary and the definite condition of composite pile’s pore water pressure has been carried on the preliminary discussion in this paper. The calculation result of pore water pressure on one-dimensional case tallies with the simulation situation.