黄土高原河谷城市潜在地震液化特征及灾害预测
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摘要
以天水市区为例,在研究区内采集砂土和原状黄土试样,通过对所取试样的室内动三轴液化试验结果进行分析,探讨黄土高原河谷城市的土壤地震液化特征。采用Seed-Idriss简化判别法,对研究区内土壤在不同等效烈度地震作用下的液化势进行判别,并结合黄土高原河谷城市的地形地貌和地质构造特征,对黄土高原河谷城市土壤地震液化灾害进行预测。结果表明:黄土高原河谷城市的饱和土体在地震作用下,由于黄土质地疏松,抗液化强度更低,在Ⅶ度的地震作用下即可液化;液化不会产生喷水现象,但易导致滑坡和泥流灾害,其抗液化强度主要受密度和塑性指数的影响。砂土在Ⅷ度及以上地震作用下液化,且存在喷水冒砂现象,可导致地面开裂、地基不均匀沉降和建筑地基失稳破坏;粒径为影响砂土液化的最主要因素,粉砂比细砂更易液化。
Taking Tianshui urban areas as an example, the results of dynamic triaxial liquefaction test on sand and undisturbed loess samples taken from the study area are analyzed. And the liquefaction characteristics of the soil in the valley cities located in the Loess Plateau are discussed. Moreover, liquefaction potential of the soil under the different equivalent intensity earthquakes are evaluated by using Seed-Idriss simplified discriminant method. In addition, the soil earthquake liquefaction disasters of the valley cities in the Loess Plateau are predicted in combination of topography and geological features. The results show that: the liquefaction characteristics of the saturated soil in loess plateau valley cities are different under seismic action. The liquefaction strength of it is quite lower because loess is a loose soil. So it can be liquefied when the seismic intensity rise up to Ⅶ degree. The liquefaction will not produce surface loess boiling, but it often leads to landslides and mudflow disaster. The liquefaction strength is mainly affected by the density and the plastic index of the loess. However, the sand will be liquefied when the seismic intensity is up to Ⅷ degree. The liquefaction will produce surface sand boiling and lead to ground cracks, uneven settlement of foundation and instability or failure of buildings. Particle size is the main factor influencing sand liquefaction. The silt sand is more easily liquefied than the fine sand.
Taking Tianshui urban areas as an example, the results of dynamic triaxial liquefaction test on sand and undisturbed loess samples taken from the study area are analyzed. And the liquefaction characteristics of the soil in the valley cities located in the Loess Plateau are discussed. Moreover, liquefaction potential of the soil under the different equivalent intensity earthquakes are evaluated by using Seed-Idriss simplified discriminant method. In addition, the soil earthquake liquefaction disasters of the valley cities in the Loess Plateau are predicted in combination of topography and geological features. The results show that: the liquefaction characteristics of the saturated soil in loess plateau valley cities are different under seismic action. The liquefaction strength of it is quite lower because loess is a loose soil. So it can be liquefied when the seismic intensity rise up to Ⅶ degree. The liquefaction will not produce surface loess boiling, but it often leads to landslides and mudflow disaster. The liquefaction strength is mainly affected by the density and the plastic index of the loess. However, the sand will be liquefied when the seismic intensity is up to Ⅷ degree. The liquefaction will produce surface sand boiling and lead to ground cracks, uneven settlement of foundation and instability or failure of buildings. Particle size is the main factor influencing sand liquefaction. The silt sand is more easily liquefied than the fine sand.
