NUMERICAL SIMULATION OF INFLUENCING FACTORS OF SURFACE RUPTURE IN OVERLYING SOIL LAYER OF THRUST FAULT

doi:10.3969/j.issn.0253-4967.2023.05.010

Abstract

Abstract:

When the strong earthquakes occur, the deformation and rupture of overlying soil caused by the dislocation of focal faults is one of the important reason for the destruction of ground structures. In the process of a strong earthquake or large earthquake, the deformation reaction and failure of the overlying soil of underground concealed faults are very complicated. To study and analyze the characteristics and influencing factors of surface deformation and fracture of the overlying soil layer, in this paper, the influences of fault dip Angle, fault displacement, and overlying soil thickness on surface deformation and fracture of overlying soil are analyzed by the finite element numerical simulation method comprehensively. The results show that: 1)With the increase of fault vertical dislocation of 1m to 4m, the surface equivalent strain gradually increases, the surface rupture is more likely to occur, and the surface rupture width also wider. With the increase of the thickness of the overlying soil layer from 20m to 60m, and the increase of the fault inclination from 30°, 45°, 70° to nearly 90°, the surface equivalent strain is gradually smaller, the surface rupture is more likely to occur, and the surface fracture width becomes smaller, which means that the amount of dislocation required for the same rupture state needs to increase. 2)When the vertical dislocation of the fault is about 3.3%for the thickness of the overlying soil, the surface rupture occurs only as the fault dip angle is 30°, no surface rupture occurs as the dip angle is 45° and 70°. When the vertical dislocation of the fault is about 5% of the thickness of the overlying soil, the surface rupture occurs only as the fault dip angle is 30° and 45°, no surface rupture occurs as the dip angle is 70° and approaching 90°. When the vertical dislocation of the fault is about 6.6% of the thickness of the overlying soil, the surface rupture occurs as the fault dip angle is 30°、 45° and 70°, and surface rupture is expected to occur as the dip angle is approaching 90°. When the vertical dislocation of the fault is about 10% of the thickness of the overlying soil, the surface rupture occurs as the fault dip angle is 30°, 45°, 60°and approaching 90°. 3)When the amount of vertical dislocation and the thickness of the overlying soil are certain, the ratio of surface rupture width between the hanging wall and footwall which is less affected by fault dip ranges from 3︰1 to 3︰2~1︰1 with the increase of fault dip Angle from 30°, 45° to 70°. When the fault inclination Angle is 30°, with a decrease of vertical dislocation of 4m to 1m, or the increase of overlying soil layer thickness of 20m to 60m, the ratio of surface rupture width between hanging wall and footwall is slightly larger from about 3︰1. When the fault inclination Angle is 45°, with the decrease of vertical dislocation of 4m to 1m, or the increase of overlying soil layer thickness of 20m to 60m, the ratio of surface rupture width between hanging wall and footwall is slightly larger from about 2︰1. When the fault inclination Angle is 75°, with the decrease of vertical dislocation of 4m to 1m, or the increase of overlying soil layer thickness of 20m to 60m, the ratio of surface rupture width between hanging wall and footwall is slightly larger from about 3︰2~1︰1. Under the above fault dip conditions, the ratio of surface rupture width between hanging wall and footwall is less affected by the amount of vertical dislocation and the thickness of overlying soil. As the inclination is approaching 90°, the ratio of surface rupture width between the hanging wall and footwall is about 1︰1, which is not affected by the vertical dislocation and the thickness of the overlying soil layer. 4)The deformation and fracture of the overlying soil layer first began with the soil fracture at the interface of the fault bedrock and soil. With the increase in the amount of dislocation, a fracture point appeared on the surface when the fault dip Angle was 30°, 45°, and 70°. However, when the dip Angle of the fault was close to 90°, there were two initial rupture points on the surface. With the increase of vertical dislocation or the decrease of the overlying soil layer thickness, the overlying soil layer through fracture is finally formed.

Key words: Numerical simulation, thrust fault, overlying soil failure, fault dip angle, vertical dislocation quantity, equivalent effective strain

摘要：

强震发生时, 震源断层错动引发上覆土体变形破裂是地面建(构)筑物破坏的重要原因。为研究和分析上覆土层地表变形与破裂特征及其影响因素, 文中通过有限元数值模拟方法, 综合分析断层倾角、断层错动位移量、上覆土层厚度对上覆土层地表变形与破裂的影响及其规律。结果表明: 1)断层垂直位错量为上覆土层厚度的3.3%、倾角仅为30°时, 发生地表破裂; 断层垂直位错量为上覆土层厚度的5%、倾角为30°、 45°时, 发生地表破裂; 断层垂直位错量为上覆土层厚度的6.6%、倾角为30°、 45°、 70°时, 发生地表破裂; 断层垂直位错量为上覆土层厚度的10%、倾角为30°、 45°、 70°与逼近90°时, 均发生地表破裂。2)随垂直位错量的增加或上覆土层厚度与断层倾角的减小, 地表等效应变逐渐变大, 越容易发生地表破裂。3)随着断层倾角由30°、 45°增加至70°, 上、下盘地表破裂宽度比值从约3︰1增加至3︰2~1︰1。4)上覆土层的变形与破裂, 首先始于断层基岩与土体交界面的土体破裂, 随着位错量的增加, 当断层倾角为30°、 45°、 70°时, 地表均出现了1个初始破裂点; 当断层倾角逼近90°时, 地表出现了2个初始破裂点, 最后上覆土层出现贯通破裂。

