مقاله انگلیسی رایگان در مورد مدل سازی تنش در مقابل رفتار نشست فونداسیون سطحی – الزویر ۲۰۱۸

The bearing capacity of saturated soils can be estimated by extending either the effective stress approach (ESA; Terzaghi, 1943) or the total stress approach (TSA; Skempton, 1948). Criterion for determining appropriate approach between the ESA and the TSA are based on the soil type and drainage condition of pore-water during the loading stages. Shallow spread footings are commonly used as foundations of light structures. In many cases (especially in arid and semi-arid regions), the water table is relatively deep, and the pressure bulb typically lies within the vadose zone where soils are in unsaturated condition with negative pore-water pressure. Soil desaturation associated with lowering the natural ground water level or water evaporation from the soil surface results in an increase in the bearing capacity compared to the saturated soil condition. Various research related to the bearing capacity of unsaturated soils suggest that this increase can be attributed to the influence of soil suction (Broms, 1964; Steensen-Bach et al., 1987; Fredlund and Rahardjo, 1993; Oloo et al., 1997; Costa et al., 2003; Rojas et al., 2007; Balzano et al., 2012). Nevertheless, there are still uncertainties as to which approach (i.e. ESA or TSA) is more appropriate in the reliable estimation of the bearing capacity of unsaturated soils. Vanapalli and Mohamed (2007) and Schanz et al. (2011) showed that the bearing capacity of unsaturated sandy soils can be reliably estimated extending the ESA taking account of the influence of matric suction. Oh and Vanapalli (2013a) conducted model footing tests in unsaturated glacial till (i.e. Indian Head till) and concluded that the TSA based on the unconfined compressive strength of unsaturated soils can provide a more reasonable bearing capacity of unsaturated cohesive soils. These research studies related to the bearing capacity of unsaturated cohesionless and cohesive soils indicate that the bearing capacity of unsaturated soils should be estimated considering the type of soil and the drainage conditions of pore-water and poreair. The ESA and the TSA for unsaturated soils are designated as the modified effective stress approach (MESA) and the modified total stress approach (MTSA), respectively. In-situ plate load test (PLT) is one of the most reliable testing techniques for estimating the bearing capacity of shallow foundations. In-situ PLTs are typically carried out on soils that are in a state of unsaturated condition; hence, there are uncertainties in analyzing the in-situ PLT results in terms of scale effect and matric suction distribution profile with respect to depth (Oh and Vanapalli, 2013b). For this reason, numerical analysis is commonly used as an alternative to the in-situ PLTs to estimate the bearing capacity of unsaturated soils.