粉土地基CFG桩与螺杆桩复合地基承载特性对比分析
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摘要
由于承载力高、造价低等优点,螺杆桩复合地基已在多条高速铁路、客运专线上广泛使用,但独特的变截面设计使得其受力机制和承载特性比普通直杆桩复杂。为研究粉土地基中螺杆桩的承载特性,以呼和浩特至准格尔新建铁路工程为背景,采用室内模型试验,对比分析螺杆桩和直杆桩的单桩及单桩复合地基承载特性。研究结果表明:在相同桩径和桩长条件下,螺杆桩单桩极限承载力比直杆桩单桩提高67%;螺杆桩单桩复合地基极限承载力比直杆桩单桩复合地基提高43%;螺杆桩的轴力在直杆与螺杆段的交界处出现明显拐点。直杆桩复合地基顶部存在负摩阻区,螺杆桩复合地基在直杆与螺杆段的交界点下方约30 cm处出现了负摩阻区,在工程设计、施工中,应注意变截面处的处理,以防止负摩阻力作用对桩体结构的破坏。
With its advantages of high bearing capacity and low cost, screw pile composite foundation has been widely applied in many high-speed railways and passenger dedicated lines. However, its distinctive design with variable cross-section causes more complex stress mechanism and bearing behavior of screw pile than those of common straight pile. In order to analyze the bearing behaviors of screw pile in silt soil foundation, an indoor model test was carried out to compare the bearing characteristics of single pile and single pile composite foundation of straight pile and screw pile based on Hohhot-Zhungeer Railway, the national key construction railway project. The results show that under the same condition of pile diameter and pile length, the ultimate bearing capacity of single pile composite foundation of screw pile is improved by 43% compared with that of straight pile, and the ultimate bearing capacity of single pile of screw pile is increased by 67% compared with that of straight pile. The screw pile shows a significant turning point at the juncture of straight and screw section in the distribution of axial force. A negative frictional resistance area exists at the top of the straight pile composite foundation. A negative friction area appears below the junction of straight section and screw section in the screw pile composite foundation, which should receive attention to the treatment of variable cross-section in the process of engineering design and construction to prevent the destruction of negative friction on pile structure.
With its advantages of high bearing capacity and low cost, screw pile composite foundation has been widely applied in many high-speed railways and passenger dedicated lines. However, its distinctive design with variable cross-section causes more complex stress mechanism and bearing behavior of screw pile than those of common straight pile. In order to analyze the bearing behaviors of screw pile in silt soil foundation, an indoor model test was carried out to compare the bearing characteristics of single pile and single pile composite foundation of straight pile and screw pile based on Hohhot-Zhungeer Railway, the national key construction railway project. The results show that under the same condition of pile diameter and pile length, the ultimate bearing capacity of single pile composite foundation of screw pile is improved by 43% compared with that of straight pile, and the ultimate bearing capacity of single pile of screw pile is increased by 67% compared with that of straight pile. The screw pile shows a significant turning point at the juncture of straight and screw section in the distribution of axial force. A negative frictional resistance area exists at the top of the straight pile composite foundation. A negative friction area appears below the junction of straight section and screw section in the screw pile composite foundation, which should receive attention to the treatment of variable cross-section in the process of engineering design and construction to prevent the destruction of negative friction on pile structure.
引文
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[3] 刘志明.深厚填土地基螺杆桩加固处理应用研究[J].资源环境与工程,2015,29(3):323-326.LIU Zhiming.Application Research of Screw Pile in Dee PFill Foundation Reinforcement[J].Resources Environment& Engineering,2015,29(3):323-326.
[4] 万鹏洲.螺杆桩在盐渍土地区铁路地基处理中的施工关键技术与承载特性分析[J].铁道建筑技术,2016(5):82-86.WAN Pengzhou.Key Construction Techniques and Bearing Behaviors of Railway Foundation Treatment with Screw Pile in Saline Soil Area[J].Railway Construction Technology,2016(5):82-86.
[5] 张伟,彭振斌,李志平.螺杆桩在地基处理中的应用[J].岩土工程界,2007(11):38-39.
[6] 方崇,张信贵,彭桂皎.对新型螺杆灌注桩的受力特征与破坏性状的探讨[J].岩土工程技术,2006(6):316-319.FANG Chong,ZHANG Xingui,PENG Guijiao.Discussion on the Bearing Force Characteristic and the Failure Behavior of a New Kind Half-screwed Filling Pile[J].Geotechnical Engineering Technique,2006(6):316-319.
[7] 彭奎森.竖向荷载作用下螺杆桩受力特性分析研究[D].湘潭:湘潭大学,2010.
[8] 徐梁.螺杆桩承载特性分析与试验研究[D].合肥:合肥工业大学,2013.
[9] 栾光日,王连俊,李懿,等.高速铁路站场宽路堤复合地基沉降特性分析[J].铁道学报,2014,36(10):95-101.LUAN Guangri,WANG Lianjun,LI Yi,et al.Research on Settlement Characteristics of Wide Embankment Composite Foundation of High-speed Railway Stations[J].Journal of the China Railway Society,2014,36(10):95-101.
[10] 张继文,曾俊铖,涂永明,等.京沪高速铁路CFG 桩-筏复合地基现场试验研究[J].铁道学报,2011,33(1):83-88.ZHANG Jiwen,ZENG Juncheng,TU Yongming,et al.Experimental Study on CFG Pile-raft Composite Foundation of Beijing-Shanghai High-speed Railway[J].Journal of the China Railway Society,2011,33(1):83-88.
[11] 曾俊铖,张继文,童小东,等.高速铁路CFG桩复合地基应力特性试验研究[J].铁道学报,2011,33(5):91-96.ZENG Juncheng,ZHANG Jiwen,TONG Xiaodong,et al.In-situ Test of Stress Characteristics of CFG Pile Composite Foundation of High-speed Railway[J].Journal of the China Railway Society,2011,33(5):91-96.
[12] 罗大生,肖超,张可能,等.南沙地区钉形水泥土搅拌桩荷载传递规律的试验研究[J].中南大学学报(自然科学版),2012,43(9):3575-3581.LUO Dasheng,XIAO Chao,ZHANG Keneng,et al.Load Transfer Mechanism of T-shaped Soil-cement Deep Mixing Pile in Nansha Area,Guangzhou[J].Journal of Central South University (Science and Technology) ,2012,43(9):3575-3581.
[13] 周景星,李广信,虞石民,等.基础工程[M].2版.北京:清华大学出版社,2007.