关键词: 数值模拟, 逆断层, 上覆土层地表破裂, 断层倾角, 垂直位错量, 等效有效应变

GUO Ting-ting, XU Xi-wei, YUAN Ren-mao, YANG Hong-zhi. NUMERICAL SIMULATION OF INFLUENCING FACTORS OF SURFACE RUPTURE IN OVERLYING SOIL LAYER OF THRUST FAULT[J]. SEISMOLOGY AND GEOLOGY, 2023, 45(5): 1200-1218.

郭婷婷, 徐锡伟, 袁仁茂, 杨宏智. 逆断层上覆土层地表破裂影响因素的数值模拟[J]. 地震地质, 2023, 45(5): 1200-1218.

Figures/Tables 20

Fig. 1 The trench profile near Cement Plant at Xiaoyudong Town(RAN Yong-kang et al., 2008).

Table 1 Parameter table of bedrock and geotechnical materials of the model

类型	材料名称	弹性模量/Mpa	泊松比	容重/kN·m^-3	黏聚力/MPa	摩擦角/(°)
基岩	泥质灰岩	2.0×10⁴	0.2	23	0.15	30
上覆土层	第四纪冲洪积层	1.5×10²	0.35	19	2.5×10^-2	15

Fig. 2 Geometric models establishment and mesh division(taking 2m-40m-30° as an example).

Table 2 Calculation condition table

工况序号	垂直位错量 /m	上覆土层厚度 /m	断层倾角 /(°)	工况序号	垂直位错量 /m	上覆土层厚度 /m	断层倾角 /(°)
1	1	20	30	16	2	60	30
2	1	20	45	17	2	60	45
3	1	20	70	18	2	60	70
4	1	40	30	19	4	20	30
5	1	40	45	20	4	20	45
6	1	40	70	21	4	20	70
7	1	60	30	22	4	40	30
8	1	60	45	23	4	40	45
9	1	60	70	24	4	40	70
10	2	20	30	25	4	60	30
11	2	20	45	26	4	60	45
12	2	20	70	27	4	60	70
13	2	40	30	28	2	40	近90
14	2	40	45	29	4	60	近90
15	2	40	70	30	4	40	近90

Fig. 3 Deformation cloud map of overlying soil(2m-40m-30°).

Fig. 4 Deformation cloud map before and after deformation of overlying soil layer (2m-40m-30°, 4-fold magnification).

Fig. 5 Horizontal displacement distribution of nodes in overlying soil(2m-40m-30°; unit:mm).

Fig. 6 Vertical displacement distribution of nodes in overlying soil(2m-40m-30°, unit:mm).

Fig. 7 Total displacement distribution of nodes in overlying soil(2m-40m-30°, unit:mm).

Fig. 8 The equivalent strain distribution of nodes in overlying soil(2m-40m-30°).

Fig. 9 Comparison of equivalent strain distribution of overlying soil layer under different vertical dislocation of faults((1m, 2m, 4m)-20m-30°).

Fig. 10 Comparison of equivalent strain distribution of overlying soil layer under different vertical dislocation of faults((1m, 2m, 4m)-20m-45°).

Fig. 11 Comparison of equivalent strain distribution of overlying soil layer under different vertical dislocation of faults((1m, 2m, 4m)-20m-70°).

Fig. 12 Comparison of equivalent strain distribution of overlying soil layer under different overlying thicknesses(2m-(20m, 40m, 60m)-30°).

Fig. 13 Comparison of equivalent strain distribution of overlying soil layer under different overlying thicknesses(2m-(20m, 40m, 60m)-45°).

Fig. 14 Comparison of equivalent strain distribution of overlying soil layer under different overlying thicknesses(2m-(20m, 40m, 60m)-70°).

Fig. 15 Comparison of equivalent strain distribution of overlying soil layer under different fault dip angles(2m-20m-(30°, 45°, 70°)).

Fig. 16 Comparison of equivalent strain distribution of overlying soil layer under different fault dip angles(2m-40m-(30°, 45°, 70°)).

Fig. 17 Comparison of equivalent strain distribution of overlying soil layer under different fault dip angles(2m-60m-(30°, 45°, 70°)).

