水位波动作用下软土的变形强度特性研究

在我国沿海地区, 过量抽取利用地下水引发了明显的地面沉降, 限制开采量、人工回灌地下水对减轻地面沉降 具有显著效果。开采与回灌地下水促成了地下水位的大幅波动, 使得沿海地区广泛分布的软土层发生了明显的沉 降与回弹变形。为了研究软土在水位波动作用下的变形和强度特性, 利用沉降柱试验装置模拟地下水位波动, 对不 同水位波动次数作用后的软土试样进行了高压固结试验、直剪试验和三轴试验, 研究了水位波动次数对软土变形性 状的影响, 给出了用初始强度指标和含水量表示的、不同水位波动次数作用后的软土残余强度表达式。试验结果表 明: 随着水位波动次数的增加, 软土的变形特性增强而强度特性降低, 黏聚力和内摩擦角随波动次数的增加呈近似 线性降低; 相同水位波动次数下软土试样的强度指标随含水量的增加呈明显下降趋势。研究成果对于探索城市地 下水位波动对地面沉降和承载力变化的作用机理, 提高科学决策水平及减轻环境地质灾害有着重要实际意义和应 用价值。 The excessive ex traction of gr oundw ater caused obv ious g ro und subsidence in the southeastern co astal areas o f China. Ex plo itatio n restrict ion and artificial r echar ge o f gr oundw ater have significant effects on mitig at ing t he g ro und subsidence. These measures lead to dr ast ic f luct uations o f w ater level and sig nificant sett lement and r ebo und deformation of the widespread so ft soil in the coastal areas. In or der to investig ate t he defo rmation and str eng th o f so ft so il under w ater lev el fluctuat ion, by u2 sing the cy linder mo del ex periment dev ice to simulate w ater lev el fluctuatio n, we conducted hig h2pr essure consolidat ion test, di2 r ect shear test, and triax ial t est on the soft soil aft er differ ent times of wat er level fluctuatio n. Based o n the analy sis o f the influ2 ence deg ree of w ater level fluctuation on the deformation behav io r and str eng th characteristics of soft so il, we presented a rela2 tional ex pression of t he residual str eng th o f soft soil aft er differ ent times of w ater lev el fluctuat ion using initial st rength and w a2 ter content. The test results showed that as the fr equency of w ater level fluctuatio n increased, the deformatio n pro perties of the so ft soil wer e enhanced and the str eng th w as reduced. T he cohesion and internal friction ang le decreased linearly w ith the in2 cr ease of water level fluctuations. T he strength index o f the so ft so il under the same times of water lev el fluctuat ion declined significantly w ith the incr ease of wat er co ntent. The r esults have import ant practical sig nificance and application value on ex ploring the action mechanism of w at er level fluctuation o n gr ound subsidence and bearing capacity chang es, impro ving the level o f scien2 tific decision2making , and m itig ating enviro nmental g eolog ical disasters in coastal cities. 国家自然科学基金项目( 40902092)