| Landslide is a one of the common geological hazards all over the world. It is an adverse geological phenomenon occurring when a mountain overall slides along the weak plane or soft belt under the effect of gravity, such as ground movement. China is a geological hazards-prone country where the landslide is the most widely spread and most harmful one in the mountainous areas. Although the world’s economic develops rapidly in the recent100years especially after the Second World War, the casualties and economic losses are also increasing rapidly caused by landslide disasters. As the construction of the Three Gorges Dam is completed, collapse and landslides caused by the impoundment of the Three Gorges reservoir are the main types of geological hazards in the Three Gorges reservoir. Landslide geological hazards has posed severe threats to people’s life and property security, thus the government invest a lot of money each year into the prevention and research work of geological hazards. In order to avoid or reduce landslide geological hazards, and ensure the safety of people’s life and property, it is urgent to conduct the theoretical research on the prevention and treatment of landslide to provide scientific theoretical basis for engineering practice.Anti-slide piles have been widely used as an effective means against landslide in the fact that they have strong ability against sliding, satisfactory retaining effect, causing little disturbance to the sliding body, and the advantages of flexible pile position, safe and convenient construction. At present, although the theory of anti-slide pile design has made great progress, it lags severely behind the engineering practice. Engineering cases of the friction pile adopted in landslide control are for the most part successful, but many of them are the results of conservative design. While some failure cases highlight the disadvantages of subjective experience in the design of the anti-slide pile, for example, the selection of anti-slide pile design parameters is with great randomness, lack of scientific theoretical basis, so it is difficult to achieve a win-win ending of security and economy.Considering the weakness of present anti-slide piles cross section forms which is limited to rectangle and circle, the writer makes a research of the anti-slide pile section based on the theory of traditional anti-slide pile design in this paper, where nonrectangular cross-section pile was explored, such as the isosceles trapezoid section pile. The interaction mechanism of the cantilever anti-slide pile and the landslide body was studied and some fundamental rules were found so as to realize the full play of the soil arch effect. A best collaborative work model of isosceles trapezoid section pile and the landslide was built, providing a theoretical support for anti-slide pile section size optimization. This research will facilitate the achievement of the best effect of anti-sliding piles and help save engineering funds to the maximum extent on the premise of the safety of landslide, which is a win-win result for security and economy. The research results are of important theoretical significance and wide engineering application prospects that can serve as a scientific theoretical foundation for ant-slide control engineering and the design of anti-slide pile.Main content includes the following several aspects:(1) A cantilever beam model in Material Mechanics is adopted for the theoretical derivation. According to different distribution mode of landslide thrust force, anti-slide pile displacement along its height and above the corresponding sliding surface was deduced under the action of landslide thrust force. A corresponding theoretical formula of the deflection of anti-slide pile top was also deduced. They have very important theoretical significance and engineering application value to the design of the anti-slide pile and the evaluation of landslide treatment effect.(2) Through mechanics analysis and combined with numerical simulation inversion analysis put forward a concrete method of calculating the composite modulus of elasticity.(3) According to the interaction of piles and soil, pile spacing calculation models were established for the minimum pile spacing considering the arch effect of the back soil of the pile and the maximum pile spacing considering the arch effect of the lateral soil between piles. Furthermore, based on the traditional two-level load transfer model of the anti-slide pile and landslide body, a3-level load transfer model of "end bearing soil arch","friction soil arch, and pile front soil was introduced, which more deeply reveals the force transfer mechanism of anti-slide pile in effect.(4) In order to understand more clearly the soil arch effect of pile and soil interaction, an isosceles trapezoid section pile different from rectangular cross section was introduced. And with the aid of the numerical simulation software FLAC3D, numerical models of the isosceles trapezoid pile, rectangle and isosceles were set up, respectively. Two-level load transfer model was analyzed of the back and the lateral soil arch effect for different cross section shape of anti-slide piles, the main research results are as follows:①Under the effect of landslide thrust force, the connection of the maximum principal stress behind the piles is arched, indicating soil arch is formed behind the piles. There is no obvious soil arching effect within a distance of4b behind the piles.②The load transferred from soil to the piles increase in the order of isosceles trapezoid pile, rectangle and isosceles trapezoid outside piles, suggesting a more and more significant effect of the piles.③Anti-slide piles assume a typical two-level soil arch load transfer pattern under the landslide thrust force, where back soil arch plays a main role and lateral soil arch plays a secondary effect. Isosceles trapezoid anti-slide pile can give full play to back soil arch effect, while an isosceles trapezoid anti-slide pile can fully fulfill the lateral soil arch effect.④As a result of the existence of anti-slide pile, displacement around the pile is smaller. Displacement of landslide soil is the largest for the rectangle pile, followed by the isosceles trapezoid pile, and the smallest for the isosceles trapezoid.⑤For inner-isosceles trapezoid cross-section pile, in a certain range of pile spacing, the back soil carries a bigger and bigger load share ratio with the increase of pile spacing, but load rate began to fall when pile spacing reaches a certain value. For rectangular cross-section pile and outer-isosceles trapezoid cross-section pile, the back soil arch shares a decline load with the increase of pile spacing, but declines slightly when the pile spacing increases to a certain value.⑥As for inner-isosceles trapezoid cross-section pile, with the increase of pile spacing, the lateral soil arch share a smaller and smaller load ratio, but the downward trend line slope is smaller and smaller. In general, the lateral soil arch for the isosceles trapezoid has a relatively large load sharing ratio. For rectangular cross-section pile and outer-isosceles trapezoid cross-section pile, with the increase of pile spacing, the lateral soil arch shares an increasing load ratio. However, the soil arch load share ratio between piles is generally small for rectangular pile and outside isosceles trapezoid pile.⑦For inner-isosceles trapezoid cross-section pile, under the effect of landslide thrust, experience the landslide chocking, been arch so as to make the pile and the soil arch between piles are able to effectively play a role, along with the rising of the isosceles tfapezoid slope pile been arch effect strengthen, the soil arch between piles at this time also can have can give full play to its effect, which can give full play to the pile been arch arch synergy between pile and soil, its overall anti-sliding effect is the best... |
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