Methods for Estimating the Ultimate Bearing Capacity of Layered Foundations

The Meyerhof and Hanna′s(M-H) method to estimate the ultimate bearing capacity of layered foundations was improved. The experimental results of the load tests in Tianjin New Harbor were compared with predictions with the method recommended by the code for the foundations of harbor engineering, i.e. Hansen′s method and the improved M-H method. The results of the comparisons implied that the code and the improved M-H method could give a better prediction.

Elastoplastic numerical analysis of layered soil foundation under the rectangular shallow footing subjected to vertical load

Finite and infinite coupled element method was used to analyze the strength and deformation in layered soil foundation which was under the rectangular shallow footing subjected to vertical loads. In the numerical analysis, the footing was assumed to be elastic; the soil was assumed to be elastoplastic and the Drucker-Prager constitutive model was applied to describe its mechanic behavior. Corresponding program was employed to compute six kinds of layered soil foundations constituted by different soil layers. The conclusions which are useful in the theory and practice were made according to the analysis of the computation results.

Numeric simulation analysis of load-settlement relation of pile in layer foundation

Considering the level distribution of soil layers, the soils surrounding pile are simulated with level finite layer elements. Supposing that the vertical deformation of the soil elements surrounding pile varies in the form of exponent function with radial distance, and considering the nonlinear constitutive relation of stress and strain, the stiffness matrix is established. The mechanics behavior of the pile—soil interface is simulated with a nonlinear interface element. This method can truly express the behavior of the pile-soil system. The load-settlement relation Q-S curves of two big diameter prototype piles on bearing test are analyzed, and satisfying results are obtained. This method is reasonable in theory and feasible in engineering.

Calculation and Analysis of Bearing Capacity of Double-Layer Foundation Based on Prandtl Assumption

Based on the basic concept of Plandell's assumption,the plasticity balance principle is applied to analyze the bearing capacity of the two-layer foundation,and the formula of bearing capacity of the two-layer foundation is obtained.The variation of bearing capacity of the foundation under different soil conditions is analyzed,and different calculation parameters are obtained.The effect on the ultimate bearing capacity of the two-layer foundation.The study found that:(1)For homogeneous soils,the formula obtained in this paper is the same as the Plandell formula;(2)the cohesive force of the soil,the soil bulk density above the foundation,and the aspect ratio have less influence on the bearing capacity of the foundation than the internal friction angle.Much;(3)The upper and lower layers of different strength ratios have different critical depths and increase with the increase of the relative strength of the upper layers.(4)This paper assumes that the foundation is completely smooth and ignores the influence of the bulk density of the foundation soil,which is not consistent with sand.

Dam foundation excavation techniques in China:A review

A protective layer(PL) is commonly reserved above foundation surface to protect the underlying rock mass during dam foundation excavation. In China, the PL of dam foundation is conventionally subdivided into two or three thin layers and excavated with the shallow-hole blasting method, even by pneumatic pick method in case of soft rock mass. The aforementioned layered excavation of the PL delays the construction of the whole project. After nearly 30-year practices, several safe and effcient methods for the PL excavation of dam foundation are gradually developed. They include shallow-hole bench blasting with cushion material(SBC) at the bottom of the hole, and horizontal smooth blasting(HSB). The PL is even cancelled on the condition that horizontal pre-split technique is employed during dam foundation excavation. This paper introduces the aforementioned two PL excavation methods(shallow-hole blasting and bench blasting) and horizontal pre-split technique of dam foundation without protective layer(HPP). The basic principles of blasting method, blasting geometry, charge structure, drill-and-blast parameters of typical projects are examined. Meanwhile, the merits and limitations of each method are compared. Engineering practices in China show that HSB is basically the optimal method for dam foundation PL excavation in terms of foundation damage control and rapid construction. Some new problems for dam foundation PL excavation arising, such as strong unloading and relaxation phenomenon that encountered in the gorge region of southwest China, are needed to be addressed; and the corresponding countermeasures are discussed as well.