نوع مقاله : پژوهشی
نویسندگان
دانشکدهی مهندسی عمران و محیط زیست، دانشگاه صنعتی امیرکبیر
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
The Coefficient of Subgrade Reaction was introduced in the form of a Set of Springs model by Winkler during the 19th century. In this model, the subgrade is modeled as a set of springs with a stiffness of $k_{s}$ per unit area of the foundation carrying the structural load. In other words, the Contact Pressure to Settlement ratio for every point located in the contact zone of soil and foundation is called the Coefficient of Subgrade Reaction, or $k_{s}$. This ratio explains the interaction of soil and foundation, and it can be used for
calculation of shear and moment distributions in the foundation.
The model has been used by structural designers for decades, who have improved it to calculate stresses under flexible foundations, like continuous footings or raft foundations, as well as concrete pavements subjected to wheel loads. Therefore, proper estimation of $k_{s}$ for raft foundations is essential for structural engineers. A commonly used method for in situ direct measurement of $k_{s}$ is the Plate Load Test (PLT). As the PLT is carried out on a small scale, the influence zone is small. The results cannot then be used directly for large
scale calculations. Among the commonly used equations for correlating the PLT results to $k_{s}$
for large raft foundations are those proposed by Terzaghi (1955).
The main objective of this paper is investigating $k_{s}$ for cemented granular materials using a numerical model. The results of three plate load tests are used for verification purposes, and calibrating the FEM numerical model used for predictions. The effects of the change of foundation size and thickness on the value of $k_{s}$ are briefly discussed.
The results indicate that the Terzaghi (1955) equation for Clay estimates an acceptable value for $k_{s}$
in cemented granular soils similar to Tehran alluvium.
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