Model Experimental Study Of The Combination Of Miniature Steel Pile Structure Working Mechanism

Miniature steel pipe pile, generally refers to pile diameter70~300mm, thedrilling, strong reinforcement, pressure grouting process of the construction of the pile.Early1950s mini piles is by Italian fondedile company first development application,early for foundation reinforcement, continuously in recent years for landslide, slopereinforcement works, but its design theory is not mature, due to the mini pilesmechanism of pile and rock mass is common of the formation of the role of slidingbody to resist the thrusting force, different from the general anti-slide pile, the moredifferent from the upper structure of beam-column elements. In engineering practice,many important parameters is often through the test pile experiment or reference otherengineering experience obtain. So the micro steel pipe piles in supporting function ofthe slope is very necessary.In this paper, the extensive collection of experimental research, theoreticalcalculation data on the basis of their own design of a miniature steel pipe pile compositestructures model test device, and the shape of the soil in the three groups to change thepile spacing, as well as a group to change the pilecarrier damage model test, a series ofmini-steel pipe pile composite structures model test experimental data and to collate andtheoretical calculations, the details and the main results are as follows：(1) According to the horizontal displacement of the top beam, pile the maximumbending moment, the earth pressure in the front row after another process line, the twocharacteristic values of bearing capacity micro pile of anti-slide structure: the criticalload and ultimate load. Critical load corresponds to the level of the top beamdisplacement~load curve inflection point, at this time, the earth pressure have not yetreached the passive limit state, the shaft is flexible working state, the entire structurecan continue to carry; ultimate load, pile extremum bend moment load curve of theinflection point or extreme moment close to the maximum soil pressure reaches thepassive limit state.(2) Keeping other factors constant, the critical load of the sliding structure of themicro-pile by the pile spacing by the pile of clay affect the more significant; micro pileof anti-slide structure ultimate load increased with the pile spacinglarge increase (traitvariation) decreases with the moisture content of soil between piles.(3) In the process of loading, the load distribution of the micro-pile anti-slide structure is change. Anchoring segment moment is the extreme values, generally,behindpile>middle piles> front pile.As the load increased, the difference among the threedecreases gradually, very close to the critical load of the three; by the negative momentof the load segment extremum in critical load, generally, behind pile> middle pile≥before pile.(4) Assuming that the top of the pile connection for a sliding bearing, pile the end ofthe physical and mechanical model of the free and bound, the shaft will be divided intotwo parts by the load segment and the anchoring section, using ground-based coefficientmethod and combined with the knowledge of structural mechanics, mechanics ofmaterials, such as byload segment and the anchoring section of internal forces of changederived into four groups and the specific parameters of the model test to solve, and solvethe internal forces of the results were compared with experimental results, the result ismore consistent.(5) Displacement at pile top and pile stresses to control the ultimate bearing capacityof the composite structure, respectively, are calculated to pile top displacement controlto calculate the ultimate bearing capacity is larger than the actual. Combined with acomprehensive analysis of the experimental phenomenon, given the value of theultimate bearing capacity of the composite structure in the four sets of model tests.