Preliminary Research On Lateral Seisimic Behavior Of Batter Piles Based On Shaking Table Test

Now,in civil engineering,pile foundation has become one of the most common forms of deep foundation.It is widely applied to the bridge engineering both of sea and river,port engineering,oil and electric transportation line and offshore oil production platform.For in these engineering,the building usually threatened by the lateral load such as collision,tide and earthquake,the battered pile is often applied.Besides,the battered pile is easier to be destroyed during the earthquake than straight pile sometimes and both at home and abroad,it has always been a hot topic of concern that the seismic behavior of battered pile in liquefied soil.Based on the comparison of the shaking table test of the symmetrical double straight pile and the symmetrical double batter pile,the lateral seismic behavior of the batter pile in the liquefied soil is studied.First of all,design scheme for shaking table test.In this paper,the design and research of the electromagnetic vibration table structure and related parameters,data acquisition system,model box,model soil,model pile,sensor arrangement,test conditions and other aspects are carried out.Select the shear box as model box,model pile and pile cap has two groups including a group of symmetric double straight piles and a group of symmetrical double battered pile.The pile foundation is designed as an end bearing pile type,and the bottom of the pile body is embedded in the rubber bearing layer of the bottom of the model box.Model soil is standard sand from Fujian,including non-liquefied dry sand and saturated sand.In the soil,the acceleration sensor and the whole pressure sensor are arranged evenly.The FBG strain acquisition system is attached to the pile body,and the acceleration and displacement sensors are arranged on the pile cap and platform.The sine wave which the peak value of acceleration are 0.15 g,0.20 g,0.30 g and the EL-Centro wave and Kobe wave which the peak value of acceleration are 0.20 g are selected to input respectively in the test.Secondly,MATLAB software is used to process the data collected in the test.In this paper,the relative table top acceleration and displacement amplification factor of the symmetrical double straight pile caps and the symmetrical double batter pile caps of the dry sand and saturated sand are compared and analyzed.At the same time,the development and variation law of pore water pressure in saturated sandy soil is presented and then study the battered piles lateral dynamic response characteristics on the condition of liquefaction.The study shows that the lateral dynamic response of the battered pile is lower than that of the straight pile whenever in the dry sand and saturated sand.So the ability of the battered pile to resist the horizontal load is better than that of the straight pile.Finally,according to drawing the bending moment envelope diagram of pile and comparing them,it can be concluded that under the regular sine wave inputting,the bending moment distribution of the straight pile and the battered pile is symmetrical,and the maximum bending moment is mostly in the top of the pile.In the saturated sand,the interaction of the pile and soil decreases because of the liquefaction.The bending moment of both the straight pile and battered pile are enlarged which the straight pile is about 7 times than before and the battered pile is more than 20 times than before.Additional bend moment of the battered pile is significantly greater than that of the straight pile.What is more,it is showed the same rules in irregular seismic inputting.After the liquefaction,the same strength of the batter pile foundation is more likely to occur bending failure than the straight pile foundation.According to the position of the maximum value of the pile bending moment,the weakness of the batter pile foundation is analyzed,which provides the theoretical basis for the seismic design method of the batter pile foundation in the liquefied site.