各向异性固结下饱和珊瑚砂超静孔压增长的能量模式

AN ENERGY-BASED MODEL FOR GENERATION OF EXCESS PORE WATER PRESSURE IN SATURATED CORAL SAND UNDER ANISOTROPIC CONSOLIDATION

针对具有不同初始物理状态的饱和珊瑚砂,开展了不同固结条件下循环应力主轴90°跳转的系列不排水循环剪切试验,研究了细粒含量FC、初始相对密度D_(r)、固结条件(固结围压p′0、固结方向角α_(c)和固结比k_(c))以及循环加载条件(循环加载频率、循环加载路径和循环应力比)对饱和珊瑚砂的超静孔压u_(e)与累积耗散能W关系的影响。u_(e)与W的关系受土性条件和固结条件的影响显著,而不依赖于循环加载条件。当FC低于阈值细粒含量时,试样液化所需累积耗散能(W_(s))随FC的增加而减少,而随D_(r)的增大而增大。均等固结条件下试样液化所需累积耗散能随p′0的增加而增加;对于各向异性固结试样,u_(e)的稳定值随αc的增加呈现出先增后减的趋势;而随kc的增大而减小。引入等效骨架孔隙比e_(sk)^(*)描述珊瑚砂的物理状态,发现均等固结条件下饱和珊瑚砂的超静孔压比r_(u)与规准化累积耗散能WR的关系曲线具有唯一性,提出考虑α_(c)及k_(c)的经验参数,建立了适用于不同物理状态和复杂应力条件的饱和珊瑚砂修正ru随WR增长的反正切函数能量模型。

A series of undrained cyclic shear tests were carried out on saturated coral sands with different initial physical states,as they were subjected to rotations of 90°in the paths of cyclic stress under various consolidation conditions.An important finding from the test results is that both soil properties(fines content FC and initial relative density D_(r))and consolidation conditions(consolidation confining pressure p_(0)'the consolidation inclinationαc and the consolidation ratio k_(c))significantly affect the relationship between u_(e)and W,and are less affected by cyclic loading conditions(cyclic loading frequency,cyclic stress path and cyclic stress ratio).When FC is less than the threshold fines content,the cumulative dissipated energy required for lique faction(W_(s))increases with the increase of FC and decreases with the increase of D_(r).Under isotropic consolidation conditions,W_(s)increases significantly with the increase of.For the anisotropically consolidated specimens,the stable value of u_(e)first increases and then decreases with the increase ofα_(c),and decreases with the increase of k_(c).The equivalent intergranular void ratio(e_(sk)^(*))was introduced to reflect the effects of FC,physical states of the particles and inter-particle contact on physical properties of coral sand.The relationship between the excess pore water pressure ratio(r_(u))and the normalized cumulative dissipation energy(W_(R))of saturated coral sand under isotropic consolidation conditions is unique.The empirical parameters consideringαc and kc are put forward,and the arctangent function model of modified r_(u) increasing with W_(R) is established for saturated coral sand with different physical states and complex stress conditions.