考虑前期固结影响的吹填软土安全运营阶段微结构演化特征

MICROSCOPIC STRUCTURE EVOLUTION PARAMETERS OF SOFT DREDGER FILL IN STAGE OF SAFE OPERATION HYPERPLASIA WITH PRECONSOLIDATION EFFECT

天津滨海新区吹填土为高黏粒含量细粒土,具有孔隙比大、压缩性高、强度低等特点。虽然成土时间短,但具有一定的结构性。土体微观结构决定土体的力学性质,在工程实际中,经过固结处理后的吹填土在安全运营阶段由于上部荷载的持续作用,结构性也会发生变化。为了研究此过程中微结构演化特征,本文试验土样为天津滨海新区重塑土,将其进行先期固结与后期不排水蠕变试验,模拟固结排水地基处理后吹填土安全运营过程,并在此过程中取样进行微结构制样及电镜扫描,定量化分析微观参数的演化规律。试验结果表明:经过固结排水后的吹填软土在持续荷载作用下,土中颗粒和孔隙数量都呈减少趋势,颗粒等效直径、形态比都增大,孔隙等效直径、形态比则呈相反趋势,且在蠕变初期这些变化较为明显,后期变化逐渐趋于平稳。前期固结时间越长,蠕变开始时结构性参数体现出土体结构性越强,固结过程中偏压和固结时间对土体结构性的影响一致。

The soft dredger fill has the characteristic of large void ratio,strong compressibility and low strength. It is fine grain soil of high clay content. Although the short soil formation time,it has certain structure strength.Mechanical property of soil depends on soil＇s microstructure. In engineering practice,the structural strength of soil increases in the stage of safe operation because of the sustained pressure on the soft dredger fill that has ground treatment. To study the microscopic parameter evolution of soft dredger fill in the process of hyperplasia,the remoulded soil from Binhai New Area of Tianjin is used to be the test material of complete structural deterioration.The variation of grain and pore count,equivalent diameter and aspect ratio is analyzed quantitatively in the processof hyperplasia of structure strength with Scanning Electron Microscope. The result of tests shows that： in the process of hyperplasia of structure strength,the count of grain and pore and equivalent diameter decline,while aspect ratio of grain and pore,and equivalent diameter increase. The change is obvious at the beginning of the generation of structure strength. The longer consolidation time,the stronger constitutive property is. Deviator pressure and consolidation time have the same effect on the constitutive property of soil.