Research on the Optimum Design of Pile-Plank Embankment’s Parameters in the Collapsed Loess Ground
|School||Lanzhou Jiaotong University|
|Course||Road and Railway Engineering|
|Keywords||Pile-Plank Embankement Expensive Soil Orthogonal Experiment Finit Element Optimum Design|
Pile-plank embankment is a kind of new-type form of ballastless truck in high-speedrailway, it is composed with the reinforced concrete plank at its upside and reinforcedconcrete piles, subgrade and subground at its downside. It synthesizes respectivecharacteristic with the ballastless truck and the piles, possessing the advantages of higherentirety and stability, greater durability, lower strain and less settlement, more convenient forconstruction, less maintenance and repair, etc. Therefore the piled-plank embankments arequite valuable to be extending in modern domestic and foreign railroads and highwayconstruction. So far, the application of pile-plank embankment just starts in China, with nodesign code, and the pile-plank embankment is only restricted in the soft soil ground and thecollapsible loess ground in domestic projects application and fundamental research, not yetpromoted to expensive soil ground processing project. In view of the prominent merit ofpile-plank embankment, this article will attempt to use it in expensive soil.In this paper, the application of the finite element analysis software ANSYS, establishthe finite element of collapsible loess foundation subgrade pile-slab structure model, pile slabstructure subgrade bottom in wet Subsidence Loess Layer and pile bottom at the bedrocklayer were calculated, analyzed two kinds of circumstances, the pile-plank structure roadbedsoil characteristics and their settlement the. For the two cases of settlement in their respectivecharacteristics, the collapsible loess area design proposals pile slab structure subgrade, designprovides a basis for the follow-up research and collapsible loess pile slab structure subgrade.On the basis of the pile-plank structure roadbed design theory research at home andabroad, this paper studies the structural mechanics of pile-plank subgrade-board features,according to the engineering characteristics of collapsible loess, analysis of the stresscharacteristics of collapsible loess pile slab structure subgrade. On this basis, puts forward thedesign method of collapsible loess area of pile-plank structure roadbed, the collapsible loesspile slab structure subgrade control indicators and limits.Finally, Zheng–Xi railway Line forpassengers，using the orthogonal experimental designmethod, combined with the technical and economic index, design parameters of collapsibleloess area of pile-plank structure roadbed were optimized, the reasonable value range of thedesign parameters, obtained the following conclusions.（1） according to the collapsible loess foundation pile slab structure subgrade finiteelement model, the bottom of pile in collapsible loess layer and pile bottom at the bedrocklayer are calculated for the two cases analysis, calculation and analysis of settlement deformation of subgrade and pile side soil, and settlement characteristics of two cases analysis,proposed the pile-plank structure in collapsible loess ground, settlement control from thecollapsible loess subgrade pile-slab structure design（2） to carry on the system analysis to calculation method and design theory ofcollapsible loess subgrade pile plate structure. And the analysis of pile slab structure Subgradein collapsible loess in the stress characteristics, and puts forward the pile-plank structureroadbed in specific checking project in collapsible loess area and calculation method ofdesign, and the deflection and crack, settlement control index values were calculated. For thepile slab structure Subgrade in collapsible loess region provide reference（3）after the analysis, the influence of vertical span on the maximum bending momentis very large. With the increase of span, the maximum bending moment is increasingconstantly, and the rate of increase of changing rapidly, there is an inverse relationshipbetween the. If the larger span, span will result in reduced the maximum bending momentdecreased significantly; if small span, span decrease the maximum bending moment decreaseslittle effect.（4） Analysis of software ANSYS, the influence value settlement of pile slab structuresubgrade caused by the design parameters of the pile-plank structure roadbed. The diameter ofthe pile is an important parameter to affect the design of pile-plank structure roadbedsettlement. To reduce the subgrade settlement can be increased to pile diameter. Settlement ofpile slab structure subgrade and pile diameter is inversely proportional, showing a non-linearrelationship. In case of small diameter of pile, pile diameter increases obviously on thesettlement decreases; in a large pile diameter, pile diameter does not increase significantly onsettlement reduction effect. Obvious impact on the pile settlement size area of about0.8m-1.2m, starting from the angle of settlement control, pile diameter design should choosebetween economic and rational0.8m-1.2m.（5）the effect of economic technology index, according to the rule of the designparameters of the pile-plank structure roadbed, summarizes the technical economic index,gives the background of Zhengzhou-Xi’an Passenger Dedicated Line Engineering, collapsiblereasonable value of design parameters of the interval of pile-plank structure roadbed loessarea, provide a reference foundation in collapsible loess area promotion application as the pileplate structure, the reasonable range of span:5~9m; reasonable interval thickness:0.6~1.2m;the diameter of pile reasonable interval:0.8~1.2m.