摘要
边坡临界滑动场理论已成功的解决了边坡和土压力的相关问题,但折线挡土墙和有地震荷载作用下的土压力的计算研究还未涉及到,本文是对临界滑动场理论的推广和拓展,研究了折线挡土墙和地震作用下的土压力计算。研究内容和结论如下:
本文研究了上下墙体高度比以及上下墙体转角对折线挡土墙土压力的影响;并通过对影响地震土压力的众多因素的研究,得出一些对工程设计有一定参考价值的结论。
对折线挡土墙来说,优化的上下墙体高度比应结合挡土墙的主动土压力大小和其相应的抗倾覆安全系数等因素综合确定,据本文算例的计算结果看,其优化比值应在1左右为宜。同时我们在考虑到其他因素之后,可以尽量减小上墙转角,增大下墙转角,来达到降低上下墙土压力的目的,进而可以降低建造挡土墙的成本。
对地震土压力来说,基于临界滑动场理论的地震土压力计算方法是应用M-O法的基本假设,并克服了M-O法的不足之处(如不能考虑有粘聚力的影响),同时计算结果与M-O法很接近,通过对影响地震土压力的众多因素的研究可得到以下结论:水平地震系数对地震土压力影响较大,而竖向地震系数对地震土压力影响较小,同时竖向地震系数越大,地震土压力越小,所以,有的规范忽略了竖向地震作用的影响,这样偏于安全考虑。当土体的内摩擦角增加时,或粘聚力增大时,地震土压力减小,鉴于此,我们在选择挡土墙墙后填土的类型时,我们应考虑选择内摩擦角大的粘性土。
Critical slip field method has successfully solved the problem of the calculation of slope stability,but the calculation and research of earth pressure under seismic load as well as broken line retaining wall are not involved. This article is the promotion and development of critical slip field method to study the calculation of earth pressure under seismic load as well as broken line retaining wall. Contents and conclusions are as follows:
The earth pressure of retaining wall, which is influenced by ratios between upper and lower wall height as well as their wall corner, is discussed. what's more, by means of studying many factors which influence the seismic earth pressure, some valuable conclusions on engineering are obtained.
Considering the broken line retaining wall, optimization of the height ratio between the upper and lower wall should consider the size of active earth pressure on retaining walls and its corresponding overturning safety factor. According to the calculating results of the example in this article, the appropriate optimal ratio should be around 1.Considering other factors, in order to reduce the upper and lower wall earth pressure we can reduce the corner of upper wall as much as possible and increase the lower wall corner correspondingly.Thereby we can reduce the constructing cost of the retaining wall.
As regard the earth pressure under seismic load, the method of calculation of seismic earth pressure basing on the critical slip field theory have utilized the basic assumptions of Monobe Okabe method.What is more, it overcomes the deficiency of the Monobe Okabe method. (not involving the impact of cohesion),meanwhile the calculating result approximates the result of the Monobe Okabe method. we can calculate by considering various factors affecting seismic earth pressure. The horizontal seismic coefficient has a major impact on the seismic earth pressure rather than the vertical seismic coefficient, meanwhile, with the increasing of the vertical seismic coefficient, the seismic earth pressure reduce correspondingly.Some criterions ignore the impact of vertical seismic load, the result is safer. When the earth internal friction angle or soil cohesion increases,the seismic earth pressure decreases correspondingly.Considering these, we should choose the soil with big internal friction angle while selecting the type of filling behind the retaining wall.
引文
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