Inclined Earth Retaining Structure Method(from hereafter will be referred to as IER is an temporary structure wherein the soldier piles(hereafter will be referred to as front support) and stabilizing pile(hereafter will be referred to as back support) are installed at an angle and integrated into a single structure. The installation of the back support effective distributes the earthpressure acting on the front support thereby increasing the structural stability of the temporary.
By installing the back support at an inclined position, the frictional resistance generated by the movement of the .front support or by the soil and the back support during toppling produces the effect of an earth anchor. This has the advantage of obtaining structural stability by rigidly connecting the front and back support.
Even though numerous mechanical advantages can be obtained from the installation back support in IER Method, there complicated mechanism are formed due the back support installation angle, installation interval and other installation factors. Therefore there is a need to verify the actual effects and to analyze the mechanism. Using this as the basis, an analytical method must be developed to compute the earthpressure acting on the front and rear support, and structural stability.
In this study, laboratory model test was used to determine the mechanism and establish a method of analytical method for the IER Method. Laboratory model test with different forms and types of front and back support were performed. Laboratory model test on sand and clays was also performed to analyze the mechanical behaviour in different soil conditions.
It was determined from the laboratory model test performed in sand that the lateral displacement reduction due to stiffness was 5.3%, pullout resistance was 28.9% and earthpressure reduction was 65.8%. The results show that the back support possesses the stabilizing effect of both the earth anchor and a stabilizing pile.
In the laboratory model test in clay wherein the test was performed with a free and fixed lower end condition for the front and back support, it was determined that the largest lateral displacement reduction effect was obtained from the test with both ends fixed followed by back support fixed, front support fixed and both ends free.
Furthermore the analytical method for IER Method using Soil Wedge Theory was recommended. Based on the analysis of the laboratory model test in sand, it was determined that the back support has an influence width of 5.21 times the pile width. Therefore, if we can determine the actual influence width of the back support in different soil conditions through field monitoring then we can accurately compute the active earthpressure acting on each member and develop and accurate design method.