M5.1地震引起的一个不寻常的砂砾层大范围液化——盐溶的液化活化效应及其机理  

An unusual widespread liquefaction caused bya magnitude 5.1 earthquake———Activation effect of salt dissolution on sand gravel liquefaction and its mechanism

作　　者：钟建华 倪良田[3] 孙宁亮 曹梦春 ZHONG Jianhua;NI Liangtian;SUN Ningliang;CAO Mengchun(State Key Laboratory,China University of Mining and Technology(Beijing),Beijing,100083;School of Geoscience,China University of Petroleum,Qingdao,Shandong,266580;Research Institude of Exploration and Development,Hengli Oilfield Company,SINOPEC,Dongying,Shandong,257000;School of Resources and Material,Northeastern University at Qinhuangdao,Qinghuangdao,Hebei,066004)

机构地区：[1]中国矿业大学(北京)煤炭资源与安全开采国家重点实验室,北京100083 [2]中国石油大学(华东)地球科学与技术学院,山东青岛266580 [3]中国石化胜利油田分公司勘探开发研究院,山东东营257000 [4]东北大学海洋油气勘探国家工程研究中心,河北秦皇岛066004

出　　处：《地质论评》2023年第4期1543-1563,共21页Geological Review

基　　金：国家自然科学基金资助项目“哈密M5.1地震引起的砂砾岩远程液化特点和机理的研究”(编号:41572088)的成果~~。

摘　　要：地震液化阈值是一个非常重要的科学问题,一般认为M5地震不会形成大面积的液化。2009年12月14日,中国新疆哈密市发生了M5.1中等地震,震源深度仅4 km。地震砂脉网格在平面从几十厘米到2 m以上;砂脉纵断面呈楔形、倾斜(平均75.10°),分选较好。通常情况下,它们通过液化和流化分异作用发生在细粒丰富的盐渍砂砾层(SSGL,Salinization Sand—Gravel Layer)和盐粒砂砾层(SGSGL,Salt-Grain—Sand—Gravel Layer)中,尽管没有细粒盖层和源砂,但这些盐渍的砂砾层极易在盐溶后发生活化,颗粒之间的摩擦力骤降,液化上涌而形成砂脉。液化边界距震中可达80 km,甚至可能达到120 km,相当于M7.0~8.0级地震的液化最远距离。哈密地区之所以能在M5.1地震作用下形成远程砂脉,主要由于以下5个优势:(1)砂泥的盐溶液中细粒组分容易发生液化流化。浓盐水能够降低颗粒的剪切能力,平均降低25%~75%左右,使地震液化阈值降低到0.15~0.05 g(以0.2 g为一般阈值)。与此同时,浓盐水由于密度大,盐水可使淡水最小流化速度(Umf)降低12.51%~21.58%,有利于流化。(2)广泛分布的盐渍砂砾层和盐粒砂砾层。(3)震源极浅(深度仅4 km)。(4)基底极浅(深度0~3 m)。(5)表层盐屑混合盖+盐渍砂砾层+盐粒砂砾层+极浅基岩基底组成了特殊的三明治结构。通过对液化流化的形成机理研究表明,砂主要来自砂脉底部的砂砾层的流化分选,流化分选会在砂脉底部的砂砾层中形成一个分选晕。Objectives:The earthquake liquefaction threshold is a very important scientific problem.It is generallybelieved that the earthquake of magnitude 5 will not result in large-scale liquefaction.On December 14,2009,amoderate 5.1 magnitude earthquake struck Hami City in western China’s Xinjiang Province,with a focal depth ofonly 4 kilometers(Figure 1).This paper is to discuss the mechanism of extensive liquefaction caused by Hami 5.1earthquake.Methods:The authors made a detailed field investigation in Hami,Xinjiang,and obtained a lot of valuablegeological information,especially sand dikes and obtained a lot of valuable salt solution activation data through thelaboratory fluidization experiment and salt solution activation experiment,which provided valuable data for furtherstudy of liquefaction activation of saline solution.Results:The liquefaction boundary can be 80 kilometers away from the epicenter,and may even reach 120km,which is equivalent to the epicenter distance of a 7.0~8.0 magnitude earthquake.It is undeniable that theformation of Hami sand dikes,especially the unusually significant liquefaction and fluidization.Seismic sand dikesgrid plane from tens of centimeters to more than 2 meters;The longitudinal section is wedge-shaped and oblique(average 75.10°),and the sorting is good.The dip Angle of sand dikes ranged from 52°to 90°,with an averageof 75.4°(250 sand dikes were taken as examples),and more than 96%of sand dikes had steep dip Angle(inclination>60°).The Hami sand dikes are convex in both plane and section,but are flat and even grooved insome places due to flood erosion.The protrusion height of hami sand dikes is generally 2~3 cm~5~6 cm,andthe maximum is 10 cm.The experimental results show that under the condition of salt water concentration of 23%and 9%~17%,the shear stress inside sand dikes can be greatly reduced by salt solution,which is 52.63%~85.20%and 12.51%~21.58%,respectively,which is conducive to the formation of sand dikes by seismicliquefaction and fluidization.An unusual assemblage of

关 键 词：砂脉 液化 盐溶活化 流化 地震 哈密 

分 类 号：TU435[建筑科学—岩土工程]