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1、 基坑开挖论文：软岩深基坑爆破开挖的边坡稳定性分析【中文摘要】爆破方法开挖岩质深基坑已在交通、水利水电和国防工程等领域得到广泛应用,爆破过程中不可避免地产生的地震效应对开挖边坡稳定性的影响问题一直受到岩土工程界和工程爆破界的关注,特别是在软岩深基坑爆破开挖工程中尤为重要。为此,一方面需要研究爆破振动控制技术,另一方面必须正确分析爆破动力作用下工程边坡的稳定性,才能达到既能保证施工安全、又能提高施工进度与工程效益的。因此,进行软岩深基坑爆破开挖的边坡稳定性分析具有重要的理论价值和社会意义。论文以南溪长江大桥北岸重力式锚碇软岩深基坑爆破开挖工程为背景,采用现场试验、数理统计和数值模拟等方法进行软岩
2、深基坑爆破开挖的边坡稳定分析研究,从动、静力学角度分析了多种工况下深基坑高边坡的稳定性,其研究工作和成果主要体现在如下几个方面。根据现场工程地质条件,结合软岩深基坑的结构特点及设计要求,提出了深基坑开挖爆破方案,并对爆破方案的地震效应进行了现场试验。试验研究结果表明,开挖爆破在基坑内及其周边产生的垂直向振动速度峰值大于水平向质点振动速度峰值；同段起爆的装药量是控制爆破振动强度的关键参数；通过统计分析,给出了基坑开挖爆破的地震波衰减公式。以基坑北侧高边坡为计算分析对象,选取典型断面建立三维数值模型,通过极限平衡法和FLAC3D对基坑高边坡在天然状态和降雨条件下的稳定性进行了分析。计算结果表明,基
3、坑高边坡在开挖后基本稳定,但第二级土坡坡脚产生较大的水平位移,且有两条潜在滑带；在降雨条件下,数值计算不收敛,安全系数下降了14.8%。利用现场实测振动速度作为边坡动荷载的输入,分析了爆破荷载下边坡的位移及速度等动态响应特征,在重复爆破荷载作用下北侧第二级土质边坡坡脚处产生累积的永久位移。此外,通过计算值与实测值的对比分析,证明FLAC3D用于进行爆破作用下边坡动态响应的数值模拟是可行的。为改进爆破方案和采取支护措施提供依据。结合工程实际支护形式对基坑支护后的北侧高边坡进行FLAC3D数值模拟,对边坡的锚杆支护效果进行评价。分析了多种工况下支护边坡的受力状态及其稳定性,计算结果与实际开挖过程中
4、由于降雨和爆破作用下基坑边坡软弱层的局部垮塌情况一致,并给出了避免基坑边坡发生类似垮塌的技术措施。【英文摘要】Blasting method in the deep foundation pit excavation has already been widely applied in transportation, water conservancy, hydropower and defense engineering and other fields. By this way, blasting seismic effect is inevitable. The influence of
5、 seismic effect on the slope stability has drawn great attention in geotechnical engineering and blasting engineering. It is especially important in blasting excavation engineering of soft rock deep foundation pit. Therefore, on the one hand, we need to study the control technology of blasting vibra
6、tion, on the other hand, we must correctly analyze the stability of the slope under the blasting effect to guarantee the project safety and improve the progress and benefits of engineering. Therefore, it has important theoretical value and social significance to carry out the slope stability analysi
7、s of the soft rock blasting excavation of the deep foundation pit.Taking the gravity type anchor ingot pit excavation of Nanxi Yangtze River Bridge as a specific example, the in-situ test, mathematical statistics, and numerical simulation methods are used in the slope stability analysis of blasting
8、excavation of the deep foundation pit, and the dynamic and static stability analyses of deep foundation pit high slope under various conditions are carried out. The research work and achievement are mainly embodied in the following aspects.Based on the engineering geology, combined with the structur
9、e characteristics and the design requirements of the soft rock deep pit, the blasting excavation scheme of the deep pit is proposed. In the process of bedrock excavation, blasting vibration test is conducted, while on-site blasting data is monitored. Test results show that the vertical peak vibratio
10、n velocity is higher than the horizontal peak vibration velocity in the foundation pit excavation. The blasting charge in the same period is the key parameter to control blasting vibration. Through the statistical analysis, the seismic wave attenuation formulas of the excavation blasting are deduced