Fig. 18 Comparison of equivalent strain distribution of overlying soil layer under the condition of fault dip approaching 90°.

References 25

[1]	《工程地质手册》编写委员会. 2018. 工程地质手册[M]. 北京: 中国建筑工业出版社.
	Editorial Committee of Geological Engineering Handbook. 2018. Geological Engineering Handbook[M]. China Architecture and Building Press, Beijing.
[2]	郭恩栋, 邵光彪, 薄景山, 等. 2002. 覆盖土层场地地震断裂反应分析方法[J]. 地震工程与工程振动, 22(5): 122—126.
	GUO En-dong, SHAO Guang-biao, BO Jing-shan, et al. 2002. A method for earthquake rupture analysis of overlying soil site[J]. Earthquake Engineering and Engineering Vibration, 22(5): 122—126. (in Chinese)
[3]	韩竹军, 冉勇康, 徐锡伟. 2002. 隐伏活断层未来地表破裂带宽度与位错量初步研究[J]. 地震地质, 24(2): 484—492.
	HAN Zhu-jun, RAN Yong-kang, XU Xi-wei. 2002. Primary study on possible width and displacement of future surface rupture zone produced by buried active fault[J]. Seismology and Geology, 24(2): 484—492. (in Chinese)
[4]	胡平, 丁彦慧, 蔡奇鹏, 等. 2011. 第四纪地层中断层同震错动行为的离心机试验研究[J]. 地球物理学报, 54(9): 2293—2301.
	HU Ping, DING Yan-hui, CAI Qi-peng, et al. 2011. Centrifuge modeling on the behavior of co-seismic fault dislocation in the Quaternary stratum[J]. Chinese Journal of Geophysics, 54(9): 2293—2301. (in Chinese)
[5]	黄辉. 2016. 基岩逆断层错动引起的上覆土体变形预测[J]. 工程地质学报, 24(6): 1255—1261.
	HUANG Hui. 2006. Analytical approach for estimating ground deformation profile induced by reverse faulting in overlying soil[J]. Journal of Engineering Geology, 24(6): 1255—1261. (in Chinese)
[6]	李红, 邓志辉, 陈连旺, 等. 2019. 走滑断层地震地表破裂带分布影响因素数值模拟研究: 以1973年炉霍 M_S7.6 地震为例[J]. 地球物理学报, 62(8): 2871—2884.
	LI Hong, DENG Zhi-hui, CHEN Lian-wang, et al. 2019. Simulation study on the influencing factors of surface rupture zone distribution of strike-slip fault: take Luhuo M_S7.6 earthquake in 1973 for example[J]. Chinese Journal of Geophysics, 62(8): 2871—2884. (in Chinese)
[7]	李小军, 赵雷, 李亚琦. 2009. 断层错动引发基岩上覆土层破裂过程模拟[J]. 岩石力学与工程学报, 28(S1): 2703—2707.
	LI Xiao-jun, ZHAO Lei, LI Ya-qi. 2009. Simulation of fault movement induced rupture process of overlaying soil of bedrock[J]Chinese Journal of Rock Mechanics and Engineering, 28(S1): 2703—2707. (in Chinese)
[8]	李勇, 黄润秋, Densmore A L, 等. 2009. 龙门山小鱼洞断裂在汶川地震中的地表破裂及地质意义[J]. 第四纪研究, 29(3): 502—512.
	LI Yong, HUANG Run-qiu, Densmore A L, et al. 2009. Surface rupture of Xiaoyudong Fault caused by Wenchuan earthquake and its geological significance[J]. Quaternary Sciences, 29(3): 502—512. (in Chinese)
[9]	刘守华, 董津城, 徐光明, 等. 2005. 地下断裂对不同土质上覆土层的工程影响[J]. 岩石力学与工程学报, 24(11): 1868—1874.
	LIU Shou-hua, DONG Jin-cheng, XU Guang-ming, et al. 2005. Influence on different overburden soils due to bedrock fracture[J]. Chinese Journal of Rock Mechanics and Engineering, 24(11): 1868—1874. (in Chinese)
[10]	梅海. 2010. 龙门山地区构造应力场及灾害效应数值模拟研究[D]. 西安: 长安大学:1—196.
	MEI Hai. 2010. Numerical simulation of tectonic stress field and disaster effect in Longmenshan area[D]. Chang'an University, Xi'an: 1—196. (in Chinese)
[11]	冉勇康, 陈立春, 陈桂华, 等. 2008. 汶川 M_S8.0 地震发震断裂大地震原地重复现象初析[J]. 地震地质, 30(3): 630—643.
	RAN Yong-kang, CHEN Li-chun, CHEN Gui-hua, et al. 2008. Primary analyses of in-situ recurrence of large earthquake along seismogenic fault of the M_S8.0 Wenchuan earthquake[J]. Seismology and Geology, 30(3): 630—643. (in Chinese)
[12]	四川省地质矿产局. 1997. 四川省岩石地层[M]. 武汉: 中国地质大学出版社.
