Entity

Time filter

Source Type


Wang H.-X.,Shanghai Urban Construction Municipal Engineering Group Co.
Yantu Lixue/Rock and Soil Mechanics | Year: 2016

In dealing with geotechnical engineering problems with the traditional soil mechanics, the elastic mechanics approach is often used to calculate the stress distribution in soil. The calculation of the stresses in soil is usually based on simple Boussinesq's solutions which are derived on the assumption that the loading acts on the ground surface. However, building foundations are generally buried in a certain depth beneath ground surface. In this case, the Mindlin solution is more suitable to calculate the stress distribution. The equations for calculating stresses in a semi-infinite elastic solid subjecting to a vertical rectangular and strip uniform load are significant for many geotechnical problems, such as the calculation of foundation settlement and the analysis of the influence of excavation size on its stability and deformation. Although all the equations have been presented in Reference [1-2] by Yuan Ju-yun, several errors are found in these equations. Based on the Mindlin's formulas, the calculation equations for calculating stress in the soil subjecting to a vertical rectangular uniform load beneath the surface are derived by the integral method again. Furthermore, the equations for strip load in similar case are deduced, both of which are different from those given in Reference [1-2]. Eventually, the correctness of two groups of formulations is verified by the numerical integration. © 2016, Academia Sinica. All right reserved. Source


Wang H.,Shanghai Urban Construction Municipal Engineering Group Co.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2015

Common shapes of excavations include strip, rectangle, circle and pistol. When other conditions are the same, excavations with different shapes have different safety coefficients of heave-resistant stability. However, all recommended methods from existing guidelines for heave-resistant stability analysis ignore the influence of excavation shape on the safety coefficient. In this paper, based on an unloading model of excavation, a new safety coefficient has been defined which takes into account the plane shape, dimensions and embedment ratio. The safety coefficients for various excavation shapes, such as strip, rectangular and pistol, can be calculated analytically based on the definition. For circular excavations, the coefficient can be calculated by numerical integration, so the challenging problem of analyzing the stability of circular excavations is solved. When the diameter of circular excavations is large enough, the safety coefficient will be identical to that of extra wide strip excavations, indicating the wide applicability of the proposed safety coefficient. For excavations with a small embedment ratio of retaining wall in clay stratum, the proposed safety coefficient converges to the result from the Terzaghi method. The variation of the bearing capacity coefficient of foundation soil calculated using the proposed method is consistent with that of recommended values, and its rationality can be validated by field data and results from the strength reduction method. Field statistics indicate that there is a definite relationship between the safety coefficient and the deformation of circular excavations and the relationship can be used to determine the acceptable safety coefficient of excavations. © 2015, Science Press. All right reserved. Source


Wang H.-X.,Shanghai Urban Construction Municipal Engineering Group Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

There is a large error in calculating foundation settlement of small size by using the layerwise summation method based on consolidation tests, while the calculation of foundation settlement based on the plate load tests can not reflect the deformation characteristics of the foundations of large size. Considering the theoretical and experimental basis in calculating the foundations settlement under large-area loads by means of the layerwise summation method based on the e-p compression curve, which can be deemed as the upper limit of the practical foundation settlement with the same base pressure, while p-s settlement curve can reflect the deformation characteristics of the foundations of small size, which can be deemed as the lower limit of the practical foundation settlement with the same base pressure. Based on the above theory, an interpolation algorithm for the foundation settlement is proposed, and the issues of determining the modulus of compressibility are transformed into those of finding the interpolation functions. This algorithm can reduce the absolute error produced by the traditional algorithm to the relative error within a certain range so as to improve the calculation accuracy of foundation settlement. Furthermore, a method to predict the foundation settlement is suggested by adopting two load test results under different load plate sizes, whose rationality is verified through four-group plate load tests on the same foundation. And the interpolation function of a circle foundation is derived and analyzed to show the process of foundation settlement calculation through the interpolation method. The analysis results show that the foundation settlement curves gradually change from concave to convex when increasing the size of foundations. The proposed method combines the results of the consolidation tests and plate load tests, which can reflect the settlement characteristics of the foundations of different sizes. It is suitable for promotion in engineering practices with its clear theoretical and experimental basis and simple and convenient calculation process. Source


Wang H.-X.,Shanghai Urban Construction Municipal Engineering Group Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2016

In order to consider the effect of shape and depth of foundations in estimation of bearing capacity of foundation soils and stability analysis of excavations, an approximate analytical method to calculate the bearing capacity factor Nc is proposed. According to this method, the estimation of bearing capacity of foundations with different shapes and depths can be unified into the same equation. If the depth of the plastic zone is properly modified, the calculated results will be very close to those from the laboratory test data and the field investigations. It was proven by this method that the value of Nc in the calculation of bearing capacity is identical to that in the analysis of excavation stability. On the basis of the method, the influence of embedment depth of the enclosure structure can be taken into account in the Terzaghi's method for analysis of the stability against heave of excavations. Moreover, an approximate approach to estimate the bearing capacity factors of shallow foundations is also put forward. © 2016, Chinese Society of Civil Engineering. All right reserved. Source


Wang H.,Shanghai Urban Construction Municipal Engineering Group Co.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2013

Engineering practices and model test results all indicate that overburden soil stratum is often able to withstand greater head pressure than the pressure of its own weight. Currently, no relevant theory can explain this phenomenon. The concepts such as generalized buoyancy, generalized buoyant unit weight and generalized hydraulic gradient are proposed by considering adsorptivity of soil particles to pore water as well as considering connectivity of bound water; and then specific calculation method is given, explaining the physical meaning of the parameters such as ξs, ξv and ξ used in the calculation and recommending the estimating method of ξv. The tests envisaged on measuring ξs and ξv are also given, then the relationship between ξs and initial hydraulic gradient ib is established. Aforesaid calculation method takes the different natures of soil into account. For sand and loose soil, generalized buoyancy, generalized buoyant unit weight and generalized hydraulic gradient are changed into Archimedes buoyancy, traditional buoyant unit weight and hydraulic gradient. Further, calculation method of seepage force in different soils has been given. In the end, the unified expression of failure conditions of soil under the action of groundwater is got, which can interpret several different failure modes of soil under the action of groundwater. According to this theory, the calculating method of anti-seepage stability and the stability of resistance to the confined water of foundation pits should be amended and the current calculation method can only be applied to sand and loose soil. Some conclusions derived by using this calculation method to analyze the stability of soil in groundwater under different strata combinations are different from traditional arguments. For example, when analyzing the embedment depth of enclosure structures, if there is no impact of confined water, the seepage failure of the foundation pit is difficult to occur in the clay stratum and the ability of foundation pits to resist seepage failure in the silt stratum is better than that in sand layer. When analyzing the anti-upbursting of confined water in foundation pit, the traditional ballast-balance calculation is unsafe to the overburden soil stratum with permeability, while for the overburden soil stratum of confined water stratum containing a certain amount of silt, its ability to resist the confined water pressure is relatively increased. Finally, based on the result of the paper, the unified calculation theory on soil-water pressure is amended. Source

Discover hidden collaborations