引文
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[11]白铭学,张苏民.高烈度地震时黄土地层的液化移动[J].工程勘察,1990,2(6):1-5(Bai Mingxue,Zhang Sumin.Loess liquefaction flow in high intensity earthquake[J].Geotechnical Investigation and Surveying,1990,2(6):1-5(in Chinese))
[12]王家鼎.高速黄土滑坡的一种机理——饱和黄土蠕动液化[J].地质评论,1992,38(6):532-539(Wang Jiading.A mechanism of high-speed loess landslides—saturated loess creeping liquefaction[J].Geological Review,1992,38(6):532-539(in Chinese))
[13]王峻,王兰民,王平,等.不同地区饱和黄土液化特性研究[J].水文地质工程地质,2011,38(5):54-56(Wang Jun,Wang Lanmin,Wang Ping,et al.A study on liquefaction characteristics of saturated loess in different regions[J].Hydrogeology&Engineering Geology,2011,38(5):54-56(in Chinese))
[14]王兰民,袁中夏,汪国烈.饱和黄土场地液化的工程初判和详判指标与方法研究[J].地震工程学报,2013,35(1):1-8(Wang Lanmin,Yuan Zhongxia,Wang Guolie.Study on method for preliminary and detailed evaluation on liquefaction of loess sites[J].China Earthquake Engineering Journal,2013,35(1):1-8(in Chinese))
[15]王谦,王兰民,王峻,等.基于密度控制理论的饱和黄土地基抗液化处理指标研究[J].岩土工程学报,2013,35(S2):844-847(Wang Qian,Wang Lanmin,Wang Jun,et al.Indices of anti-liquefaction treatment of saturated compacted loess foundation based on theory of density control[J].Chinese Journal of Geotechnical Engineering,2013,35(S2):844-847(in Chinese))
[2]Seed H B.Design problems in soil liquefaction[J].Journal of Geotechnical Engineering,1987,113(8):827-845
[3]Vaid Y P,Thomas J.Liquefaction and postliquefaction behavior of sand[J].Journal of Geotechnical Engineering,1995,121(2):163-173
[4]Seed H B,Idriss I M,Arango I.Evaluation of liquefaction potential using field performance data[J].Journal of Geotechnical Engineering,1983,109(3):458-482
[5]张建民,时松孝次,田屋裕司.饱和砂土液化后的剪切吸水效应[J].岩土工程学报,1999,21(4):398–404(Zhang Jianmin,Tokimatsu Kohji,Taya Yuhji.Effect of water absorption in shear of post-liquefaction sand[J].Chinese Journal of Geotechnical Engineering,1999,21(4):398–404(in Chinese))
[6]陈育民,刘汉龙,周云东.液化及液化后砂土的流动特性分析[J].岩土工程学报,2006,28(9):1139-1143(Chen Yumin,Liu Hanlong,Zhou Yundong.Analysis on flow characteristics of liquefied and post-liquefied sand[J].Chinese Journal of Geotechnical Engineering,2006,28(9):1139-1143(in Chinese))
[7]刘汉龙.土动力学与土工抗震研究进展综述[J].土木工程学报,2012,45(4):1-17(Liu Hanlong.A review of recent advances in soil dynamics and geotechnical earthquake engineering[J].China Civil Engineering Journal,2012,45(4):1-17(in Chinese))
[8]Boulanger R W,Meyers M W,Mejia L H,et al.Behavior of a fine-grained soil during the Loma Prieta earthquake[J].Canadian Geotechnical Journal,1998,35(1):146-158
[9]Puri V K.Liquefacti on behavior and dynamic properties of loessial(silty)soils[D].Missouri:University of MissouriRolla,1984
[10]Ishihara K,Okusa S,Oyagi N,et al.Liquefaction-induced flow slide in the collapsible loess deposit in soviet Tajik[J].Soils and Foundations,1990,30(4):73-89
[11]白铭学,张苏民.高烈度地震时黄土地层的液化移动[J].工程勘察,1990,2(6):1-5(Bai Mingxue,Zhang Sumin.Loess liquefaction flow in high intensity earthquake[J].Geotechnical Investigation and Surveying,1990,2(6):1-5(in Chinese))
[12]王家鼎.高速黄土滑坡的一种机理——饱和黄土蠕动液化[J].地质评论,1992,38(6):532-539(Wang Jiading.A mechanism of high-speed loess landslides—saturated loess creeping liquefaction[J].Geological Review,1992,38(6):532-539(in Chinese))
[13]王峻,王兰民,王平,等.不同地区饱和黄土液化特性研究[J].水文地质工程地质,2011,38(5):54-56(Wang Jun,Wang Lanmin,Wang Ping,et al.A study on liquefaction characteristics of saturated loess in different regions[J].Hydrogeology&Engineering Geology,2011,38(5):54-56(in Chinese))
[14]王兰民,袁中夏,汪国烈.饱和黄土场地液化的工程初判和详判指标与方法研究[J].地震工程学报,2013,35(1):1-8(Wang Lanmin,Yuan Zhongxia,Wang Guolie.Study on method for preliminary and detailed evaluation on liquefaction of loess sites[J].China Earthquake Engineering Journal,2013,35(1):1-8(in Chinese))
[15]王谦,王兰民,王峻,等.基于密度控制理论的饱和黄土地基抗液化处理指标研究[J].岩土工程学报,2013,35(S2):844-847(Wang Qian,Wang Lanmin,Wang Jun,et al.Indices of anti-liquefaction treatment of saturated compacted loess foundation based on theory of density control[J].Chinese Journal of Geotechnical Engineering,2013,35(S2):844-847(in Chinese))
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