基于尖点突变模型的地震液化和孔压研究
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摘要
地震液化是一种严重的自然灾害 ,然而如何准确判断液化目前作的还很不成功。本文以经过持时修正的能量函数和经过粘粒及上覆压力修正的标贯击数为控制变量 ,以孔压发展为状态变量 ,根据液化的物理意义、室内孔压发展曲线的特点和国内外实测液化资料 ,建立了基于修正Zeeman突变方程的孔压液化发展模型。在此基础上 ,利用统计学中控制“弃真”概率的方法 ,确定了分叉曲线和新旧坐标之间的转换关系并且从统计的角度给出了不同土的孔压发展曲线。从孔压发展曲线看 ,对于R >0的任何土 ,超静水压力均达不到 1,其实这正好反映了宏观液化现象。在宏观震害中 ,只要有喷水冒砂现象即认为是液化 ,超静水压力只要能克服埋深而无须达到上覆压力即可使地下水到达地面从而显现宏观液化现象。检验结果表明这一模型是合理的。
Earthquake liquefaction, a serious natural disaster, cannot be predicted successfully enough up to now. A modified model based on Zeeman equation of cusp catastrophe, which illustrates progress of liquefaction, is established, where the earthquake energy function corrected by duration and, the below count of SPT by clay content and overburden pressure, are taken as two individual controlling variables, the ratio of shake-inducing pore water pressure to effective confining pressure is considered as the state variable. Simultaneously, the development pattern of pore water pressure induced by cyclic loading under undrained conditions achieved by experimental tests, triggering condition of liquefaction based on pore water pressure and damage records of liquefaction observed in previous earthquakes are taken into account. The statistical method based on the validation hypothesis for controlling the first type of error is used to determine parameters, bifurcated curve and transformation relationship, the curves of earthquake-induced pore water pressure are given for various kinds of soils. It is found that the ratio is smaller than unit for various soils as R is larger than zero and this conclusion coincides well with the earthquake liquefaction phenomenon. Earthquake liquefaction occurrence can be defined when water jets or sand boils from underground which induced by water pressure only when it is larger than depth of water table and unnecessaryly larger than effective confining pressure. It is verified by the test results that the proposed model is reasonable and expected to predict liquefaction potential and shake-inducing pore water pressure.
Earthquake liquefaction, a serious natural disaster, cannot be predicted successfully enough up to now. A modified model based on Zeeman equation of cusp catastrophe, which illustrates progress of liquefaction, is established, where the earthquake energy function corrected by duration and, the below count of SPT by clay content and overburden pressure, are taken as two individual controlling variables, the ratio of shake-inducing pore water pressure to effective confining pressure is considered as the state variable. Simultaneously, the development pattern of pore water pressure induced by cyclic loading under undrained conditions achieved by experimental tests, triggering condition of liquefaction based on pore water pressure and damage records of liquefaction observed in previous earthquakes are taken into account. The statistical method based on the validation hypothesis for controlling the first type of error is used to determine parameters, bifurcated curve and transformation relationship, the curves of earthquake-induced pore water pressure are given for various kinds of soils. It is found that the ratio is smaller than unit for various soils as R is larger than zero and this conclusion coincides well with the earthquake liquefaction phenomenon. Earthquake liquefaction occurrence can be defined when water jets or sand boils from underground which induced by water pressure only when it is larger than depth of water table and unnecessaryly larger than effective confining pressure. It is verified by the test results that the proposed model is reasonable and expected to predict liquefaction potential and shake-inducing pore water pressure.
引文
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6 何广讷,张业民,土本构关系的尖点突变模式[J].固体力学学报,1991,12(3):109～206
7 刘军,缓倾角层状岩体失稳的尖点突变模型研究[J].岩土工程学报,2001,23(1):42～44
8 张业民,宋长清等,软粘土流动性的尖顶突变模型分析[J].岩土工程学报,1995,17(4):67～70
9 李顺群等,压力超过分叉荷载时中点屈曲位移的确定[J].哈尔滨工业大学学报,2003,35(4):495～501
10何广讷,土工的若干新理论研究与应用[M ].北京:水利电力出版社,1994
11李顺群,张吉明等,考虑持时作用的地震能量表达式[J].辽宁工程技术大学学报,2004,23(3):306～308
12钟龙辉,轻亚粘土地震液化判别方法的分析[J].岩土工程学报,1980,2(3):113～122
13李顺群,土液化的突变模型研究[D].锦州:辽宁工学院,2002
2 SeedHB ,DynamicanalysisoftheslideinthelowerSanFernandodamduringtheearthquakeofFeb.91971[J].JournaloftheGeotechnicalEngineeringDivision,ASCE ,1976,101(GT9):66～78
3 SeedHB ,Evaluationofsoilliquefactioneffectsonlevelgrounddur ingearthquake[A ].LiquefactionProblemsinGeotechnicalEngi neering[C].ASCENationalConvention,1976,1～104
4 SeedHBandLeeKL ,Liquefactionofsaturatedsandsduringcyclicloading[J].JournalofSoilMechanicsandFoundationEngineeringDivision,ASCE ,1966,(SM 6):105～134
5 凌复华译,突变理论及其应用[M ].上海:上海交通大学出版社,1987
6 何广讷,张业民,土本构关系的尖点突变模式[J].固体力学学报,1991,12(3):109～206
7 刘军,缓倾角层状岩体失稳的尖点突变模型研究[J].岩土工程学报,2001,23(1):42～44
8 张业民,宋长清等,软粘土流动性的尖顶突变模型分析[J].岩土工程学报,1995,17(4):67～70
9 李顺群等,压力超过分叉荷载时中点屈曲位移的确定[J].哈尔滨工业大学学报,2003,35(4):495～501
10何广讷,土工的若干新理论研究与应用[M ].北京:水利电力出版社,1994
11李顺群,张吉明等,考虑持时作用的地震能量表达式[J].辽宁工程技术大学学报,2004,23(3):306～308
12钟龙辉,轻亚粘土地震液化判别方法的分析[J].岩土工程学报,1980,2(3):113～122
13李顺群,土液化的突变模型研究[D].锦州:辽宁工学院,2002
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