Advanced Materials Research Vols. 243-249

Abstract: Prediction on red clay foundation settlement was put forward, using hyperbola method, exponential curve method and Hushino method, based on field data. Furthermore, Verhulst model, Gompertz model, Logistic model and Weibull curve were adopted in foundation settlement prediction. Subsequently, variable weight combination method and optimized combination model was studied to get more accurate prediction results. Finally, red clay foundation prediction of high speed railway was proposed.

Abstract: Static load tests were carried out with Osterberg method on 3 bored piles formed in Liao River Bridge. Bearing capacity, base resistance and frictional resistance were obtained before and after base grouting. Based on the test results, the ultimate bearing capacities of piles were increased for 14.74%~43.87%, that of pile bases were increased for 89.57% ~ 163.49% and the frictional resistances were most increased for 31.20%. The pile bearing behavior was improved. Not only base resistances were improved after grouting, but also frictional resistances were improved by bettering the characteristics of soils and interfaces between piles and soils. After grouting, pile base resistance ratio of pile bearing capacity increased, and some frictional piles changed into end-bearing frictional piles. The frictional resistance of lower pile increased more than that of upper pile after grouting. The slurry penetration height of base grouting had a certain range, which was affected by quantity of mortar intrusion, grouting technology, grouting pressure and geological structure.

Abstract: This paper introduced the application of Self-balanced Test Method for Bearing Capacity of Foundation Piles on a construction project of Gui Zhou province, while sorting out and analyzing the test data, the application results indicates that the method of the static load test is an effective and convenient method of testing technique. it can popularize the use in the similar projects.

Abstract: Wind erosion mechanism is studied through interior wind erosion wind tunnel experiment for desert highway. The anti-wind erosion ability of Aeolian soil subgrade slope is equivalent to the variation of microstructure characteristics and shearing strength of Aeolian soil. Microstructure characteristics will be quantified analysis through scanning electron microscope and image analysis software for subgrade slope, and microstructure parameters are picked-up for wind erosion fore-and-aft. Aeolian soil’s Shearing strength and wind erosion depth are investigated at different position of windward slope during a long-time wind-blown. Then, wind erosion mechanism of Aeolian soils subgrade slope is clarified from two aspects of micro and macro, wind erosion influence depth is determined for certain environmental condition. Taking desert highway subgrade as an example, the results indicate that: the disturbance to the flow field enhances with the increase of slope ratio and subgrade height, wind erosion of the windward slope is severe. The anti-wind erosion ability on windward slope is weak obvious with the decreasing of soil’s water containing, the increasing of wind velocity and the blow time prolong. Shearing strength of Aeorian soil is gradually decreased from slope surface to its interior, from bottom to top of windward slope. According to environmental condition local, when average wind velocity is 11m/s and natural water containing is 2%, wind erosion depth is about 15mm on the top of slope which is 1/11 of subgrade height, relative to 10mm on the mid of slope. The conclusions drawn from micro and macro are proved the wind erosion mechanism of Aeolian soils subgrade slope perfectly.

Abstract: In this paper, in order to analyze the capability of squeezed branch pile under different work condition and the cooperation mechanism between the pile and soil, non-liner numerical simulation was carried out using ANSYS. In the finite element model, the elastic-perfectly plastic Drucker-Prager material was assumed for soil. Contact interface elements were placed between the pile and soil. It showed that the squeezed branches took lots of the load, and the ratio it took was related to the load and the elastic modulus of soil; the plastic section of the soil was run-through from bottom to the top; the horizontal displacement of the top soil was moved to the pile, but the horizontal displacement of the soil of the bottom was moved away from the pile; the squeezed branch will break away from the soil above the squeezed branch when the load was at a certain value.

Abstract: The new CFG pile-board structure composite foundation is a ground treatment technique based on CFG pile foundation and pile-board structure composite foundation. It can make full use of the load distributing function of board, the bearing capacity and the deformation compatibility of soil between piles, by taking advantage of the pile-platform-soil interaction. A part of soft ground in a high-speed railway was taken as the engineering background and study object. The settlement controlling effect of common CFG pile ground and new CFG pile-board structure composite foundation were analyzed by finite element numerical method, and various factors to the effect on settlement-controlling were discussed. Pile-soil stress ratio of CFG pile and reinforced concrete pile were studied. Some useful conclusions of the numerical simulation of the new CFG pile-board structure composite foundation were obtained.

Abstract: For rock-like materials, large diameter SHPB (Split Hopkinson Pressure Bar,SHPB) is necessary and essential in dynamic test. Based on the finite element software ANSYS/LS- DYNA, the transmission of different stress pulse waveform in large diameter bar was simulated and the loading waveform dispersion effect was investigated in this paper. Three typical stress pulses (rectangular waveform, triangular waveform and half-sine waveform) with the same duration time and maximum stress amplitude value were loaded on input bar of SHPB. The time-stress curves of different transmission distance on input bar were traced and recorded and four specific aspects were discussed respectively. Compared with rectangular waveform and triangular waveform, the results of numerical analysis indicated that there isn’t pulse waveform dispersion for half-sine waveform to transmit in large diameter SHPB and there is enough increased time to satify stress equilibrium before rock-like materials failure. The half-sine stress wave is able to meet the one-dimensional assumptions in the propagation process and can be used in large diameter SHPB test.

Abstract: To investigate the rainfall-induce the seepage field of a high slope and effect factors, the theory of saturated-unsaturated infiltration was employed, and the numerical model of slope infiltration subjected to the rainfall are developed and programmed. The numerical results shown that, (1) With the increasing of the rainfall duration, rainfall water infiltration formed a transient saturated zone at slope surface, when the moist frontal surface reached to the groundwater level, the rainfall water would supply the groundwater. (2) Each effect factors on the seepage field play a strongest roles on the slope toe, weaker role on the middle part slope and weakest role on the top slope. (3) The longer rainfall duration, the deeper of infiltration depth. It also be deeper with the larger rainfall intensity, coefficient of permeability, the initial moisture content of the surface and the surface waterlogging depth. (4) The effect on seepage field would be faintly and could be ignored when the rainfall intensity was greater than 65.9mm/h and the surface waterlogging depth is greater than 0.3m. All above could provide technical ideas for analyzing slope seepage field under rainfall and accumulate fundamental data for early warning and preventing mud-rock flow and landslide.

Abstract: By using finite difference software FLAC3D, the displacement field and stress field of the long-short-pile composite foundation were studied, as well as the distribution of axial force, neutral position and penetration amount. The effects of the main parameters of long-short-pile composite foundation on its working properties, such as the modulus and thickness of the cushion, the length and quantity of the long pile, are investigated in detail. The results show that the modulus and thickness of cushion have less effect on the foundation settlement, while they can affect the pile-soil stress ratio significantly. Moreover, increasing the number of piles can control the foundation settlement effectively. The stresses in upper soil layer can be transferred to lower soil layer effectively, with the increasing of the number of long piles. Then the foundation settlement can be reduced correspondingly. While the variation of the number of piles has less effect on the stress field when the number of piles reaches a certain extend, and the reduction of the foundation settlement tends to slow down. Further, the foundation settlement decreases with the increasing of long-pile length. Finally, based on the foundation settlement control, the recommended values of parameters are given.

Abstract: Based on the end bearing capacity and friction capacity obtained from high strain dynamic test, an adjusted equation was provided to calculate the pile load capacity. The equation was corrected again by pile load test results. Therefore, a suggested equation was finally established. Practical experience showed that, the corrected equation of cone penetration test method to estimate the load capacity of single pile performed better than that in the national code.