冲击荷载对病害库岸挡墙的稳定性影响研究

发布时间：2018-03-31 04:30

本文选题：库岸病害挡墙　切入点：冲击荷载　出处：《重庆交通大学》2017年硕士论文

【摘要】：三峡成库蓄水后,库岸挡墙受水位变动影响,墙后土体强度降低,影响其稳定性,出现了较多病害库岸挡墙。板桩结构是常见加固病害挡墙的结构形式,但已有研究更多集中在板桩结构加固病害挡墙的优化方式以及加固之后病害挡墙抵抗变形的效果,较少考虑板桩结构在加固施工过程中对原病害库岸挡墙产生的影响。施工中产生的冲击荷载给周围建筑物带来破坏的例子屡见不鲜,冲击荷载对建筑物的稳定性影响成为日益重视的问题。本文在前人研究的基础上,借助PLAXIS有限元软件分析了5种施工工况下挡墙前方冲孔施工对挡墙的稳定性影响,并对多桩同时施工条件下间距选择对挡墙稳定性影响进行了分析。本文主要工作及取得的成果如下:(1)对被冲击土体的本构模型和冲击荷载峰值计算公式进行讨论分析,确定本文采用的土体本构模型和冲击荷载计算方法。(2)在未破坏前,挡墙抵抗变形的能力随着锤击次数的增加而提高;随着水位的升高,挡墙位移值有先增大后减小的趋势。同时,冲击力峰值和冲击频率的变化也会影响挡墙的位移值。(3)锤击表面土层时对挡墙变形值影响最大,而后随着锤击深度的增加,这种变形影响程度出现大幅度的减小,施工中建议先小冲击能冲孔施工,并重点监测开始冲孔时挡墙的位移变化。随着钢护筒嵌入深度的增加,锤击产生的冲击荷载对挡墙影响越小,其中在钢护筒嵌入风化层时变位值有较大幅度的减小,建议施工中至少使钢护筒嵌入风化层以下,最好直接嵌入中风化层后再冲孔施工。(4)多桩同步施工会较大的增加挡墙位移变形值,施工间距越大,对挡墙的稳定性影响越小,当施工间距增加到8D时(D为桩直径),即跳3根桩施工,再加大施工间距减小挡墙位移值的效果较弱,故实际施工建议施工间距为8D。同时在施工中需要重点监控由于多桩同步施工挡墙的变形量。
[Abstract]:After reservoir storage, the retaining wall of reservoir bank is affected by the change of water level, and the strength of soil behind the wall decreases, which affects the stability of the retaining wall, and many diseases occur. The sheet pile structure is the structural form of the commonly strengthened diseased retaining wall. However, more studies have been focused on the optimization of the reinforcement of the diseased retaining wall and the effect of resisting the deformation of the diseased retaining wall after the reinforcement. Less consideration is given to the influence of sheet pile structure on the original damaged bank retaining wall in the course of strengthening construction. Examples of damage to surrounding buildings caused by impact load in construction are not uncommon. The influence of impact load on the stability of buildings has been paid more and more attention. On the basis of previous studies, this paper analyzes the influence of punch construction on the stability of retaining wall under five construction conditions with the help of PLAXIS finite element software. The influence of spacing selection on the stability of retaining wall under the condition of multi-pile simultaneous construction is analyzed. The main work and results obtained in this paper are as follows: 1) the constitutive model of the affected soil and the formula for calculating the peak value of impact load are discussed and analyzed. It is determined that the soil constitutive model and impact load calculation method adopted in this paper increase the resistance of retaining wall to deformation with the increase of hammer impact times and increase with the increase of water level before failure. At the same time, the change of the peak impact force and the impact frequency will also affect the displacement value of the retaining wall. 3) when hammering the surface soil layer, the deformation value of the retaining wall will be most affected, and then with the increase of the depth of impact, the deformation value of the retaining wall will be greatly affected by the change of the peak impact force and the impact frequency. The influence of this deformation is greatly reduced. In construction, it is suggested that small impact energy should be used to punch holes first, and the displacement of retaining wall should be monitored at the beginning of punching. With the increase of the embedded depth of steel casings, The impact load caused by hammering has less influence on the retaining wall, in which the value of displacement is greatly reduced when the weathering layer is embedded in the steel shield. It is suggested that at least the steel retaining tube be embedded below the weathered layer in construction. It is better to embed the middle weathering layer directly before punching. 4) the simultaneous construction of multiple piles will increase the displacement and deformation value of the retaining wall. The larger the construction distance, the less the influence on the stability of the retaining wall. When the construction spacing is increased to 8D, the pile diameter is increased, that is, three piles are jumped, and the effect of increasing the construction spacing to reduce the displacement of the retaining wall is weak. Therefore, the actual construction distance is 8D. it is necessary to monitor the deformation of retaining wall due to multi-pile synchronous construction.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV697

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