﻿ 强震作用下高填方边坡变形与稳定性研究 Study on Deformation and Stability of High Filled Slopes under Strong Earthquakes

Vol. 11  No. 03 ( 2021 ), Article ID: 41180 , 18 pages
10.12677/AG.2021.113027

Study on Deformation and Stability of High Filled Slopes under Strong Earthquakes

Xinjie Zhao, Chunqing Xie, Kai Pan*, Hang Li

Guangdong China Coal Jiangnan Engineering Survey and Design Co. Ltd., Guangzhou Guangdong

Received: Feb. 20th, 2021; accepted: Mar. 17th, 2021; published: Mar. 24th, 2021

ABSTRACT

Foundation stability under strong earthquakes is one of the key engineering geological issues that restrict construction in high seismic intensity areas. Based on the site seismic conditions, based on the results of the seismic hazard probability analysis, artificially synthesize seismic waves, and establish a finite element numerical calculation model, input artificially synthesized seismic waves, and apply different fill heights, different seismic intensities, and different site conditions to high fill slope The dynamic response under different grading ratios is analyzed, relying on the huge high filling project of the western plateau airport. Results show that the response of the top slope of the fill slope is the most severe, the second is the foot of the slope, the middle is the weakest, and the displacement and acceleration have significant elevation amplification effects. The fill slope has typical characteristics of late instability and failure, and is closely related to groundwater engineering effects, under earthquake. The research results can provide references for similar engineering design, construction, scientific research, disaster prevention and mitigation in areas with high earthquake intensity.

Keywords:Severe Strong Earthquake, High Seismic Intensity, Foundation Stability, Giant High Fill Slope, Ground Motion Response, Groundwater Engineering Effect, Disaster Prevention and Mitigation

1. 引言

2. 高填方边坡的主要震害

2.1. 填方体竖向不均匀沉陷

2.2. 填方边坡开裂、错落、垮塌、滑移

2.3. 填方顶面的隆起、拉裂

2.4. 支挡结构和防护工程的震害

3. 高填方边坡地震动响应特征分析

3.1. 工程概况

Figure 1. Engineering features of ganzi airport in construction

1) 区域地质情况

Figure 2. Geological Structure Outline of Ganzi Airport

2) 工程区地形地貌

Figure 3. Terrain and geomorphic features of the engineering area

3) 工程区岩土特性

3.2. 边坡动力响应时程分析

1) 计算模型的建立

Figure 4. Overall distribution characteristics before filling in the study area

Figure 5. Overall distribution characteristics after filling in the study area

Figure 6. Computational model of rock and soil layering

Table 1. Physical and mechanical parameters of calculation model

2) 地震波的合成

$a\left(t\right)=f\left(t\right)\underset{k=0}{\overset{n}{\sum }}{A}_{k}\mathrm{cos}\left({\omega }_{k}t+{\psi }_{k}\right)$ (式1)

Figure 7. 10% acceleration time history curve

3) 边界条件设定

① 底部边界假定水平和竖直方向均为固定；② 侧向边界由于斜坡体存在自重应力，且自重应力对填方体的固结沉降和斜坡稳定性影响非常大，地震作用下基岩及填方体向后缘无限延伸，水平位移较小，因此假定水平向固定，竖直向自由；③ 顶部边界水平和竖直方向均为自由；④ 阻尼比系数λ = 0.05；⑤ 放坡比1:2.5。

4) 时程计算方案

Figure 8. Ground motion analysis technology route

5) 结果分析

① 地震烈度对边坡变形的影响

Figure 9. Characteristics of permanent deformation of slope with earthquake intensity of 6.5 degrees

Figure 10. Characteristics of permanent deformation of slopes with earthquake intensity of 8.0 degrees

② 边坡不同坡比动力响应分析

A——坡比1:2.5放坡与1:3.0不进行地基处理条件下动力响应对比分析；

B——坡比1:2.5条件下地基处理前后边坡动力响应分析；

C——坡比1:2.5放坡与1:3.0地基处理后动力响应对比分析。

(A) 坡比1:2.5与1:3.0不进行地基处理条件下动力响应对比分析

(B) 坡比1:2.5地基处理前后边坡动力响应分析

Figure 11. Intensity 8.0 Permanent deformation of slope (1:3.0 Gradation)

