\r冯忠居¹，董芸秀^{1, 2}，文军强¹，胡海波¹，李孝雄³，何静斌\r¹\r
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AuthorsHTML:\r冯忠居¹，董芸秀^{1, 2}，文军强¹，胡海波¹，李孝雄³，何静斌\r¹\r
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AuthorsListE:\rFeng Zhongju¹，Dong Yunxiu^{1, 2}，Wen Junqiang¹，Hu Haibo¹，Li Xiaoxiong³，He Jingbin\r¹\r
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AuthorsHTMLE:\rFeng Zhongju¹，Dong Yunxiu^{1, 2}，Wen Junqiang¹，Hu Haibo¹，Li Xiaoxiong³，He Jingbin\r¹\r
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Unit:\r\r1. 长安大学公路学院，西安 710064；\r
\r\r2. 陇东学院土木工程学院，庆阳 745000；
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\r3. 滁州学院地理信息与旅游学院，滁州 239000\r
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Unit_EngLish:\r1.School of Highway，Chang’an University，Xi’an 710064，China；
2. School of Civil Engineering，Longdong University，Qingyang 745000，China；
3. School of Geographic Information and Tourism，Chuzhou University，Chuzhou 239000，China\r
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Abstract_Chinese:\r深厚软基路桥过渡段处理不当而引发的问题逐渐突显，为从设计优化角度解决深厚软基区路桥差异沉降变形问题，基于宁波市北仓区静载荷试验实测的7 根桩基础的P-s 曲线，分析了宁波深厚软基区桥梁桩基础的承载特性；通过数值模拟，建立了不同软土厚度下桩基础的三维有限元模型，研究了深厚软基区桥梁桩基础穿越软土层和未穿越软土层时的承载性能；采用回归分析法，分别以桩顶位移控制量40 mm、60 mm 建立了深厚软基区桥梁桩基础穿越软土层和未穿越软土层时的承载力计算公式．研究结果表明：桩基P-s 曲线呈缓变型，无明显向下转折段．桩顶沉降最大达到49.6 mm，任一级沉降均未超过上级沉降的5 倍，深厚软基区的桥梁桩基存在设计承载力安全储备过大的问题；当桩穿越软土层时，桩承载力随软土层厚度增加呈线性减小，桩未穿越软土层时，软土厚度对桩承载力影响不明显，桩长30 m 的桩基承载力在软土厚度为30 m 时出现明显的分界点；根据静载试验和有限元模拟结果，回归建立了桩顶位移控制量40 mm、60 mm 时桩的承载力公式，并通过工程实例验证了公式的可行性；提出了深厚软基区公路桥梁的桩长优化公式及其适用条件，并给出了深厚软基区公路桥梁桩长折减系数α 取值表．\r
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Abstract_English:\rThe problems caused by the improper treatment of the transition section of deep-soft-subgrade bridges have become increasingly obvious．From the perspective of design optimization，to solve the differential settlement deformation of roads and bridges in deep soft foundation areas，we analyzed the bearing characteristics of seven bridge pile foundations in the deep soft foundation areas of the Beicang district in the city of Ningbo based on their P-s curves，as measured in static load tests．We constructed a three-dimensional numerical model of a pile foundation with different soft-soil-layer thicknesses，and investigated the bearing capacities of pile foundations that do and do not pass through soft soil layer in a deep soft soil area．Using regression analysis，we derived bearing capacity formulas for pile foundations that do and do not pass through a soft soil layer for 40-mm and 60-mm displacements of the pile top．The results show that the P-s curves of pile foundations in deep soft soil areas are mostly the slow type with no downturn section．In our tests，the settlement of the pile top reached a maximum of 49.6 mm，and the settlement
of any level did not exceed five times the settlement of the previous level．Based on our results，we conclude that the current safety reserve of the designed bearing capacity of a bridge pile foundation in deep soft areas is too large．When the pile crosses through the soft soil layer，the bearing capacity of the pile increases linearly with the thickness of the soft soil，but the thickness of the soft soil layer exhibits less effect on the bearing capacity when the pile does not go through the soft soil layer．The bearing capacity of pile foundations with a pile length of 30 m appears to have an obvious cut-off point when the soft soil thickness is 30 m．Based on the results of a static load test and numerical simulations，we used regression analysis to establish a pile bearing-capacity formula for pile top displacements that are more that 40 mm and 60 mm，and we verified the feasibility of this formula using engineering examples．As such，we propose an optimization formula for pile length and its applicable conditions，and provide the calculation formula for pile-length reduction coefficient α，which can be used for reference．\r
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Keyword_Chinese:岩土工程；深厚软基；桩基承载力；桩顶位移控制量；桩长优化\r

Keywords_English:geotechnical engineering；deep soft base；bearing capacity of pile foundation；pile top displacement control；pile length optimization.\r


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