浸水对湿陷性黄土中桩基承载特性影响的模型试验

湿陷性黄土桩基现场浸水试验一般情况下是先浸水然后等到黄土的湿陷性彻底发挥以后再加载使桩土体系沉降,最后趋于稳定的状态,在桩基正常使用过程中由于雨雪等原因桩基也会遇到先加载后浸水的情况。为了探究两种浸水工况对桩基承载特性的影响,设计了室内桩土模型试验。结果表明:与桩土体系先加载后浸水相比,先浸水后加载时桩基中性点位置提高,中性点位置随着浸水量的增大沿桩身向下移动,桩侧负摩阻力极大值增大46%,负摩阻力极值点沿桩身下降170 mm,桩基正摩阻力极大值提高46%,正摩阻力极值点沿桩身上升70 mm;两种浸水工况下的桩身轴力沿埋深的变化趋势都是先增大后减小的抛物线形;桩周土体在未浸水和先浸水后加载两种工况下的桩基极限承载力一样大。

Model Test of Water Immersion Influence on Bearing Properties of Pile Foundation in Collapsible Loess

The in-situ soaking test of collapsible loess pile foundation conducts soaking first and then loads the pile soil to get it settling after the loess collapses completely,finally the pile soil tends to get stable. In the process of pile foundation normal service,the pile encounters loading first and then soaking due to rain and snow. According to the two kinds of flooding sequence,indoor model pile soil test is planned. The test results show that compared with first loading,the first-soaking-then-loading improves the pile foundation neutral point,the position of the neutral point moves down the pile as the amount of soaked water increases; the pile side negative friction resistance increases by a maximum of 46%,the negative friction resistance extreme point drops by 170 mm along the pile,the pile foundation positive friction resistance increases by 46% and the positive friction resistance extreme points rises by 70 mm along the pile; under the two conditions of soaking,the variation tendency of the axial force along the burial depth is in the form of a parabolic which first increases and then decreases; the ultimate bearing capacity of the pile foundation is equal when the pile-soil system is loaded under two conditions without submergence and with first-submergence.