黄河口粉土液化过程的现场振动试验研究
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摘要
采用不同重量的重锤自不同高度处自由落体捶击荷载板,研究不同能量大小的循环荷载对黄河水下三角洲土体的动力响应过程。在土体内埋设检波器探头和孔压探头,用以监测荷载能量在土体内的吸收传播和引起的孔压变化,同时在每轮振动前后分别测量土体的强度变化。通过研究发现,80%的振动能量在0.6m土体深度内吸收,能量的衰减量沿深度可用对数曲线表示;振动能量越大,土体产生的超孔压越大,且超孔压所在的深度也越大;根据孔压随振次的变化关系,将现场振动过程中的孔压变化分为四个阶段,即初始阶段、增长阶段、稳定阶段和衰减阶段。最后,讨论振动荷载引起的土体强度变化以及土体液化与振动能量的关系,提出土体临界液化功率的概念,并给出若干深度的范围值。
The dynamic response of seabed induced by cyclic loading at the subaqueous delta of the Yellow River is simulated by hitting a load plate with hammers of different weights dropped freely at different heights. In the seabed, the vibration detectors and pore pressure gauges are buried to observe the vibration energy dissipation and pore pressure variation, and the soil strength is also measured before and after vibrations. Through the observation, some conclusions are drawn: 80% of the loading energy is absorbed above depth of 0.6 m, and the relationship between dissipation degree and depth can be expressed by the logarithmic curve; the excess pore pressure increases with the increase of the vibration energy; according to the variation of pore pressure with vibration times, the variation of pore pressure can be divided into four stages—initial stage, growing stage, stabilizing stage and attenuating stage. Finally, the variation of soil strength induced by vibration and the relationship between soil liquefaction and vibration energy are discussed, and the concept of critical liquefaction power is put forward.
The dynamic response of seabed induced by cyclic loading at the subaqueous delta of the Yellow River is simulated by hitting a load plate with hammers of different weights dropped freely at different heights. In the seabed, the vibration detectors and pore pressure gauges are buried to observe the vibration energy dissipation and pore pressure variation, and the soil strength is also measured before and after vibrations. Through the observation, some conclusions are drawn: 80% of the loading energy is absorbed above depth of 0.6 m, and the relationship between dissipation degree and depth can be expressed by the logarithmic curve; the excess pore pressure increases with the increase of the vibration energy; according to the variation of pore pressure with vibration times, the variation of pore pressure can be divided into four stages—initial stage, growing stage, stabilizing stage and attenuating stage. Finally, the variation of soil strength induced by vibration and the relationship between soil liquefaction and vibration energy are discussed, and the concept of critical liquefaction power is put forward.
引文
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[13]马德翠,单红仙,周其健.黄河口饱和粉质土振动响应的原位试验研究[J].地震工程与工程振动,2005,25(10):1-5.(MA De-cui,SHAN Hong-xian,ZHOU Qi-jian.In-situ test study on dynamics response of saturated silt soils under cyclic loading in estuary of Yellow River[J].Earthquake Engineering and Engineering Vibration,2005,25(10):1-5.(in Chinese))
[14]WIT P D,KRANENBURG C.The wave-induced liquefaction of cohesive sediment beds[J].Estuarine,Coastal and Shelf Estuarine,1997,45(2):261-271.
[15]TZANG S Y,OU S H.Laboratory flume study on monochromatic wave-fine sandy bed interactions(part1)[J].Soil Fluidization Coastal Engineering,2006,53:965-982.
[2]CHRISTIAN J T,TAYLOR P K,YEN J K C,et al.Large diameter underwater pipeline for nuclear plant designed against liquefaction[C]//The10th Offshore Technology Conference,Houston,1974:597-606.
[3]DUNLAP W,BRYANT W R,WILLIAMS G N,et al.Storm wave effects on deltaic sediments-results of EASWAB I and II[C]//Port and Ocean Engineering Under Arctic Conditions(POAC79),Norwegian Institute of Technology,1979:899-920
[4]MIYAMOTO T,YOSHINAGA S,SOGA F,et al.Seismic prospecting method applied to the detection of offshore breakwater units setting in the seabed[J].Coastal Engineering in Japan,1989,32:103-112.
