Model Test Research On Pulling-out Failure Mode Of Fully-embedded Anti-slide Pile

Our nation is a mountainous country. With the development and construction ofSouthwest China, more and more economic activities are carried out in mountainousareas, such as road building, mining, and constructions of dams. This will lead to moregeological hazards. Moreover, with the vigorous development of urban trafficengineering and underground construction engineering, the problems of urbanpopulation density and urban land shortage become serious, thus the foundation pitsupporting projects become more important. Anti-slide pile plays a great role inengineering. However, the design theory of anti-slide pile is not perfect, causing seriouswaste phenomena, and sometimes unsafe factors. Therefore, more and more attention ispaid to landslide resistance mechanism. According to the buried situations, anti-slidepile can be divided into the following three categories: cantilevered anti-slide pile,fully-embedded anti-slide pile and sunken anti-slide pile. By contrast with cantileveredanti-slide pile, the other two have a lower bending moment, cost fewer consumables,thus greatly improve the mechanical behavior of anti-slide pile, and reduce theengineering cost. This thesis is mainly to discuss the fully-embedded anti-slide pile.At present the design of anti-slide pile mainly relies on industry standard andengineering experience. However, the calculation assumption for the standard andexperience is too simplified; calculation formula is too complex; designers chooseparameter value at will. In the final analysis, people are unclear about the mechanism ofpile-soil interaction. To investigate the working conditions of anti-slide pile, to evaluatethe safety performance of anti-slide pile regulation project, and to monitor the internalforces, are effective ways to solve such problems. This thesis aims to monitor the steelstrain, the concrete strain, displacement of pile top, and the earth pressure around pilesunder the pulling out failure mode of fully-embedded anti-slide pile, and to study thestress mechanism of fully-embedded anti-slide pile combined with the numericalsimulation results.The main work and research conclusions are as follow:①Experimental researchAn indoor trust-pile test of fully-embedded anti-slide pile, arranging earth pressurecells, steel strain gauge, concrete strain gauge, and dial indicator, is needed to beestablished. In this way, a multi-channel dynamic measuring system of landslide to monitor the strain and displacement of piles and also the earth pressure is established.By the steel strain and concrete strain of the piles, it is proved that when the anchoragedepth is not enough, the rigid rotation of the piles is significant while the strain of thepiles is not obvious. The moment is calculated by the curvature of the pile and the actualsoil pressure, and then the internal force is analyzed.②Theoretical analysisThe mechanism of pile-soil interaction is analyzed, using the measured data by theindoor thrust-pile test, combined with soil arching effect. By the analysis of the workingstate parameters of the pile, it is proved that the both sides of pile are subjected to anupward pulling force, which makes the piles have a trend of pulling-out failure mode.③Numerical simulationThe pulling-out failure mode of anti-slide piles is simulated, using FLAC3D.Themechanism of pile-soil interaction is analyzed, and the distributions of landslide thrustcan be obtained and compared with the test results. By the simulation analysis of themodel test, it is found out that the slide upwelling area has a trend of extending, and thatthe pile body is subjected to a pulling-out effect by soil around piles. By studying thesoil arching effect and its influencing factors, it is found out that the soil arching effecthas some spatial characteristics.The mechanism of pulling-out failure mode of fully-embedded anti-slide pile isstudied. And it has some guiding significance for making the mechanism of pile-soilinteraction clear, the optimization for similar engineering design, and upgrading theengineering’s safety. It is suggested that the real-time monitoring can be applied inexisting projects and a post-evaluation system of the security and economy of anti-slidepiles is needed to be developed, making further perfection of design theories.