海洋细粒沉积物中含有相对较大的生物气气泡,初始水深影响气泡存在状态,进而影响含气土强度,导致土体的强度可能增大也可能减小。对嘉兴1号海上风电场现场取土进行重塑,开展一系列不排水三轴剪切试验,旨在比较具有相同固结压力但初始孔隙水压力（与水深有关）不同条件下的含气土的剪切特性。研究发现改变初始孔隙压力,含气土表现出不同的不排水抗剪强度,含气土试样中由剪切引起的超孔隙压力大小取决于初始水深,其可低于具有相同固结压力下的饱和试样（由于在低初始孔隙压力下部分孔隙水进入到相对较大的气泡）,或高于饱和试样（与高初始孔隙压力下相对较小的气泡破裂有关）。因此,在相对较低的初始孔隙压力条件下,气泡的存在有利于增加土体的不排水抗剪强度,反之则会降低土体的不排水抗剪强度。但重塑含气土的临界应力比不受初始孔隙水压力的影响。
Abstract
Marine fine-grained sediments contain relatively large biogas bubbles. Initial water depth affects the existence state of bubbles and thus the strength of gassy soils, which may either increase or decrease the strength of soil. In this study, a series of undrained triaxial tests were carried out to compare the shear characteristics of gassy soils with the same consolidation pressure but different initial pore water pressures （related to water depth）. It is found that the shear strength of the gassy soils varies with initial pore water pressure. The excess pore pressure caused by undrained shearing depends on the initial water depth and can be either lower （due to partial dissipation of pore pressure into relatively large bubbles） or higher （related to collapse of relatively small bubbles at high） than that in the saturated sample with the same consolidation pressure. In a word, the presence of bubbles has beneficially increased undrained shear strength at relatively low pore pressure and vice versa. However, the critical stress ratio for remolding gassy soil is not affected by the initial pore water pressure.
关键词
海上风电 /
土力学 /
抗剪强度 /
临界状态 /
三轴剪切试验
Key words
offshore wind turbines /
soil mechanics /
shear strength /
critical state /
triaxial shear test
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参考文献
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基金
国家重点研发计划“政府间国际科技创新合作/港澳台科技创新合作”重点专项项目（2018YFE0109500）; 国家自然科学基金（52122906; 51779221; 51939010; 51909249）; 浙江省自然科学基金（LHZ20E090001）
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