边坡深部不均匀沉降条件下桩基础破坏特性的离心模型试验研究

Centrifuge Model Tests on the Failure Behavior of Pile Foundation Under the Condition of Deep Non-uniform Settlement in Soil Slopes

中国地质条件复杂,岩土工程问题复杂多变。随着工程建设开展,深部不均匀沉降条件下(如:地下煤炭开采、基坑开挖、地下水位变化等),上覆边坡及其上的基础容易发生严重的变形乃至破坏。桩基础是目前工程中常用的边坡加固方式,因此,边坡深部不均匀沉降条件下的桩基础破坏特性亟待研究。作者采用液压系统模拟深部不均匀沉降条件,进行不同范围的深部不均匀沉降条件下桩基础破坏特性的离心模型试验,探究不均匀沉降范围对桩基础变形破坏特性的影响机制,以及深部不均匀沉降条件下桩基础的破坏机理。研究结果表明:1)深部不均匀沉降条件下,桩基础所在土坡产生了3条主要的滑裂面,其中深部不均匀沉降区域附近的滑裂面是明显的滑动破坏,基础附近的滑裂面以张拉破坏为主;2)深部不均匀沉降首先导致了土体内部发生由下至上的滑动破坏,进而使桩基础发生了失稳,最终导致基础附近发生由上至下的破坏;3)深部不均匀沉降范围通过影响上部土体的变形局部化的时空分布情况改变了土坡滑裂面的位置与形状;4)深部不均匀沉降条件对土坡的影响存在一定的范围,影响区边界均呈绕桩分布。

The geological conditions and geotechnical engineering problems are complex and changeable in China.As the construction of engineering projects,deep non-uniform settlement conditions(such as underground coal mining,foundation pit excavation and groundwater level change)can lead to serious deformation and failure of the slopes and foundations overlying them.Pile foundation is a common method of slope reinforcement in engineering projects.Therefore,it is necessary to figure out the failure behaviors of pile foundations under deep non-uniform settlement conditions.Centrifuge model tests were conducted to investigate the deformation and failure behavior of pile foundations under the condition of deep non-uniform settlement which was simulated by the hydraulic system in different ranges.The influence mechanism of deep non-uniform settlement and the failure mechanism of pile foundation were investigated.The observation results are as follows:1)under the condition of deep non-uniform settlement,there were three main slip surfaces in the slopes,among which the slip surfaces near the deep non-uniform settlement area were obvious sliding failure and the sliding surface near the foundation was mainly tensile failure;2)the deep non-uniform settlement first led to the slip failure inside the soil from bottom to top,and then led to the instability of the pile foundations,and finally led to the slip surface near the foundation from top to bottom;3)the range of deep non-uniform settlement changed the location and shape of the slip surfaces of the slopes by influencing the spatial and temporal distribution of the deformation localization;4)there was an influence range of deep non-uniform settlement condition,and the boundary of the influence range was distributed around piles.