深海硅藻土微观结构及一维压缩特性研究

Microstructure and one-dimensional compression characteristics of deep-sea diatomite

目前陆上及浅海海相软土的微观结构和压缩特性研究较为广泛,而深海软土的微观结构和压缩特性研究较少,但随着海洋工程向深水发展,深海软土的特性值得关注。硅藻土广泛分布于深海海底,是深海软土的一种,其具有多样性,不遵循软土经典规律的特点,目前国内外对原位未扰动样品研究很少。针对西太平洋(水深为4423~4674 m)原位硅藻土样,通过电镜扫描(scanning electron microscope,简称SEM)、压汞试验(mercury intrusion porosimety,简称MIP)、常规一维压缩固结试验及多级荷载下(单级加载维持7 d)一维压缩固结试验,开展深海硅藻土微观结构、压缩特性及次固结特性的试验研究。试验结果表明:深海硅藻土的压缩指数分布在1.70~1.95之间,较其他陆上及浅海海相软土大0.6~1.2左右;且在固结完成后的蠕变阶段,硅藻土仍长时间发生体积变形,且并未出现变形收敛趋于稳定的态势,可能是由于硅藻颗粒外壳的持续破碎所导致,这一假设已被加载阶段的SEM和MIP试验观测结果所证实。

At present,the microstructure and compression characteristics of marine soft soils in onshore and shallow seas are widely studied,while those of deep-sea soft soils are less studied.However,with the development of marine engineering to deep water,the characteristics of deep-sea soft soils deserve attention.Diatomite is widely distributed in the deep sea and it is a kind of deep sea soft soil.It has diversity and does not follow the characteristics of classical soft soil laws.Currently,there are few studies on in-situ undisturbed samples.To investigate the microstructures,compression characteristics and secondary consolidation properties of deep-sea diatomite,scanning electron microscope(SEM)analysis,mercury intrusion porosimetry(MIP)tests,traditional oedometer tests and multistage oedometer tests(7-day loading for each stage)were carried out on diatomite sampled from the western Pacific Ocean at the depth between 4423 and 4674 meters.The experimental results show that the compression index of deep-sea diatomite ranges from 1.7 to 1.95,which is about 0.6 to 1.2 larger than that of other terrestrial and shallow marine soft soils.In addition,in the creep stage after consolidation,diatomite still has volume deformation for a long time,and there is no stable trend of deformation convergence,which may be caused by the continuous breaking of the shell of diatom particles.This hypothesis has been confirmed by SEM and MIP tests observation results in the loading stage.