低裙式吸力桩负压沉贯及其抗拔承载力试验研究

发布时间：2018-07-04 06:28

本文选题：低裙式吸力桩 + 超低位真空预压法　；参考：《天津城建大学》2017年硕士论文

【摘要】：为了提高裙式吸力桩的承载力,本文在考虑“土塞”效应的基础上,提出了一种新型低裙式吸力桩模型,使其更易于沉贯且能更好地保护主桶周围土体免受洋流刨蚀。为了验证新型低裙式吸力桩模型的合理性,分别制作了传统单桶式吸力桩模型、普通裙式吸力桩模型与本文提出的新型低裙式吸力桩模型做对比试验。为了模拟海洋土体,本文提出了一种快速固结土体的方法——超低位真空预压法。该方法能够快速固结土体,明显缩短固结时间。采用该方法加固的土体,能够较好地模拟海洋地基土,其强度沿深度方向增加。通过SEM图像及渗透性分析,得出该土体的物性指标及渗流稳定性良好。然后采用抽真空的方式在水下沉贯各类模型桩,并采用双桶负压法沉贯裙式吸力桩模型,验证低裙式吸力桩模型的可行性。试验结果表明双桶负压法能有效减小“土塞”高度,对试验所得数据进行拟合,得出了更加适用于本试验条件的沉贯阻力公式。随后,结合实际工程中吸力桩受力工况,采用本文提出的立面内多角度拉拔试验装置对吸力桩模型进行45°斜拉拔试验,为了相互验证吸力桩的承载力,又采用PLAXIS 3D有限元分析软件对拉拔试验进行模拟,证明了低裙式吸力桩的合理性。最终得到以下主要结论:(1)采用抽真空法沉贯吸力桩,“土塞”现象不可避免;(2)低裙式吸力桩模型的可贯性优于普通裙式吸力桩模型;(3)本文提出的新型低裙式吸力桩模型可有效减小“土塞”高度;(4)拟合出的吸力桩模型沉贯阻力适用于强度沿深度方向增加的土体,更接近于实际工程;(5)新型低裙式吸力桩模型45°抗拔承载能力优于传统单桶式吸力桩及普通裙式吸力桩模型;(6)本文模拟得到的吸力桩抗拔承载力——桩体斜位移曲线与室内模型试验结果吻合度较高,相互验证了试验及数值模拟的合理性。
[Abstract]:In order to improve the bearing capacity of skirt suction pile, a new model of low skirt suction pile is proposed on the basis of considering the "soil plug" effect, which makes it easier to sink and can better protect the soil around the main bucket from ocean current planing. In order to verify the rationality of the new low skirt suction pile model, the traditional single bucket suction pile model, the ordinary skirt suction pile model and the new low skirt suction pile model proposed in this paper are compared with each other. In order to simulate the marine soil, a method of rapid consolidation of soil is presented in this paper, which is the ultra-low vacuum preloading method. This method can rapidly consolidate the soil and shorten the consolidation time. The strength of the soil reinforced by this method can be simulated well and its strength increases along the depth. Through SEM image and permeability analysis, the physical property index and seepage stability of the soil are obtained. Then the vacuum method is used to sink all kinds of model piles under water, and the double bucket negative pressure sinking skirt suction pile model is used to verify the feasibility of the low skirt suction pile model. The test results show that the double-barrel negative pressure method can effectively reduce the height of the "soil plug". The experimental data are fitted and the sinking resistance formula is obtained, which is more suitable for this test condition. Then, combined with the load condition of suction pile in the actual engineering, the suction pile model was tested with the multi-angle drawing test device proposed in this paper in order to verify the bearing capacity of the suction pile. The drawing test was simulated by PLAXIS 3D finite element analysis software, and the rationality of low skirt suction pile was proved. The main conclusions are as follows: (1) the suction pile is sunk by vacuum pumping method. The phenomenon of "soil plug" is inevitable; (2) the penetration of low skirt suction pile model is better than that of ordinary skirt suction pile model; (3) the new low skirt suction pile model proposed in this paper can effectively reduce the height of "soil plug"; (4) the fitted suction pile model can be obtained. Type I penetration resistance is applicable to soils whose strength increases in the direction of depth. (5) the 45 掳uplift bearing capacity of the new type of low skirt suction pile model is better than that of the traditional single bucket suction pile and the ordinary skirt suction pile model. (6) the uplift bearing capacity of the suction pile obtained in this paper is the inclined displacement curve of the pile body. The results of the line and the indoor model test are in good agreement with each other. The rationality of the test and numerical simulation is verified by each other.
【学位授予单位】：天津城建大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU473.1

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