[5]李广雪,庄克琳,姜玉池.黄河三角洲沉积体的工程不稳定性[J].海洋地质与第四纪地质,2000,20(6):21-26.(LI Guang-xue,ZHUANG Ke-lin,JIANG Yu-chi.Engineering instability of the deposition bodies in the Yellow River delta[J].Marine Geology and Quaternary Geology,2000,20(6):21-26.(in Chinese))
[6]常瑞芳,陈樟榕,陈为民,等.老黄河口水下三角洲前缘底坡不稳定地形近期演化与控制[J].青岛海洋大学学报,2000,30(1):159-164.(CHANG Rui-fang,CHEN Zhang-rong,CHEN Wei-min,et al.The recent evolution and controlling factors of unstable seabed topography of the old Yellow River sub-aqueous delta[J].Journal of Ocean University,2000,30(1):159-164.(in Chinese))
[7]杨少丽,沈渭铨,杨作升,等.波浪作用下海底粉砂液化的机理分析[J].岩土工程学报,1995,17(4):28-37.(YANG Shao-li,SHEN Wei-shuan,YANG Zuo-sheng,et al.The mechanism analysis of seafloor silt liquefaction under wave loads[J].Chinese Journal of Geotechnical Engineering,1995,17(4):28-37.(in Chinese))
[8]贾永刚,史文君,单红仙,等.黄河口粉土强度丧失与恢复过程现场振动试验研究[J].岩土力学,2006,26(3):351-358.(JIA Yong-gang,SHI Wen-jun,SHAN Hong-xian,et al.In-situ test study on silt strength’s loss and recovery due to vibration load in the Yellow River mouth[J].Rock and Soil Mechanics,2006,26(3):351-358.(in Chinese))
[9]单红仙,段兆臣,刘正银,等.粉质土重复振动液化与效果研究[J].水利学报,2006(1):75-81.(SHAN Hong-xian,DUAN Zhao-chen,LIU Zheng-yin,et al.Repeated liquefaction and the effect on properties of silt[J].Journal of Hydraulic Engineering,2006(1):75-81.(in Chinese))
[10]许国辉,单红仙,贾永刚.黄河水下三角洲沉积物在循环荷载作用下土体中孔压变化实验研究[J].中国海洋大学学报,2003,33(1):80-86.(XU Guo-hui,SHAN Hong-xian,JIA Yong-gang.Experimental research on the variation of pore-pressure under cyclic loading in the sub-aqueous Yellow River delta[J].Journal of China Ocean University,2003,33(1):80-86.(in Chinese))
[11]臧启运.黄河三角洲近岸泥沙[M].北京:海洋出版社,1996:65.(ZANG Qi-yun.Off-shore silt of Yellow River delta[M].Beijing:Ocean Press,1996:65.(in Chinese))
[12]成国栋,薛春汀.黄河三角洲沉积地质学[M].北京:地质出版社,1997:39.(CHENG Guo-dong,XUE Chun-ting.The Yellow River delta deposition geology[M].Beijing:Geological Publishing House,1997:39.(in Chinese))
[13]马德翠,单红仙,周其健.黄河口饱和粉质土振动响应的原位试验研究[J].地震工程与工程振动,2005,25(10):1-5.(MA De-cui,SHAN Hong-xian,ZHOU Qi-jian.In-situ test study on dynamics response of saturated silt soils under cyclic loading in estuary of Yellow River[J].Earthquake Engineering and Engineering Vibration,2005,25(10):1-5.(in Chinese))
[14]WIT P D,KRANENBURG C.The wave-induced liquefaction of cohesive sediment beds[J].Estuarine,Coastal and Shelf Estuarine,1997,45(2):261-271.
[15]TZANG S Y,OU S H.Laboratory flume study on monochromatic wave-fine sandy bed interactions(part1)[J].Soil Fluidization Coastal Engineering,2006,53:965-982.
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