软弱土层的厚度及埋深对深厚软弱场地地震效应的影响
|
摘要
就软弱土层的埋深和厚度对深厚场地地震动的影响进行了数值分析。场地1、场地2和场地3分别选自南京、盐城和天津。场地1、场地2用于分析软弱表层土的厚度对地表地震动参数的影响:场地1的软弱表层土厚度从2m依次增加到30m,构造了18个土层剖面;场地2的软弱表层土的厚度从2m依次增加到36m,构造了21个土层剖面。场地3用于分析软弱夹层的埋深和厚度对地表地震动参数的影响:软弱夹层的埋深从2m增加到62m,构造了16个剖面;软弱夹层的厚度从2m增加到10m,构造了5个剖面。选用Taft、ElCentro和Northridge地震记录作为输入地震动,将Taft、ElCentro和Northridge地震波加速度时程的峰值水平调整为0.35m/s2,0.70m/s2和0.98m/s2,利用程序SHAKE91对不同的构造剖面、不同的输入地震波及不同的峰值加速度水平,共进行了507种组合的场地地震反应分析。分析表明:对于给定的输入地震动条件,当软弱表层土的厚度超过一定界限值时,地表加速度峰值及放大系数的变化已不很明显;当软弱表层土的厚度超过一定界限值时,加速度放大系数会小于1,也即软弱表层土可起到减震的作用;对于同一场地,输入地震动强度越大,此软表层厚度值越小。对于给定的输入地震动和峰值加速度水平,随着软弱夹层埋深的增加,地表加速度峰值和放大系数λ都有减小的趋
The paper analyses the effect of depth and thickness of soft soil layer on earthquake ground motions of deep soft site. Site 1、Site 2 and Site 3 are from Nanjing、Yancheng and Tianjin cities,respectively. The effect of the thickness of soft superficial soils for Site 1 and Site 2 is analyzed: the thickness of soft superficial soils for Site 1 is increased from 2m to 30m, and 18 site profiles are constituted; the thickness of soft superficial soils for Site 2 is increased from 2m to 36m, and 21 site profiles are constituted. The effect of the depth and the thickness of soft interlayer for Site 3 is analyzed: the depth of soft interlayer is increased from 2m to 62m, and 16 site profiles are constituted; the thickness of soft interlayer is increased from 2m to 10m, and 5 site profiles are constituted. In numerical analysis earthquake acceleration time-histories of Taft record、El Centro record and Northridge record are regarded as input ground motion, and their peak values of acceleration time-histories are adjusted as 0.35m/s~(2)、0.70 m/s~(2)and 0.98 m/s~(2)in turn. The numerical analyses of 507 cases are accomplished by program SHAKE91, the following conclusions can be obtained: when the depth of soft superficial soils exceeds a critical value, the variations of the peak values of ground motion acceleration response and their amplification factors are not obvious, and the latter will be less than 1, namely soft superficial soils can weaken the earthquake response of deep soft sites; the bigger the input ground motion intensity is, the less the critical value of soft superficial soils is; when the depth of soft interlayer is increased, the peak values of ground motion acceleration response and their amplification factors will be lessened; when the depth of soft interlayer exceeds a critical value, the amplification factors will be less than 1; the effect of thickness of soft interlayer on the earthquake response of deep soft sites is related to its depth.
The paper analyses the effect of depth and thickness of soft soil layer on earthquake ground motions of deep soft site. Site 1、Site 2 and Site 3 are from Nanjing、Yancheng and Tianjin cities,respectively. The effect of the thickness of soft superficial soils for Site 1 and Site 2 is analyzed: the thickness of soft superficial soils for Site 1 is increased from 2m to 30m, and 18 site profiles are constituted; the thickness of soft superficial soils for Site 2 is increased from 2m to 36m, and 21 site profiles are constituted. The effect of the depth and the thickness of soft interlayer for Site 3 is analyzed: the depth of soft interlayer is increased from 2m to 62m, and 16 site profiles are constituted; the thickness of soft interlayer is increased from 2m to 10m, and 5 site profiles are constituted. In numerical analysis earthquake acceleration time-histories of Taft record、El Centro record and Northridge record are regarded as input ground motion, and their peak values of acceleration time-histories are adjusted as 0.35m/s~(2)、0.70 m/s~(2)and 0.98 m/s~(2)in turn. The numerical analyses of 507 cases are accomplished by program SHAKE91, the following conclusions can be obtained: when the depth of soft superficial soils exceeds a critical value, the variations of the peak values of ground motion acceleration response and their amplification factors are not obvious, and the latter will be less than 1, namely soft superficial soils can weaken the earthquake response of deep soft sites; the bigger the input ground motion intensity is, the less the critical value of soft superficial soils is; when the depth of soft interlayer is increased, the peak values of ground motion acceleration response and their amplification factors will be lessened; when the depth of soft interlayer exceeds a critical value, the amplification factors will be less than 1; the effect of thickness of soft interlayer on the earthquake response of deep soft sites is related to its depth.
引文
[1] 钱胜国.软土夹层地基场地土层地震反应特性研究[J].工程抗震,1994,(1):32-36.
[2] 刘曾武.考虑软弱夹层的影响对设计反应谱修正的简易方法[A].哈尔滨:第四届全国地震工程会议论文集(一)[C].1994:86-91.
[3] 黄玉龙,郭迅,袁一凡,等.软泥夹层对香港软土场地地震反应的影响.自然灾害学报,2000,9(1):109-116.
[4] 李秀领.土层结构对地表加速度峰值的影响.地震工程与工程振动,2003,23(3):35-40.
[5] 陈国兴,朱定华,何启智.GZZ—1型自振柱试验机研制与性能试验.地震工程与工程振动,2003,23(1):110-114.
[6] 王钟琦,谢君斐,石兆吉.地震工程地质导论.地震出版社,1983.
[2] 刘曾武.考虑软弱夹层的影响对设计反应谱修正的简易方法[A].哈尔滨:第四届全国地震工程会议论文集(一)[C].1994:86-91.
[3] 黄玉龙,郭迅,袁一凡,等.软泥夹层对香港软土场地地震反应的影响.自然灾害学报,2000,9(1):109-116.
[4] 李秀领.土层结构对地表加速度峰值的影响.地震工程与工程振动,2003,23(3):35-40.
[5] 陈国兴,朱定华,何启智.GZZ—1型自振柱试验机研制与性能试验.地震工程与工程振动,2003,23(1):110-114.
[6] 王钟琦,谢君斐,石兆吉.地震工程地质导论.地震出版社,1983.
版权所有：© 2023 中国地质图书馆 中国地质调查局地学文献中心