Applied Mechanics and Materials Vols. 638-640

Abstract: The seepage is the main reason of many excavation accidents. Currently, most of the excavation designs ignore the seepage function or pay little attention on it. This paper focuses on the excavation’s stress and deformation influenced by the unsteady seepage, leading into the Van Genuchten seepage model and the Hardening-Soil constitutive model. And compare and analyze the different influences of flow field, stress field, displacement field and force caused by the steady and unsteady seepage

Abstract: The clay shear band analysis under plane strain condition were based on modified cam clay model in finite element software ABAQUS. Normally Consolidated Clay and lightly overconsolidated clay were analyzed in the article. Loading speed, size of soil specimen, different consolidation state (Normally Consolidated Clay and lightly overconsolidated clay) are considered. These factors have effect on the distribution of Pore water pressure, the effective stress path of nodes in shear band and out of shear band and the angle between the shear band and horizontal line. All the differentia and effects were used to analyze the production conditions and formation mechanism of shear band. The results show that size of clay specimen can influence the number of shear band. When the height-width ratio is large, the number of shear band will increase.

Abstract: This paper mainly introduced the grouting reinforced governance issues of old goaf of which exist building on the surface. Combined with the engineering example, the use of GTS software to identify mined areas and the the drilling histogram to establish three-dimensional geological model of gob region. Put forward to carry out positioning quantitative grouting technology on the goaf according to three-dimensional geological model, and strengthen the gob by using grouting method.

Abstract: Based on test method of numerical simulation, the bearing characteristics of large-diameter rock-socket pile with different super-thick pile caps have been analyzed, including the finite element model, Numeric Simulation of different heights of pile cap, Pile-soil load sharing, and stress flow analysis of thick pile caps. The results indicated that pile cap thickness has little influence on pile bearing capacity for the thick pile cap, when thickness of pile cap increases to a certain thickness, it would not affect the settlement characteristics under the pile caps. With the increase of the thickness of cap, the pile side friction load sharing value of pile side friction decreases, while the load sharing value of pile tip load increase, and soil force under the pile cap does not change with the different thickness of pile cap. However,it is advantageous to increase cap thickness to reduce tensile stress.

Abstract: Base on indoor model tests of three variable section pipe piles and two constant section pipe piles performed in foundation pit,the load transfer mechanism of two kinds of close-ended pipe piles are studied by comparing horizontal load-displacement curves, critical load and bending moment of piles. Results show that horizontal load-displacement curves change slowly and horizontal bearing capacity of valiable section pipe piles will be higher than constant section pipe piles with equal average diameters.Comparing with constant section pipe piles 1# and 2# with equal average diameters, unit volume horizontal critical bearing capacity of 3# and 4# are improved 8.7% and 34.2% respectively and which have different degrees of increse with improvement of valiable section ratio. Moreover,there are two maximum bending moment to valialble section pipe piles insteard of one to constant section pipe piles.To pipe piles 3#,4# and 5#, maximum bending moment ratio of big diameter pipe to small diameter pipe of valiable section pipe pile are 3.13、2.33 and 1.89 respectively. To pipe piles 3# and 4#, maximum bending moments of big diameter pipe are improved 26.8% and 28.4%.Howeverm,maximum bending moment of small diameter pipe are improved 54.1% and 111.8%.So,it is very clear that valiable section pipe pile is more reasonable than constant section pipe pile in bearing characteristics.

Abstract: Base on indoor model experiments of two constant section pipe piles and three variable section pipe piles performed in foundation pit,the load transfer mechanism of two kinds of close-ended pipe piles are studied by comparing load-settlement curves,shaft load distribution behaviors,skin resistance and resistance on pile end.Results show bearing capacity of variable section pipe piles is bigger than constant section pipe piles when settlements on pile top are equal.The bearing vertical capacity, unit volume bearing vertical capacity and availability of material of pipe pile will increase with improvement of average diameter and variable section ratio of variable section pipe piles.To variable section pipe pile, shaft load distribution suffered a sudden drop on position of variable section and shaft load distribution of small diameter pipe piles decrease quickly than constant section pipe piles.Resistance on pile end of variable section pipe piles are bigger than constant section pipe piles and resistance, ratio of resistance on pile end to bearing capacity of variable section pipe piles will increase with improvement of average diameter of variable section pipe pile. Action point of max skin resistance of variable section pipe piles are closer to pile top than constant section pipe piles .Max skin resistance will increase with decline with ratio of variable section pipe pile.If settlements on pile top are equal,force of skin resistance of variable section pipe piles are bigger than constant section pipe piles when the average diameters are same.

Abstract: According to the actual conditions of a high artificial backfill soil slope in a large thermal power plant’s in karst region with very developed caves in Guangxi Zhuang Autonomous Region, we carried out a number of slope monitoring works in order to timely and accurately getting of the stress and displacement distributions of slope retaining structure, to ensure safety of the thermal power plant, and to verify the safety and reliability of the slope design. Through a large number of monitoring data, obtained the development and change rules of the displacement, reinforcement stresses and anchors tension of the slope protection pile and retaining wall. Monitoring data shows that the design for the slope engineering has a good effect, and slope retaining structures are stable as a whole during the monitoring period. This research provides reference in design and monitoring for other projects in this area.

Abstract: Based on a deep foundation pit engineering of Tangshan, considering the interaction of pile-anchor-soil, the finite difference software FLAC^3D is adopted in this paper to simulate and analyze the effect of dip angle of anchor and the embedded depth of pile on the horizontal displacement and the variation laws of earth pressure, horizontal displacement of pile with the process of excavation. The results show that the maximum value of horizontal displacement and positive moment of pile appear in 0.85H (H stands for the depth of excavation) and the negative moment appears in 1.3H after the excavation; the maximum value of active and passive earth pressure appear in 1.3H rather than the bottom in the range of pile length; the requirements of deformation control and overall stability of foundation pit can be satisfied with 0.5H which as the embedded depth of the pile, and the dip angle of anchor is appropriate when it ranges from 5°to 25°but less than 30°.

Abstract: An artificial island under construction is located at an open sea and constructed by such a way that island walls are composed of steel cofferdams inserted into impermeable layers and then filled with sands. Grounds on the island are covered by thick soft soil layers with high water content, large compressibility and low bearing capacity, and treated by a jointed dewatering surcharge preloading method. In order to know the settlement property of the soft soil ground, the numerical analysis is implemented. During the analyzing, the parameters are adjusted and calculated through inverse analysis compared with practical measured data. So the numerical calculation results are more reliable. The analysis results indicate that the residual settlement of the soft soil ground is 9cm, and main ground consolidation settlement will be completed for two years after construction finished.

Abstract: The rapid development of deep foundation pit engineering, has become an important part of the urbanization construction, which brings deep excavation support of geotechnical engineering problem research also became a major issue. This paper uses the international well-known geotechnical engineering numerical simulation software FLAC3D, through 3D finite difference numerical calculation and analysis, to better simulation calculation and analysis of deep foundation pit construction site condition, forecast after excavation of the deep foundation pit deformation displacement and dangerous position, analysis of deep foundation pit excavation process isolation pile - steel shotcrete combined support effect. Three dimensional numerical model analysis and calculation in deep foundation pit engineering design and construction scheme optimization with economy is convenient wait for a obvious advantages, can for deep foundation pit excavation of deep foundation pit support design and construction to provide effective basis.