黄河口不同强度粉土液化特性的试验研究

Liquefaction characteristics of silts with different strengths at Yellow River estuary

研制真空压缩装置以制备不同强度的粉土土样,并进行动三轴试验,测试不同强度粉土的液化特性。建立了土的强度与动剪应力比的关系,确立孔压增长模型及其参数,探讨土的强度和动应力对液化的影响。结果表明,(1)真空压缩装置制备土样过程中,土体超孔压在24 h内基本消散完毕,28 d贯入阻力达300～400 N,不排水抗剪强度达8 kPa,达到黄河口软弱土的强度;(2)土的强度与动剪应力比基本呈线性关系,且土的强度越高,孔压增长曲线越呈现上凸趋势,破坏时的孔压比也越大;(3)指数模型能够较好模拟黄河口粉土孔压增长情况,其中参数a和b分别位于0.77～5.63和0.17～4.65之间;对于孔压比上限,参数a,b分别为0.92和4.65;孔压比下限,参数a,b分别为1.25和0.89。

A vacuum compression device is developed for preparing silt soil samples with different strengths,and triaxial test is performed for measuring liquefaction characteristics of those soil samples.The relationship between soil strength and cyclic shear stress ratio,pore pressure growth model and its parameters are established;and the impact of the soil strength and the dynamic stress on the liquefaction is discussed.Some conclusions are drawn as follows.（1） During soil samples preparation in the vacuum compression device,excess pore pressure dissipated completely within 24 hours,penetration resistance up to 300-400 N;undrained shear strength up to 8 kPa,reached weak soil strength at the Yellow River estuary.（2） The relationship between soil strength and cyclic shear stress ratio is basically linear;and the higher soil strength,curve of pore pressure on the growth showing the more convex trend,the greater pore pressure ratio reached when destroyed.（3） Index model can better simulate pore-water pressure growth of silt at the Yellow River estuary,where the parameters a and b are located between 0.77-5.63 and 0.17-4.65,respectively;for the pore pressure ratio upper limit,the parameters a and b are 0.92 and 4.65 respectively;for pore pressure lower limit,the parameters a and b are 1.25 and 0.89 respectively.