Advanced Materials Research Vols. 594-597

Abstract: Well pumping leads to both horizontal and vertical displacement, and fluctuation of groundwater level can cause serious damage to structures in a lagre affected area. Ground behaviors due to seepage force in traditional methods were rarely considered. This paper presents a numerical solution of ground displacement behaviors due to unsteady groundwater flow in unconfined aquifer by considering the effect of capillary zone based on the saturated-unsaturated seepage theory, and the numerical simulation code implemented by FORTRAN is applied to predict the flow velocity distribution and the results of ground displacement. The model uses the finite element method and finite difference method to study the problem. The analysis shows that the seepage force and the effect of capillary zone play a very important role in both seepage flow and displacement field.

Abstract: Microstructure is a important index of soil physical, mechanical and engineering properties, SEM images and computer image processing technology make the soil microstructure research developing rapidly in recent years, but the researches on the influence factors and important degree are rare. Process the images form scanning electron microscopy test with the image processing toolbox of MATLAB. Fractal dimensions, porosities and pore size distributions are calculated in different analyzing windows, thresholds and magnifications. The results show that:1) As the results of the experiment influenced greatly by the smaller analyzing windows, in order to get the real calculation value, the medium section was processed; 2) Fractal dimension values are less influenced than porosities and pore size distributions by different thresholds; 3) Too big magnification can cause inaccurate fractal dimensions. Porosities and pore size distributions are inverse growing with increasing of magnification.

Abstract: Based on the experimental study of rotary filling piles with large diameter subjected to axial load in deep soft soil, the bearing capacity behavior and load transfer mechanism were discussed. Results show that in deep soft soil foundation, the super–long piles behave as end-bearing frictional piles. The exertion of the shaft resistance is not synchronized. The upper layer of soil is exerted prior to the lower part of soil. Meanwhile, the exertion of shaft resistance is prior to the tip resistance. For the different soil and the different depth of the same layer of soil, shaft resistance is different.

Abstract: This paper summarizes the importance of strain monitoring, points the characteristics and the main difficulty in strain monitoring of geotechnical. From the current situation in Strain monitoring of geotechnical engineering, it analyzes and summarizes the principle and the practical application of the advantages and disadvantages of strain gauges, fiber Bragg grating and distributed optical fiber. Finally, it designs an overview of geotechnical engineering strain monitoring system, nine principles of strain monitoring system to be put forward, and the direction of geotechnical engineering is the development of strain monitoring system and application.

Abstract: By establishing numerical simulation model of SPBH and comparing dynamic response of four kinds of coal-rock combination media subjected to three different stress waves, changes law of the reflected wave, incident wave, strain and strain rate were obtained. The results show that rock-rock combination has almost the same rules of reflected waves as rock-coal combination, coal-coal combination and coal-rock combination, while the coal-coal combination has the largest peak of reflected wave, followed by the coal-rock combination and the rock-coal combination, and the rock-rock combination ranks last. With increasing incident wave peak, the coal-rock combination weakens the peak more apparently. Strain softening occurs in coal samples under stress wave of peak value with the law that strain rate firstly increases, and then maintains a constant value, continues to increase and then decreases, increases reversely and then decreases. Constant strain rate of the phenomenon over time occurs. The results provide guidelines for both the study on propagation mode of stress wave in coal and rock combination media and the prevention of mining-induced dynamic disasters.

Abstract: In accordance with settlement observation data of weak interlayer foundation in The North China Plain, finite element model was made to analyze vertical settlement and horizontal deformation by MIDAS/GTS software. Then, Influence factors of subgrade settlement were studied through changing the fill height, crust layer thickness and compression modulus. The results show that crust layer has the board supporting and closing the substratum functions during the period of loading and a relatively short period after loading. The maximum horizontal deformation occurs in weak interlayer rather than the ground surface. The horizontal deformation increases generally with the increase of the fill height. When the crust layer thickness increase, its settlement grows larger and the settlement of soft soil layer has the decrease trend. The settlement of crust layer and weak layer is decreased with the compression modulus increase of crust layer. It explains that the shell effects of crust layer increase with the compression modulus increase of crust layer.

Abstract: The shear stress of prestressed anchor cable is unevenly distributed along anchoring length.Based on the load transfer behaviors of bolt,the solutions for distribution of the shear stress in pre-stressed cables are derived.And the mechanical characteristics are discussed for the influences on the shear stress distribution.The calculated values are compared with the results of the filed tests,and good agreements are obtained.

Abstract: According to the similarity theory, this paper established a geometric similarity 1:10 and 3 × 3 rigid pile composite foundation pile group model. Pile strain , cushion deformation and flask displacement were obtained through pasting resistance strain gauges in pile, embedding strain gauge in cushion, connecting to displacement sensor at out of flask, etc., basing on pseudo-dynamic test method. These date were analyzed and studied, and then can conclude the response pattern under earthquake action on rigid pile composite foundation, which provide a basis for application of rigid pile composite foundation in practical engineering.

Abstract: The static load test of composite foundation was simulated by using the nonlinear finite element programs, and the changes of the pile-soil stress ratio and the pile and soil settlements as well as the plastic deformation of composite foundation were analyzed. The simulation results show that: the cushion of flexible pile composite foundation can effectively regulate the pile-soil stress ratio and make the bearing capacity of the lime soil pile and the soil between piles give full play at the same time. The cushion has a distinct role in reducing the pile settlements, however, has little effect in reducing the soil settlements. The reasonable cushion thickness is about 300mm. The composite foundation will emerge local shear failure when it reaches the ultimate bearing capacity. Reducing the pile spacing can increase the ultimate bearing capacity, and the rate of increase shows a gradually increasing trend.

Abstract: Subgrade settlement is a complex systematic process. Frequently used single point forecasting models can’t consider the correlation of settlement between the discrete monitoring points, so that it can’t represent the integrated deformation regularity of subgrade. For resolving this problem, this paper extends the single point GM(1,1) model into a multivariable grey model (MGM(1,n)), and completes the programming with MATLAB. Finally, A MGM(1,3) model is established to predict the subgrade settlement, and the result of the model is more precise and effective than the single point GM(1,1) model through a practical application.