Figure 12. Characteristics of permanent deformation of slope after foundation treatment (1:3.0 Gradation)

Figure 13. X-direction relative displacement of slope monitoring point before replacement

Figure 14. Relative displacement in X direction of slope monitoring point after replacement

Figure 15. Relative displacement in Y direction of monitoring point of slope surface before replacement

Figure 16. Relative displacement in Y direction of slope monitoring point after replacement

Figure 17. 4# point X-direction peak acceleration

Figure 18. 4# point Y-direction peak acceleration

Figure 19. 6# point X-direction peak acceleration

Figure 20. 6# point Y-direction peak acceleration

(C) 坡比1:2.5与1:3.0地基处理后边坡动力响应分析

1:2.5放坡地基处理后坡顶4号监测点X向最大相对位移0.278 m，Y向最大相对位移0.156 m，边坡永久变形量0.289 m；1:3.0放坡地基处理后X向最大相对位移0.266 m，Y向最大相对位移0.178 m，边坡永久变形量0.292 m。初步得出，增大放坡坡比后结合进行地基处理对减小边坡X向永久位移有效，对减小Y向永久作用不明显。6号、8号监测点显示增大坡比并进行地基处理对减小边坡Y向永久位移具有一定效果，但对减小X向永久位移效果不明显。

③ 坡脚反压对边坡动力响应的影响

Figure 21. 1:3.0 Characteristics of permanent deformation of slope foot anti-pressure slope

Table 2. Changes in peak acceleration at slope monitoring points before and after backpressure

④ 边坡的位移及加速度高程放大效应特征

Table 3. Statistics of ground motion response data at vertical monitoring points on slope tops

${H}_{dx}=0.0496{x}^{0.3901}$ (2)

${S}_{dy}=0.026{x}^{0.4244}$ (3)

X向加速度与垂向填方高度的关系函数：

${A}_{x}=9e-0.5{x}^{2}-0.0052x+0.5158$ (4)

Figure 22. Relation curve between vertical fill height and X relative displacement

Figure 23. Relation curve between vertical fill height and Y relative displacement

Table 4. Data statistics of calculation results of ground motions on slope surface monitoring points

Figure 24. Relationship between slope height and relative displacement in X direction

Figure 25. Relationship between slope height and relative displacement in Y direction

Figure 26. Relationship between slope height and X-direction acceleration

Figure 27. Relationship between slope height and Y-direction acceleration

${H}_{fx}=0.0022x+0.0568$ (5)

X向加速度与边坡高度的关系函数：

${S}_{fx}=5e-06{x}^{2}+0.0007x+0.026$ (6)

4. 震后失稳机制与地下水工程效应

Figure 28. Variation curve of super-pore water pressure under earthquake

5. 结论

1) 高地震烈度区高填方边坡地震动响应特征：① 边坡中上部地震动效应大于中下部地震动响应，坡面上部1/3至坡顶的地震动响应最剧烈；② 顶部表现出越靠近临空面地震动越强烈，向后缘延伸地震动响应逐步减弱；③ 坡体内部地震效应较弱，越靠近表面地震动响应越强烈，建设中应进行重点加强抗震设计和边坡加固工作。

2) 地基不均会产生地震波的差异性放大作用，导致坡体沉降、开裂、滑塌破坏，加剧震害。建议在填方过程中应对不均匀地基进行处理，特别是边坡部位，应重点处理以确保边坡的稳定。

3) 地震后边坡土石松动开裂，为雨水的入渗创造了条件，从而导致边坡内部地下水径流路径发生变化，降低岩土体力学强度，加速地下水渗流潜蚀，易造成震后失稳，震后应及时采取有效应的应急处置措施。

4) 地下水具有浸泡软化填方地基土，劣化岩土物理力学性能，渗流潜蚀破坏填筑体的工程效应，并且强震作用产生的高孔隙水压力和超孔隙水压力将进一步加剧边坡的变形、破坏。

Study on Deformation and Stability of High Filled Slopes under Strong Earthquakes[J]. 地球科学前沿, 2021, 11(03): 305-322. https://doi.org/10.12677/AG.2021.113027

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18. NOTES

*通讯作者。