A novel preloading method for foundation underpinning for the remodeling of an existing building

IF 2.5 3区 工程技术 Q2 ENGINEERING, CIVIL
Chengcan Wang, Jin-Tae Han, S. Kim, Y. Jang
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引用次数: 0

Abstract

The utilization of buildings can be improved by extending them vertically. However, the added load of the extension might require building foundations to be underpinned; otherwise, the loads on the foundations might exceed their bearing capacity. In this study, a preloading method was presented aiming at transferring partial loads from existing piles to underpinning piles. A pneumatic-type model preloading device was developed and used to carry out centrifuge experiments to evaluate the load–displacement behavior of piles, the pile–soil interaction during preloading, and the additional loading caused by vertical extension. The results showed that the preloading devices effectively transfer load from existing piles to underpinning piles. In the additional loading test of group piles, the load-sharing ratio of a pile increased with its stiffness. The load-sharing ratio of a preloaded micropile was less than that of a non-preloaded micropile as a result of the reduction in axial stiffness caused by preloading before additional loading. Therefore, a slight reduction of the load-sharing capacity of an underpinning pile should be considered if the preloading method is applied. Further, two full scale preloading devices was developed. The devices preload underpinning piles and thereby produce reaction forces on a reaction frame to jack existing piles upward, thus transferring load from the existing piles to the underpinning piles. Specifically, screw-type and hydraulic-jack type devices were developed for the practical application of foundation underpinning during vertical extension, and their operability and load transfer effect verified via full-scale structural experiments.
一种新的预压方法用于既有建筑的改造基础支撑
通过垂直延伸,可以提高建筑物的利用率。然而,扩建工程增加的负荷可能需要加固建筑物的地基;否则,地基上的荷载可能会超过其承载能力。本研究提出了一种将既有桩的部分荷载传递给托存桩的预压方法。研制了一种气动预压模型装置,并进行了离心试验,对桩的荷载-位移特性、预压过程中桩土相互作用以及竖向延伸引起的附加荷载进行了评价。结果表明,预压装置能有效地将既有桩的荷载传递给托存桩。在群桩附加荷载试验中,桩的荷载分担率随桩刚度的增大而增大。预压微桩的荷载分担比小于未预压微桩,这是由于在附加荷载之前进行预压导致轴向刚度降低所致。因此,如果采用预压方法,应考虑承插桩的荷载分担能力略有降低。此外,还研制了两种全尺寸预压装置。该装置预压支撑桩,从而在反力架上产生反力,使现有桩向上顶起,从而将荷载从现有桩转移到支撑桩上。具体而言,针对垂直延伸过程中基础支撑的实际应用,开发了螺杆式和液压千斤顶式装置,并通过全尺寸结构试验验证了其可操作性和荷载传递效果。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Geomechanics and Engineering
Geomechanics and Engineering ENGINEERING, CIVIL-ENGINEERING, GEOLOGICAL
CiteScore
5.20
自引率
25.00%
发文量
0
审稿时长
>12 weeks
期刊介绍: The Geomechanics and Engineering aims at opening an easy access to the valuable source of information and providing an excellent publication channel for the global community of researchers in the geomechanics and its applications. Typical subjects covered by the journal include: - Analytical, computational, and experimental multiscale and interaction mechanics- Computational and Theoretical Geomechnics- Foundations- Tunneling- Earth Structures- Site Characterization- Soil-Structure Interactions
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