Applied Mechanics and Materials Vols. 170-173

Abstract: The site is located at mileage 50K +650, Tai-174 Road near the mountain slopes. The vertical range is about 150m and the area is 30000 m2. The present study adopted the finite element method program "the PLAXIS 8.2” to analysis. The contents include: (1) To analysis the slope stability on condition that to increase groundwater level is the antecedent of building a function which is the least squares difference between changing slope value and calculated value. Then this study explored the effect of the soil parameter values in different soil layer, parameter sensitivity, to the objective function. Simultaneously, this study sought the optimal parameters of the finite element model in this site in order to be the post-conditions analysis; (2) In order to prove the correctness, this study analyses and compared the data from sliding surface and tilt tube.

Abstract: Inclined angles of piles and applied loadings have serious effect on the pile’s bearing capacity and settlement. In order to reveal this effect, this paper uses the nonlinear finite element software Adina 8.2 and analyzes the settlement characteristics and the influence factors on the settlement of inclined pile subjected to inclined loadings. From the analysis, it can be seen that: at given pile-soil physical properties, the settlement of inclined angle of the pile is smaller than that of the pile installed vertically subjected to vertical loadings; it is not good for larger inclined angle of inclined pile when the pile subjected to inclined loadings and the pile top settlement is always smallest when the inclined angle of the loadings agrees with that of the pile; The location of the horizontal stress balance point is related to the factors, such as loading value, pile inclined angle, et al., when subjected to vertical loadings. The conclusions obtained can have some reference value for the design and construction of inclined pile that subjected to inclined loadings.

Abstract: The change of Shanghai soft soil’s density with drainage time during foundation pit dewatering was investigated, through taking samples in each soil layer to be laboratory tested after the groundwater level of observation hole in project site had been lowered below the position soil sampled for at least 5 days. Experimental results show that groundwater included in drainage zone couldn’t be discharged immediately with the drop of groundwater table, which may be named as “lag draining” phenomenon; soil’s water-holding density can also be deduced from soil saturated density and specific field except directly measured from laboratory test. The effect of engineering pumping will reduce the discrete of soil density distribution; a centralized distribution of soil density emerges after dewatering.

Abstract: This paper studies the bearing capacity parameters of a single pile of hammering sunk shaft rammer pile with engineering practice, proposes three parameters: the shape factor of expanded head α, correction factor of pile tip resistance β and the uplift height h, modifies the calculation formulae of bearing capacity of a single pile and expanded head based on these parameters, and validates the application of these parameters with engineering practice..

Abstract: Choosing an accurate soil model is the key point in calculating the foundation settlement. The commonly used models in engineering practices are the Winkler’s model, elastic half space model and finite compressible layer model. Among these models, the finite compressible layer model is widely used in the designing of raft foundation. As the finite compressible layer model can not reflect the nature of the in situ soil and the nonlinear settlement, in this paper we try to modify the elastic modulus E by the secant modulus in order to improve the soil model of finite compressible layer.

Abstract: The floor heave is one of soft rock roadway distortion. Based on soft rock supporting theory and engineering practice, the program bolt-mesh-anchors and floor corner, bolts coupling support to control floor heave of the soft rock roadway is proposed. Numerical simulation results show that bolt-anchors can mobilize the strength of the deep adjacent rock, at the same time, and properly arranged floor corner bolts with high bending rigidity can cut the slip-line field and achieve the goal of controlling floor heave effectively.

Abstract: At present, foundation bearing capacity used in the practical engineering design is often based on controlling strength, if such it may produce some problems, even accidents. In this article, using Midas-GTS and FLAC3D software to analyse a simplified example of a problematic engineering, we obtain the result that under the conditions of enough strength; the whole structure generates a lot of uneven settlement. On this basis, it explains that the lack of bearing capacity of foundation ideology. And we proposed explicitly foundation bearing capacity should include deformation, in hopes that the influence on the later engineering.

Abstract: the stress wave speed is the necessary condition to make sure pile length and pile defects position in low strain integrity testing of foundation pile with the stress wave echo method. Quantifying the stress wave speed is very difficult, because it is affected by multi- factors. This has been choke point developing test technology of foundation pile. In the paper, some factors influencing the stress wave speed were analyzed according to stress wave theory and experiment results, the quantity relations of the stress wave speed in pile and time and concrete age were made sure. lastly, five brief methods to quantifying the stress wave speed in pile were presented to control pile quality for test engineers according engineering practice.

Abstract: In order to analyze the microscopic shear mechanics behavior of sands, a numerical simulation is carried out in sand direct shear test with commercial DEM software PFC2D. By compiling FISH function, PFC2D is able to visualize principal stresses and their inclination inside the sample. In the simulation, particle rotation gradient and particle displacement vector are observed to analyze the microscopic formation mechanism of shear band. The strain and deformation is concentrated in a band whose thickness is about 10 times of average particle diameter and the band is close to the shear plane. The porosity ratio in shear band is higher than other parts of the sample with shear process.

Abstract: The stability and deformation characteristics of the pile foundation in the Karst region of the super big railway bridge Chaogou under different loading levels are analyzed using the FDM-software, FLAC^3D. In the analyses the socketed depth of piles, the properties of soil and rock mass, the scale, space position and filling situation of the Karst caves and the features of the contact interfaces between piles and soil and rock mass were taken into account. The research results show that the original design of the pile foundation is safe and the safety coefficient is greater than 2. The bond strength of the contact surface between pile and soil and rock is a controlling factor for the stability of pile foundation. Therefore, injection after construction is suggested to be used when needed, in order to increase the bond strength of the contact surface. The research leads to a conclusion that the mechanisms and the characteristics of the rock socketed piles can be more clearly interpreted in numerical analyses by referring the principle of the interaction between piles and rock, pile foundation and Karst, resistance of both pile ends and sides.