Experimental Study On Influence Of Vertical Load And Water Immersion On Horizontal Bearing Capacity Of Loess Pile Foundation

With the rapid economic development in the western region and the continual expansion of construction projects,the application of pile foundations in the western loess area has also become increasingly widespread.For the analysis of bearing capacity of pile foundation,the data obtained by the test method is more accurate and reliable.Among them,laboratory model test with small size,easy to operate,can do a variety of conditions,short cycle and other advantages.Therefore,this study discusses the bearing characteristics of pile foundation in loess area through laboratory model test.The existing research on the pile foundation mostly adopts the loading mode of single load.However,in practical engineering,the stress of the pile foundation is often complicated,not only to bear the vertical load transferred from the superstructure,but also to bear the influence of wind,waves such as the role of horizontal load.Based on the above situation,this study summarized the existing research results on the horizontally loaded piles at home and abroad,and explored the variation of the horizontal bearing characteristics of single pile when the single pile of concrete subjected to vertical and horizontal loads at the same time through the laboratory model test and get some valuable conclusions.The main contents and conclusions of the thesis are summarized as follows:(1)The research background of this study and the research status at home and abroad are briefly described.It is found that there are still many deficiencies in the study of horizontal bearing single pile at present,and the research purpose and content of this study are clear.(2)A set of interior model pile foundation loading device is designed and improved by myself.Vertical load and horizontal load can be applied to the model pile at the same time in order to meet the test requirements.(3)Through the laboratory model test,the variation law of horizontal bearing capacity of single pile subjected to pure horizontal loading pile and different vertical loading under soaking and non-soaking conditions was studied.It is known that under the certain load range,the greater the vertical load applied in advance,the higher the horizontal bearing capacity of pile foundation,and the improvement of the bearing capacity of the pile foundation under flooding is smaller than that under the unimmersed condition.When the vertical load acting on the pile top is the same,the horizontal bearing capacity of the pile foundation under water soaking conditions is smaller than that under the unimmersed water condition.(4)The displacement and moment distribution of the pile body under the action of vertical load on the top of the pile are analyzed under the condition of soaking and not soaking.When the flooding conditions are the same,the displacement curves and bending moment curves of pile body are distributed in the same way and decrease along the depth,and with the vertical load increasing,the displacement and bending moment of pile body are more limited.When the flooding conditions are different,it is found through comparative analysis that the lower part of the pile body underwent anti-bending deformation under water soaking conditions,and there was almost no deformation of the lower part of the pile body when it was not submerged.Under the condition of the same vertical load and horizontal load,the displacement of the pile under flooding is larger than that in the unimmersed water.The peak position of the bending moments under immersion is deeper than that under the condition of not flooding.(5)It is analyzed that under the same flooding conditions,in the range of a certain vertical load,when the vertical load of the pile top is larger,the displacement of the pile top and the rotation angle of the pile head are smaller under the same horizontal load.When the water immersion conditions are different,and the pile foundation is subjected to the same vertical and horizontal loads,the pile top displacement and pile head angle under flooding conditions are greater than those under unimmersed water conditions.