Design Theory And Construction Technical Study Of The Chemical Churing Pile Composite Foundation And Its Application

Jet grouting is a foundation treatment method that a high-velocity grout, which is forced under high pressure out of a nozzle, cuts into the soil to form a cylindrical soil-cement solidification, and with the result of that the bearing capacity of the foundation is enhanced and the settlement and the differential settlement are reduced. This process is widely used in constructional engineering, highway bridge, coal mine and railway bed. However, duo to the complexities of the geological condition and the mechanical properties of the foundation, researches for this composite foundation are still in the initial stage, its bearing mechanism and design theory are still remained to be discussed. Linking with the research called " Design Theory and Construction Technical Study of the Chemical Churning Pile Composite Foundation and Its Project Application" in Guilin, Guangxi province, the bearing properties of the chemical churning pile and its vertical bearing capacity calculation are fully discussed through the theoretical and practical analysis.Firstly, the basic concepts of the composite foundation and the main characteristics of the chemical churning pile composite foundation are introduced in some detail. After that, configuration of the spray, structure of the injection stream, hardening mechanism of the jet grouting are probed. Then the pile-soil stress characteristics and stabilizing mechanism of the composite foundation are fully discussed. Based on the close analysis of the influence factors of the vertical bearing capacity, circular aperture extension theory is employed to establish the computing formulas for the pile vertical stress and the foundation vertical bearing capacity, respectively. Moreover, with analyzing the features of the calculation parameters such as materials of gunite mortar, jet pressure, diameter of the jet pipe, pile length, pile layout, a design theory for chemical churning pile composite foundation is proposed. Then, the variation of the pipe deformation with loads, the deformation coordination of pile and soil are studied. And methods to decide pile-soil stress ratio and the compressive modulus are developed. Meanwhile, the corresponding design method and the design parameters are proposed. In addition, studies for construction technique and quality detection of the chemical churning pile composite foundation are presented. Finally, taking the actual project "Economics and Trade Square" in Guilin as an example, the results show that the field tests are well-tried.