【作者】 袁胜强；

【导师】 雷卫东； 苏栋；

【作者基本信息】 哈尔滨工业大学 ， 土木工程， 2010， 硕士

【摘要】 目前,国内外对水平受荷单桩的研究大多集中在单向加载。而在实际工程中,单桩往往受到多方向水平荷载的作用,例如在地震作用、波浪的冲击下桩基础受到的多方向水平荷载。对于群桩的研究也存在同样的问题,并且水平单向荷载的作用方向一般沿着群桩水平布置的对称轴方向。因此,需要对桩基础在多向荷载作用下和群桩在非对称轴方向的水平单向荷载作用下的特性进行研究。本文首先通过室内三轴试验数据率定出砂土本构模型的主要参数,然后利用数值模拟的手段对水平单向加载、水平多向加载和沿非对称轴方向单向加载作用下砂土中的桩基础进行了研究。首先,对单向和多向荷载作用下的单桩进行了模拟,其中多向加载采用圆及椭圆形的加载路径,几种加载路径中,沿着X方向的最大位移都为10mm。通过模拟发现,单向加载的最大水平力为273N,圆形加载(即X向和Y向的最大位移比为1:1)X方向的最大水平力为255N,和单向加载比较明显减小了。两种椭圆加载(即X向和Y向的最大位移比分别为1:0.6和1:0.2)X方向的最大水平力分别为262N和270N。从以上结果可以看出,在多向加载条件下,X方向的最大水平力明显减少,并且折减的程度随着Y方向的运动位移的增大而增大。然后,对单向荷载作用下的群桩进行了模拟。采用了2×2的群桩布置形式,桩间距为3D(即3倍的桩径)。在单向荷载作用下,前排桩的最大水平力为598N,后排桩的最大水平力为488N。前排桩和后排桩的水平群桩效应系数分别为0.82、0.67。对群桩沿非对称轴方向单向加载的模拟中,沿与X轴夹角为15°和30°的非对称轴方向单向加载时,各桩的桩头水平力的方向始终和位移方向不在同一直线上,当位移为10mm时:位移方向为15°时,桩1、桩2、桩3和桩4桩头水平力的方向分别为16.8°、12.5°、17.6°和11.6°;位移方向为30°时,桩1、桩2、桩3和桩4桩头水平力的方向分别为31.0°、28.7°、31.3°和28.0°。力和位移的方向明显出现了非共轴现象。沿着非对称轴方向加载和对称方向的单向加载的群桩的水平力的合力是不变的,说明加载方向对群桩的总的水平承载力的影响是很微弱的。最后,对多向加载作用下的群桩进行了模拟,和单桩相似,群桩中的各桩的最大水平力都出现了不同程度的折减。并且由于水平群桩效应的影响,各桩最大水平力的折减程度要比单桩大。更多还原

【Abstract】 The present studies on lateral loaded piles were mostly focused on unidirectional horizontal loading. The horizontal forces in practical problems, such as earthquake loading and wave loading, have multidirectional characteristics. The same problems also exist in the pile groups, and the direction of unidirectional horizontal loading is along the symmetry axis of the pile level layout. It is necessary to carry out the study on pile foundation under multidirectional loading, as well as the pile groups under the unidirectional horizontal loading along the asymmetry axis. In this paper, the numerical simulation method is used to study the pile foundation under unidirectional horizontal loading, multidirectional horizontal loading and unidirectional horizontal loading along asymmetric axis direction. The main parameters of numerical simulation were obtained from the triaxial test.First, the single pile under unidirectional and multidirectional horizontal loading was simulated . The simulation of multidirectional horizontal loading took circular (elliptical) path load method. The displacement along X direction is 10mm, the maximum unidirectional horizontal force is 273N, the maximum horizontal force of circular loading (the maximum displacement ratio of X and Y is 1:1) on X direction was 255N. The maximum horizontal force of elliptical loading (the maximum displacement ratio of X and Y are 1:0.6 and 1:0.2)on X direction are 262N and 270N.It can be evidently seen, under multidirectional loading conditions, the maximum horizontal force on X direction has been reduced remarkably, and the reduction degree increased as the Y direction displacement increasing.Then, the pile groups under unidirectional horizontal loading were simulated. The pile layout of 2x2 was used and the piles spacing was 3D (D is the pile diameter). Under unidirectional horizontal loading, the maximum horizontal force of the front row pile is 598N, the maximum horizontal force of the rear row pile is 488N. This indicated generate the horizontal pile group effect.The pile group effect coefficient of the front row pile and the rear row pile are 0.82 and 0.67 respectively. The pile groups under the load along non-symmetry axis direction were simulated. Under unidirectional horizontal loading along the non-symmetry axis direction with the X-axis angle of 15°and 30°, the horizontal force direction of the pile head and displacement direction is non-coaxial. when the displacement is 10mm and the angle of displacement direction is 15°, the angle of he horizontal force direction of pile 1, pile 2, pile 3 and pile 4 are 16.8°, 12.5°, 17.6°and 11.6°; if the angle of displacement direction is 30°, the angle of the horizontal force direction of pile 1, pile 2, pile 3 and pile 4 are 31.0°, 28.7°, 31.3°and 28.0°. The phenomenon of non-coaxial has obviously seen from the direction of force and displacement. The total level force of the unidirectional loading of non-symmetry axis and symmetry direction is unchange, it indicated that the direction of loading did not affect the total horizontal bearing very muchFinally, the pile groups under multidirectional horizontal loading were simulated. The same as single pile, the maximum horizontal force of the pile has suffered reduction of different degree . Because the horizontal pile group effect, the maximum horizontal force of pile reduced more than that of single pile.更多还原