梅花形布桩桩承式路堤土拱效应计算方法的研究

摘要

In this paper,a new calculation method for soil arch effect of piles with quincunx-shape layout is derived and formulas of pile efficacy and pile-soil stress ratio are obtained.The influence of internal friction angle of filling,height of embankment,ratio of pile diameter and pile spacing on vertical stress distribution,pile efficacy and pile-soil stress ratio of pile-supported embankment with square layout and quincunx-shape layout are analyzed.Research results show that pile-supported embankment with square-shape layout is similar to pile embankment with quincunx-shape layout in verti-cal stress changing characteristics.But the height of soil arch with square-shape layout is 13% more than that of soil arch with quincunx-shape layout.The development of soil arch can be divided into undeveloped state,developed state and plastic state.The critical height of soil arch formed in pile-supported embankment with square-shape layout is 0.8 times of net spacing between piles and for quincunx-shape layout,0.7 times of net spacing between piles.The greater the Angle of internal friction of filling is,the smaller of the pile spacing,the higher the critical height of embankment of the soil arch plastic state.If internal friction angle of filling is 25 °~45 °and layout of pile is quincunx,the calculation results with Hewlett's method is 2.6~8.2 % smaller than that with the method in the paper.%推导了梅花形布桩的土拱效应计算方法，得到了桩体荷载分担比和桩土应力比表达式。研究了填料内摩擦角、路堤高度、桩径与桩间距比值对正方形布桩和梅花形布桩路堤竖向应力分布、桩体荷载分担比和桩土应力比的影响。研究表明：正方形布桩和梅花形布桩的路堤竖向应力变化特征相似，但正方形布桩时土拱高度大于梅花形布桩，二者之差约为13％；土拱发展可分成未形成土拱、土拱发育状态及塑性状态3种状态；路堤形成土拱的临界高度正方形布桩时为0.8倍净桩间距，梅花形布桩时为0.7倍净桩间距；填料内摩擦角越大，桩间距越小，土拱塑性状态的路堤临界高度越高。填料内摩擦角为25°～45°，梅花形布桩时，采用Hewlett法计算，结果将比文中提出的计算方法小2.6％～8.2％。