چكيده به لاتين
Improving soil quality and strength has long been a critical focus. Granular and loose soils pose significant challenges in executive operations due to their poor compaction properties, low bearing capacity, high permeability, and other limitations. Salt-sand sediments, which are widely distributed across various regions worldwide, cover approximately 15% of Iran's surface area and constitute one of the most important sediments in desert environments.
With the rapid expansion of urbanization and civil construction projects, engineers are compelled to construct in areas with inherently low load-bearing capacity, which can lead to substantial financial losses and safety hazards.
The first and most readily available additive for enhancing strength properties of soil is cement. However, its production and application pose significant environmental concerns. Today, numerous alternative additives are used worldwide, among which biopolymers have gained increasing attention. Biopolymers not only improve soil properties but are also environmentally friendly and eliminate the ecological drawbacks associated with cement.
In the present study, the biopolymer under investigation is called casein, which is a natural protein derived from milk. The present study is an attempt to evaluate the strength parameters of granular soils modified with casein in order to compare and analyze the performance of casein in problematic and collapsible soils across the country, ultimately exploring its potential as an alternative to cohesive construction materials such as cement in future applications.
To evaluate the soil strength parameters, a series of laboratory tests including direct shear tests, California Bearing Ratio (CBR) tests, wet and dry durability tests, and rain splash tests were selected. These tests are conducted on granular sandy soil 161 from Firouzkouh, modified with sodium chloride (NaCl) with different concentrations (2.5%, 5%, 10%, and 15%).
In the direct shear test, the objective is to determine the strength parameters (cohesion and the internal friction angle) of modified soil and generating key plots, including Shear stress versus vertical stress at peak strength, Shear stress versus shear displacement and Vertical displacement versus shear displacement.
In the CBR test, the objective is to determine the shear strength of the soil under a specified moisture content and weight. The CBR value is defined as the ratio of the applied load required to penetrate a standard plunger into the soil sample to the corresponding standard load required for the same penetration in a reference material. Additionally, wet and dry durability tests are conducted to obtain a useful dataset on the strength characteristics of the modified soil. Finally, the rain splash test is performed to examine the surface stabilization efficiency of the casein treated soil against untreated samples.
The experimental results generally indicate that casein enhances soil durability. The results also show that this additive can not only improve bearing capacity of soil but can serve as an effective technique for stabilizing desert sands.