11、.The typical section of northern pit slope is selected to set up 3-D numerical model. Through the limit equilibrium method and FLAC3D, stability of foundation pit slope in natural state and rainfall condition is analyzed. The results show that high slope after excavation keeps the basic stability. B
12、ut the second soil slope toe has larger horizontal displacement, and two potential sliding zones turn up. In the rainfall condition, the numerical calculation fails to converge, and the safety factor declines 17%.Taking the in-situ measured vibration data as input loads, the dynamic response charact
13、eristics of displacement and speed in the slope under blasting loads are explored. Repeated blasting loads result in cumulate permanent displacement in the second soil slope toe. Through the comparative analysis in the calculated and the measured values, the result shows that FLAC3D is feasible for
14、numerical simulation of dynamic response in the slope under the blasting. The results can provide the basis for improving blasting scheme and taking-support measures.Based on the supporting structures which are actually used in the foundation pit, the reinforced pit slope is simulated by FLAC3D. The
15、 effect of the bolt supporting in the slope is evaluated. The stability of the reinforced slope and the bearing forces of retaining structure under different conditions are studied. Calculation results are consistent with actual partial collapse in the process of foundation pit slope excavation due
16、to heavy rains and repeated excavation blasting. Several suggestions are offered to prevent these kinds of collapse accidence.【关键词】基坑开挖 爆破振动 边坡稳定 FLAC3D 锚杆支护【英文关键词】foundation pit excavation blasting vibration slope stability FLAC3D bolting support【目录】软岩深基坑爆破开挖的边坡稳定性分析摘要6-7Abstract7-8第1章 绪论12-171.1 课
17、题研究背景及意义12-131.2 国内研究现状13-161.2.1 爆破振动效应研究现状131.2.2 爆破振动对边坡稳定性影响研究现状13-151.2.3 支护边坡动力稳定性研究现状15-161.3 本文研究目标、内容及技术路线16-171.3.1 研究目标161.3.2 研究内容161.3.3 技术路线16-17第2章 基坑工程概况及爆破开挖方案17-252.1 大桥概况172.2 工程地质条件17-202.2.1 地形地貌17-182.2.2 地层岩性18-192.2.3 地质构造192.2.4 水文地质条件19-202.3 锚碇基坑爆破开挖方案20-252.3.1 开挖区工程特点20-
18、212.3.2 分层开挖爆破的顺序21-222.3.3 浅孔台阶爆破方案设计22-25第3章 基坑开挖爆破振动测试及结果分析25-353.1 爆破振动测试25-263.1.1 爆破振动效应253.1.2 爆破振动测试原理25-263.2 测试方法简介26-283.2.1 测试系统26-273.2.2 测点的布置27-283.3 爆破振动测试结果与分析28-323.3.1 测试结果28-303.3.2 振动规律分析30-323.3.3 药量控制323.4 爆破振动效应的控制措施32-333.5 本章小节33-35第4章 基坑开挖北侧高边坡稳定性分析35-584.1 概述35-374.2 FLAC
19、(3D)数值分析37-414.2.1 FLAC(3D)程序简介374.2.2 强度折减法37-384.2.3 数值模型的建立38-414.2.4 计算步骤及方案414.3 静力条件下开挖边坡的稳定性分析41-474.3.1 天然状态下开挖边坡模拟41-434.3.2 降雨条件下开挖边坡模拟43-454.3.3 开挖边坡极限平衡分析45-474.4 爆破荷载作用下开挖边坡的稳定性分析47-564.4.1 爆破开挖第三级边坡动力响应48-524.4.2 爆破开挖第四级边坡动力响应52-544.4.3 基于拟静力法的动力稳定性分析54-564.5 本章小结56-58第5章 基坑支护边坡稳定性与支护效
20、果评价58-775.1 基坑支护概述58-615.1.1 基坑支护方案58-605.1.2 FLAC(3D)锚杆计算模型60-615.2 支护边坡的静力稳定性分析61-685.2.1 天然状态下支护边坡模拟61-655.2.2 降雨条件下支护边坡模拟65-675.2.3 支护边坡极限平衡分析67-685.3 爆破荷载作用下支护边坡的稳定性分析68-725.3.1 基坑边坡动力响应695.3.2 锚杆支护动力响应69-725.3.3 基于拟静力法的支护边坡动力稳定性分析725.4 基坑边坡现场局部垮塌情况72-755.4.1 垮塌情况72-745.4.2 原因分析745.4.3 处理方法74-755.5 本章小结75-77结论与展望77-79结论77-78展望78-79致谢79-80参考文献80-83