Abstract
The present paper aims to improve shear strength parameters: cohesion (c), and angle of internal friction (∅) for sandy soil treated by additives before and after soaking. The samples of sandy soil were obtained from Karbala city and then classified as poorly graded sand (SP) with relative density Dr (30%) according to the system of (USCS). The experiment has three stages. In the first stage ,the soil was treated with three different percentages of cement (3 ,5 and 7%) of dry weight for the soil with three different percentages of water content (2, 4 and 8%) in each above percentage of cement, while the second stage includes (2%) of lime from soil weight mixed with each different percentage of cement . In the third stage, (50%) of polymer of cement weight was mixed with each different percentage of cement. An analysis of behavior sandy soils treated by additives was carried out with the Direct Shear Tests. All the samples were cured (3) days before and after soaking. The results of the experiment showed that increase in shear strength parameters of sandy soil; especially the angle of internal friction with the rate value (16.6 %) of cement only, (21.88 %) of cement with lime , (20.3%) of cement with the polymer before soaked condition. After soaking condition, it was increased with the rate value (14.3%) with cement only, (23.57%) of cement with lime, and (15.38%) of cement with the polymer as compared with soil in the natural state.
Highlights
Ground improvement is a process that aims to enhance the engineering properties of the soils and generate an improved constriction material by increasing soil strength, durability, stiffness, and decreasing permeability and compressibility of sandy soils
The results of effect (W:C) with soil treated by cement on the shear strength parameter explained that the angle of internal friction increased when soil was treated by cement with 4% (W:C) of the rate value between (10-16.6%); the optimum moisture content (OMC) is 4%
The comparison between shear strength treated by cement only and shear strength parameters treated by mixture cement with lime before soaking can be summarized as follows: 1. Shear strength of soil treated by mixing cement with lime was increased more than the soil treated by cement only
Summary
Ground improvement is a process that aims to enhance the engineering properties of the soils and generate an improved constriction material by increasing soil strength, durability, stiffness, and decreasing permeability and compressibility of sandy soils. Many researchers relatively have studied the effect of the stabilization agent on shear strength parameters Mitchell [1] showed that stabilization agents increase the effect of cohesion. Other researchers such as Lo, SR, and S PR Wardani [2] found out that the soil treated by cement presented a significant increase in both internal friction angle and cohesion. Ziaie-Moayed et al [6] conducted research to improve the saline soils before and after soaking by using cement and polymer on shear strength and they concluded ;(1) the strength of soil specimens are increased by adding cement and resin epoxy and (2) saline materials have an effect on the strength of the soil specimens; in addition, the shear strength of the soil decreased after soaking
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