	Sichuan Provincial Bureau of Geology and Mineral Resources. 1997. Petrostratigraphy in Sichuan Province[M]. China University of Geosciences Press, Wuhan. (in Chinese)
[13]	王鹏, 刘静, 孙杰, 等. 2013. 2008年汶川大地震小鱼洞地表破裂带精细填图[J]. 地质通报, 32(4): 538—562.
	WANG Peng, LIU Jing, SUN Jie, et al. 2013. Detailed mapping of the Xiaoyudong coseismic surface rupture of Wenchuan earthquake[J]. Geological Bulletin of China, 32(4): 538—562. (in Chinese)
[14]	徐锡伟, 郭婷婷, 刘少卓, 等. 2016. 活动断层避让相关问题的讨论[J]. 地震地质, 38(3): 477—502. doi: 10.3969/j.issn.0253-4967.2016.03.001.
	XU Xi-wei, GUO Ting-ting, LIU Shao-zhuo, et al. 2016. Discussion on issues associated with setback distance from active fault[J]. Seismology and Geology, 38(3): 477—502. (in Chinese)
[15]	徐锡伟, 于贵华, 马文涛, 等. 2002. 活断层地震地表破裂 “避让带” 宽度确定的依据与方法[J]. 地震地质, 24(4): 470—483.
	XU Xi-wei, YU Gui-hua, MA Wen-tao, et al. 2002. Evidence and methods for determining the safety distance from the potential earthquake surface rupture on active fault[J]. Seismology and Geology, 24(4): 470—483. (in Chinese)
[16]	于贵华, 徐锡伟, 陈桂华, 等. 2009. 汶川8.0级地震地表变形局部化样式与建筑物破坏特征关系初步研究[J]. 地球物理学报, 52(12): 3027—3041.
	YU Gui-hua, XU Xi-wei, CHEN Gui-hua, et al. 2009. Relationship between the localization of earthquake surface ruptures and building damages associated with the Wenchuan 8.0 earthquake[J]. Chinese Journal of Geophysics, 52(12): 3027—3041. (in Chinese)
[17]	赵雷, 李小军, 霍达. 2006. 有软夹层的基岩上覆土层在断层错动时的破裂特征研究[J]. 地震学报, 28(5): 523—528.
	ZHAO Lei, LI Xiao-jun, HUO Da. 2006. Study on the rupture characteristics of the overlaying soil with soft interlayer due to fault bedrock dislocation[J]. Acta Seismologica Sinica, 28(5): 523—528. (in Chinese)
[18]	周庆, 周本刚, 冉洪流. 2006. 不同土质条件下断层地表破裂对比研究[J]. 震灾防御技术, 1(3): 225—233.
	ZHOU Qing, ZHOU Ben-gang, RAN Hong-liu. 2006. Comparative study on surface rupture of faults in different soil mass[J]. Technology for Earthquake Disaster Prevention, 1(3): 225—233. (in Chinese)
[19]	Anastasopoulos I, Gazetas G, Bransby M F, et al. 2007. Fault rupture propagation through sand: finite-element analysis and validation through centrifuge experiments[J]. Journal of Geotechnical & Geoenvironmental Engineering, 133(8): 943—958.
[20]	Bray J D. 2009. Designing buildings to accommodate earthquake surface fault rupture[C]// USA: ATC & SEI Conference on Improving the Seismic Performance of Existing Buildings and Other Structures: 1—12.
[21]	Cole D A, Lade P V. 1984. Influence zones in alluvium over dip-slip faults[J]. Journal of Geotechnical Engineering, 110(5): 599—616. DOI URL
[22]	Lee J C, Chen Y G, Sieh K, et al. 2001. A vertical exposure of the 1999 surface rupture of the Chelungpu Fault at Wufeng, Western Taiwan: Structural and paleoseismic implications for an active thrust fault[J]. Bulletin of the Seismological Society of America, 91(5): 914—929. DOI URL
[23]	Nurminen F, Boncio P, Visini F, et al. 2020. Probability of occurrence and displacement regression of distributed surface rupturing for reverse earthquakes[J]. Frontiers in Earth Science, 8: 293—306. doi: 10.3389/feart.2020.581605.
[24]	Taniyama H, Watanabe H. 2000. Deformation of sandy deposits by fault movement[C]// Proeedings of the 12th World Conference of Earthquake Engineering. Tokyo: Mc Graw Hill: 1—6.
[25]	Yeats R S, Sieh K, Allen C R. 1997. The geology of earthquakes[M]. New York: Oxford University Press:473—485.