New Method to Determine Critical Load and Plastic Zone for Strip Foundation   Shun-qun Li Department of Civil Engineering, Tianjin Institute of Urban Construction and Tianjin Key Laboratory of Soft Soil Characteristics and Engineering Environment, Tianjin, China e-mail: lishunqun@sina.com Shou-xi Chai Department of Civil Engineering, Tianjin Institute of Urban Construction and Tianjin Key Laboratory of Soft Soil Characteristics and Engineering Environment, Tianjin, China e-mail: chaishouxi@163.com Qing-xin Ren School of Civil Engineering, Shengyang Jianzhu University, Shenyang, China e-mail: renqingxin@sjzu.edu.cn Ying-hong Wang Department of Electronic & Information Engineering, Tianjin Institute of Urban Construction, Tianjin, China e-mail: wangyinghong66@sina.com
			ABSTRACT

In this paper, reasonable progresses are made from two aspects to determine critical load and plastic zone more precisely for strip foundations. First, a quadratic curve is established as Mohr’s envelope based on Coulomb’s strength theory and triaxial experiment results. Comparing with linear Mohr-Coulomb failure criterion, this one can reflect nonlinear increment of soil’s shear strength with normal stress increasing on failure plane. Then based on elastic theory, a formula is built, considering lateral force coefficient not equal to unit, to calculate proportional limit load, critical load and plastic zone. Together with geometric equation for boundary condition of plastic zone, solution can be obtained by digital approximation method. Comparing with the results from the traditional reference method, results of an example calculated by the proposed method have some difference. The reason for the reference method can not be used directly in practice is that proportional limit load and critical load from it are larger than the real one. The proposed method can be an ideal method to solve this issue soundly and perfectly.

Keywords: bearing power; proportional limit load; Mohr’s envelop; plastic zone; digital approximation method

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