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| Research on the Deformation and Bearing Characteristics of Composite Foundation with Long and Short Piles |
| MA Xue - ning，LI Shan - zhen，TIAN Zhao - bin，WANG Bo - lin |
| (Lanzhou Jiaotong University，Lanzhou，Gansu 730070，China) |
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Abstract Research purposes： Under embankment load， the wolfing mechanism of long and short piles composite ground is very complicated and the research results of the design and calculation are fewer. In order to promote this composite ground，it is necessary to study the behaviors of the composite ground. The settlement characteristics of the long and short piles composite ground are studied with field tests，then the effects of pile length on the settlement and bearing characteristics of composite ground are studied using numerical simulation. The accuracy of the model and the rationality of the parameters are verified through comparing analysis. Research conclusions ：( 1) Under embankment load，the settlement process of long and short piles composite ground is divided into three stages： the rapid development stage in which the settlement is 59. 2% to 62. 5% of the total settlement; the first 45 days in the rest period is the gradual development stage in which the settlement is 28. 1% to 33.3% of the total settlement; the last stage is the stable stage of settlement in which the settlement is about 7. 5% to 9. 45% of the total settlement. (2)The subgrade base settlement along the cross - section has a bowl - like distribution， the largest value is at roadbed centerline， the minimum value is at the foot of the slope; short piles length and substratum stiffness should be considered when the long piles are designed. Meeting the settlement and bearing capacity，the short piles are designed on the basis of the project cost. (3 ) At first the stresses of both long and short piles increase then decrease with the pile depth，the peak appears at a certain depth near the top of the pile. The stresses of long pile decrease with increasing of the short pile length，and the whole pile length play a bearing role. (4) At first the pile soil stress ratio and load sharing ratio of long piles increase rapidly，then tend to stable，and they decrease with the increase of short pile length. (5 ) The research results can provide theoretical basis for the design of composite ground with long and short piles under embankment load.
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Received: 22 July 2015
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2016, Vol. 33 
