考虑深海能源土结构性影响的弹塑性本构模型

Elastic-plastic Constitutive Model Considering Structural Effects of Deep-sea Energy Soil

深海能源土是指水合物以不同赋存模式填充于孔隙中的海底沉积物。水合物的填充效应会对能源土的密度和孔隙比产生较大影响。水合物的胶结效应会产生随饱和度增大而增大的胶结力,两种效应共同影响着深海能源土的复杂力学特性。同时能源土也是一种特殊的结构性土,其骨架颗粒、孔隙性状和排列方式均会对能源土的强度、应变软化和剪胀剪缩等特性有影响。在CSUH模型的框架下,通过建立与水合物饱和度相关的压硬性参数来反映水合物对能源土压缩特性的影响。其次考虑水合物填充效应的影响,推导出了能源土的实际初始孔隙比计算式,并将其引入至能源土的状态参数中来反映其剪胀特性。最后将用于描述土体损伤效应的结构性参数与水合物饱和度相关的胶结性参数作为硬化规律,建立了一个考虑水合物填充效应的结构性深海能源土的弹塑性本构模型。通过与室内试验结果比较,验证了该模型可有效反映能源土在不同水合物饱和度和围压条件下的应变硬化及软化、体积剪胀剪缩等复杂力学特性。

Deep-sea energy soil refers to deep-sea sediments where gas hydrates are filled in various modes within the pores.The filling effect of gas hydrates significantly impacts the density and porosity ratio of deep-sea energy soil.Additionally,the cementation effect of gas hydrates generates increasing bonding force with increasing saturation,jointly affecting the complex mechanical properties of deep-sea energy soil.Furthermore,deep-sea energy soil is a distinctive structural soil,wherein the particle framework,pore characteristics,and arrangement influence its strength,strain softening,and characteristics such as shear dilation and contraction.Within the framework of the CSUH model,this research reflected the compressibility characteristics of gas hydrates on energy soil by establishing pressure-hardening parameters related to gas hydrate saturation.Furthermore,considering the influence of gas hydrate filling effects,the actual initial porosity calculation formula for energy soil was derived and incorporated into the state parameters to reflect its shear dilation characteristics.Finally,utilizing structural parameters describing soil damage effects and cementation parameters related to gas hydrate saturation as hardening rules,an elastoplastic constitutive model for structural deep-sea energy soil considering gas hydrate filling effects was established.Comparative analysis with indoor experimental results validates the model's efficacy in effectively reflecting the complex mechanical properties of energy soil under various gas hydrate saturations and confining pressure conditions,including strain hardening and softening,as well as volume shear dilation and contraction.