Analytical investigation of disturbance of seabed-sampled soil specimens and its influence on unconfined strength
Analytical investigation of disturbance of seabed-sampled soil specimens and its influence on unconfined strength
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DOI：
10.1016/j.sandf.2018.02.026
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发表时间：
2018-06
影响因子：
3.7
通讯作者：
Sugiyama Yuri;T. Shinya;S. Hide;Iizuka Atsushi
中科院分区：
文献类型：
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作者：
Sugiyama Yuri;T. Shinya;S. Hide;Iizuka Atsushi
鉴于利用海洋空间和开发海底资源的需要，深海海底土的稳定性评价已成为地质力学领域的一项重要挑战。为了研究海床稳定性，必须确定天然地基的强度和刚度。因此，有必要对从海床上取样的土样进行实验室测试，或者通过现场测试来估计强度和刚度。虽然将来进行现场测试来估计海底土壤的硬度和强度可能是合理的，但在进行这些测试之前，仍有必要将现场测试所测得的物理性质与实验室测试所测得的物理性质进行比较。简而言之，土样必须从实际的深海海底取样，并且必须对取样的土样进行实验室力学测试。然而，从海底采样的土壤受到的影响与从地球采样的土壤所受的影响不同。更具体地说，从海底采样的土壤预计会受到干扰的不可忽视的影响。扰动的影响发生在采样过程中，由于溶解气体的蒸发，因为这些土样处于相对较高的压力下，并且含有大量溶解气体的孔隙水。因此，本研究通过数值模拟来研究蒸发溶解气体对取样过程中土样的力学行为和室内试验所确定的不排水抗剪强度的影响。分析表明，取样引起的有效应力降低和超固结、不饱和等因素的共同作用，是由于室内试验确定的土体强度与现场土体强度的差异所致。
In view of the need to utilize ocean space and to develop seabed resources, the assessment of the stability of deep seabed soil has emerged as an important challenge in the field of geomechanics. To study seabed stability, the strength and stiffness of the natural ground must be ascertained. Accordingly, it is necessary either to conduct laboratory testing on soil specimens sampled from the seabed or to estimate the strength and stiffness by in-situ tests. While in the future it may be reasonable to conduct in-situ tests to estimate the stiffness and strength of seabed soil, it will still be necessary to compare the physical properties measured by in-situ testing with those measured by laboratory testing in advance of these determinations. In short, soil specimens must be sampled from the actual deep seabed, and laboratory mechanical tests must be conducted on the sampled soil specimens. However, soil sampled from the ocean bottom is subject to effects that differ from those exerted on soil sampled from the earth. More specifically, the non-negligible effects of disturbance are expected with soil sampled from the ocean bottom. The effects of disturbance occur during the sampling process due to the vaporization of dissolved gases, as these soil specimens are under relatively higher pressure and contain pore water with a high amount of dissolved gases. Therefore, numerical simulations were conducted in the present study to investigate the effects of vaporized dissolved gases on the mechanical behavior of soil specimens during sampling and on the undrained shear strength as determined by laboratory tests. The analyses revealed that the combination of the decreasing effective stress caused by the sampling and factors such as overconsolidation and unsaturation is attributable to the difference between the soil strength ascertained by laboratory testing and the in-situ soil strength.