It was confirmed that when the ground at the back of the L-type retaining wall was improved using cement, the value of horizontal earth pressure became almost zero after the improved part of the ground hardened a few days later (2009). It was also revealed that when overburden load was place on the back of the retaining wall, no horizontal pressure was created since the retaining wall and the improved part of the ground were integrated into a whole. Furthermore, it was confirmed that the larger was the ground improvement range (θ), the larger were the stability moment at the time of overburden loading and the friction resistance at the underside of the batholith, making retaining wall displacement smaller.
From the aforementioned studies, ample knowledge about the ground improvement effect at the back of the retaining wall was gained. On the other hand, however, it is practically impossible to discuss the ground improvement effect in detail because earth pressure acting on the ground improvement boundary surface was not measured and because there was only one type of overburden loading position.
Due to the aforementioned reasons, in this study, various experiments are to be conducted by creating a device which made it possible to measure earth pressure acting on the ground improvement boundary surface and using the ground improvement shape and the loading position as the parameters, and the relationship between the ground improvement shape ad the ground improvement effect is to be examined.
The key results obtained from this study are as stated below
(1) On Incremental Earth Pressure Distribution
When surface load is imposed on improved soil (a = 0cm, 10cm), the earth pressure has an incremental distribution where the earth pressure is higher at and around the central part and decreases in the directions of the earth’s surface and the batholith, respectively. In the case of the test object [θ= 15°], too, the value for the earth pressure reaches a maximum level at a point approximately 2H/3 away from the earth's surface and then decreases in the directions of the earth's surface and the batholith, respectively. In the case of the test object [θ= 30°], on the other hand, the value for the earth pressure reaches a maximum level at points above the central part and decreases in the directions of the earth's surface and the batholith, respectively.
When there is no surface load imposed on the improved soil, the values for the incremental earth pressure ([θ= 0°; a = 20 cm], [θ=15°; a = 30 cm], [θ= 30°; a = 40 cm]) have distributions similar to each other, increasing in the direction of depth. The value at each point is far smaller than when a = 0 and a = 10 cm.
(2) On Ground Contact Pressure Distribution
Due to the relationship between the surface load (q = 10kN/m2) and the ground contact pressure, the test object [θ= 15°] has a relatively uniform ground contact pressure distribution for every loading position. It has also been shown that the test object [θ= 30°] has the most unbalanced ground contact pressure distribution.
(3) On the Relationship between Overburden Loading and Displacement
The displacement that results from overburden loading for the test object [θ= 30°] is the smallest, it becoming larger for the test object [θ=15°] and for the test object [θ=0°], in that order.
