工程地质学报  2017, Vol. 25 Issue (6): 1593-1602   (4338 KB)
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① 福州大学岩土工程研究所 福州 350108;
② 福州大学图书馆 福州 350108

ANALYSIS OF DESIGN ELEMENTS OF INCLINE LOAD SHORT RIGID PILE IN SLOPE CREST ZONE
CHEN Linjing, ZHENG Jun, YU Qifeng
① Institute of Geotechnical Engineering, Fuzhou University, Fuzhou 350108;
② Library of Fuzhou University, Fuzhou 350108
Abstract: The short rigid piles are located on the top of slope and subjected to the incline load. Both the cross effects produced by horizontal and vertical loads and the effect of the slope are needed to be considered in the design. Because of several factors interacting each other, far more complex than that of piles installed in horizontal ground. This paper adopts three-dimensional finite element software and carries out numerical simulation analysis of composite piles by taking into account of many factors. The study finds that under the same load and with the increase of the angle of the composite load, the ultimate bearing capacity firstly decreases and then increases. The influence of the vertical load on the horizontal displacement of the pile is greater than that of the internal force. Increasing the pressure of soil around piles will lead to the promotion of pile displacement and internal force. With increasing of edge distance from the slope crest, the effect will decrease.
Key words: Top surface of pile    Incline load    Influence factors    Numerical simulation

0 引言

1 模型建立

1.1 工程概况

 图 1 坡顶桩模型几何图 Fig. 1 The slope pile geometry model

1.2 三维数值有限元模型建立

δ=tan-1(sinφ×cosφ/(1+sin2φ))0

1.3 模型参数

1.4 边界条件
1.4.1 水平地面

 图 2 有限元网格 Fig. 2 Finite element meshes a.水平地面有限元模型；b.倾斜坡顶面有限元模型

1.4.2 倾斜坡顶面

2 模拟结果分析
2.1 边坡对复合受荷桩承载力影响分析

2.1.1 极限承载力

 图 3 基桩承载力分析图 Fig. 3 Bearing capacity of pile foundation a.水平地面基桩承载力分析；b.坡顶面基桩承载力分析

2.1.2 桩身弯矩及水平位移

 图 4 桩身位移弯矩对比图 Fig. 4 Comparison of pile displacement and bending moment a.桩身弯矩；b.桩身水平位移

2.2 坡顶复合荷载对桩身性状影响分析

2.2.1 单独水平荷载作用

 图 5 水平荷载单独作用下桩身水平位移和内力分布 Fig. 5 Horizontal displacement and internal force distribution of pile under horizontal load a.桩身水平位移；b.桩身弯矩；c.桩身剪力；d.桩身轴力

2.2.2 轴横向荷载共同作用

 图 6 复合荷载作用下桩身水平位移和内力分布 Fig. 6 Horizontal displacement and internal force distribution of pile under inclined load a.桩身水平位移；b.桩身弯矩；c.桩身剪力；d.桩身轴力

2.3 土压力对桩身水平位移和内力的影响

 图 7 土压力对桩身水平位移及内力影响图 Fig. 7 Influence of soil pressure on pile body horizontal displacement and internal force a.桩身水平位移；b.桩身弯矩；c.桩身剪力；d.桩身轴力

2.4 临坡距对桩身水平位移及内力的影响

 图 8 临坡距对桩身位移及内力影响图 Fig. 8 Effect of edge distance from the slope crest on pile displacement and internal force a.桩身位移；b.桩身弯矩；c.桩身剪力；d.桩身轴力

 图 9 桩-土等效塑性应变位移等值云图 Fig. 9 Equivalent plastic strain displacement nephogram of pile-soil a.未加固位移云图；b. B=4d位移云图

3 结论

(1) 坡顶复合受荷桩较水平地面复合受荷桩而言桩身极限承载力有一定程度的减小，且随荷载加载角度的变化较为显著，与水平地面桩相比，坡顶复合受荷桩极限承载力随加载角度增加呈先减小后增大的规律；边坡的存在使桩身位移大幅增加，但其对桩身弯矩的影响较小，且其影响作用随荷载加载角度的增大逐渐减小。

(2) 复合荷载作用下的竖向分力将使桩身水平位移大幅增加，其对桩身内力的影响呈相同规律，但对桩身水平位移的影响作用远大于其对桩身内力的影响。

(3) 坡顶桩周土压力的存在对桩身内力及位移有很明显的影响，且随土压力增大桩身水平位移有显著增加，其最大弯矩和剪力产生的位置均逐渐上移，桩弯矩最大值略有减小。但其影响主要体现在水平位移方面，故实际工程中应注意堆载对结构稳定性的影响。

(4) 临坡距的影响主要体现在桩长范围是否贯穿滑动面，只有贯穿滑动面时才能使桩的抗滑作用得到充分发挥，当穿过滑动面后，临坡距的大小对桩身性状影响较小，但随临坡距增大总体呈现出与水平地面桩靠近的趋势；工程实例中应将临坡距与桩长相结合考虑，在保证抗滑作用发挥的同时应使临坡距最小化。

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