Experimental Study On P-y Curves Of Laterally Loaded Pile Which Is Embedded In Expansive Soil

With the rapid growth of the national economy, it lead to the infrastructure construction field expands unceasingly. Consequently, laterally loaded pile will be used increasingly in the expansive soil subgrade. Undoubtedly, for the analysis of laterally larger loaded pile foundation, by using of the p-y curve method has great superiority. But for different soil conditions, the p-y curves have great difference. Moreover, the research on p-y curves at home and abroad, in the general only for normal soil conditions, but for other special soils, such as expansive soils, related study on p-y curves are rare in the about literature. Therefore, the experimental study on p-y curves of expansive soils, is the premise to analyse laterally loaded pile in this expansive soil, and it has important theoretical value and practical significance.Based on existed research at home and abroad, the experimental study on p-y curves of laterally loaded pile in expansive soils is carried out in this thesis. The study is funded by the following research projects. The project supported by National Natural Science Foundation,"The study on nonlinear rheological properties of expansive soil"(No.,50978097), and the project supported by National Natural Science Foundation,"The experimental study on interaction of pile-soil in expansive soil"(No.,50378097). Through a series of model tests, the variety laws of p-y curves of laterally loaded pile which is embedded in waterlogged expansive soil or un-waterlogged expansive soil are have been explored respectively, and the related theories are established. The main work contents and the innovative achievements of this research are as follows.The main work contents of this research1. Based on reviewing the research literatures related on laterally loaded pile at home and abroad, the model test research plans of laterally loaded pile in expansive soils have been designed.2. Through a series of model load tests for laterally loaded pile in waterlogged expansive soil and un-waterlogged expansive soil, the relationship between pile side soil resistances and pile shaft displacements have been explored respectively.3. By the static load tests on model piles, the characteristics and the laws of p-y curves of laterally loaded piles in expansive soils have been studied.4. According to the triaxial compression tests, the parameters of p-y curves of waterlogged expansive soil or un-waterlogged expansive soil have been researched and determined.5. On the basis of experimental research, the theoretical p-y curves of laterally loaded piles in expansive soils have been studied, and the related theoretical models are established.The main innovative achievements of this research1. Through experimental research, it is discovered that the tested p-y curves of un-waterlogged expansive soils have the strain hardening characteristics just as the hard clay soils. Under any depth, the p-y curve is all distributed according to a power function form. The deeper the soil layer is, the greater the exponent of the power function of p-y curve is. On the contrary, The shallower the soil layer is, the smaller the exponent of the power function of p-y curve is.2. After expansive soil is soaked, its p-y curves have obvious strain softening characteristics. When expansive soil is fully soaked, its p-y curves are distributed according to a hyperbola function form. In the deeper soil layer, the expansive soil is not all soaked, its p-y curve is distributed according to a transition form, which is transformed from hyperbola function to power function.3. Research shows that, after expansive soil is soaked it is changed to soft. When the soil is soaked, the horizontal limit bearing capacity of pile is much smaller than when the soil is unsoaked.4. Through a comparative study on the p-y curves under the two conditions of expansive soil is soaked and it is unsoaked, it is found that, if using the p-y curves of un-waterlogged expansive soil to design pile foundations which are embedded in expansive soil and of which is below the groundwater level are not safe.5. Through a comparative study on the p-y curves in expansive soil and in soft clay, it is found that, the p-y curves of soft clay should not be used for pile foundation design in expansive soil.6. Based on the soft clay’s p-y curve equation which is recommended by "The code for pile foundation of Harbour Engineering", a power function equation of the p-y curve of un-waterlogged expansive soil is established, and the related parameters are obtained too.7. On the basis of experimental research, for waterlogged expansive soil, two kinds of p-y curve equations are established respectively, which are in the form of power function and in the form of hyperbola function. At the same time, the related parameters are obtained too.The above research provides an important theoretical basis for the calculation and the analysis of laterally loaded piles in expansive soil. Similarly, for the study of laterally loaded piles in other special soft soil, it also has an important reference value.