路基支挡结构地震动力响应及抗震设计改进技术研究

发布时间：2018-07-14 13:40

【摘要】：近年来发生在我国的几次大地震造成了震区路基支挡工程的大量破坏,引发了人们对生命线工程的严重担忧。路基支挡工程在地震作用下的破坏模式、震后修复措施及其抗震技术,已成为当前研究的热点和难点问题。本文利用汶川地震路基支挡结构的实震资料,通过采用大型振动台模型试验、数值模拟以及解析计算,研究了地震作用下柔性挡墙和刚性挡墙的动力响应特性和变形破坏机制,以及锚固边坡的地震稳定性影响因素等,并针对加筋土挡墙和格宾挡墙提出了抗震设计改进方法和措施。本文的主要工作及研究结论如下：(1)倾覆破坏是路肩墙在地震作用下的主要破坏模式,提高路肩墙抗倾覆稳定性应是其抗震设计的核心；路堑墙被毁虽会造成道路被掩埋,但经清理后即可恢复通车,总体上看其震害较轻。挡墙的震害受多种因素的影响,挡墙的砌筑方法是影响其震害程度的主要内在因素,地震烈度则是影响挡墙震害程度的主要外部因素,另外,道路线形和断裂带走向也有重要影响。应用地质雷达对震后挡墙进行检测,操作简便检测效率高,且对线路运营不造成任何影响,通过连续的雷达图像可快速准确地判断挡墙的震损状况。(2)利用汶川地震丰富的近场实震资料,分析总结了地震作用下挡墙的变形破坏模式,指出地基类型对挡墙的变形模式有着直接的影响。倾斜变形和推移变形分别是岩质地基挡墙和土质地基挡墙最主要的变形模式。基于Winkler地基模型,认为土体是一系列弹簧和理想刚塑性体的组合体,分析得到了不同变形模式下挡墙地震主动土压力的分布规律。结果表明：挡墙的地震土压力分布特征与变形模式密切相关,除了平行推移模式,其余变形模式下挡墙地震土压力沿墙高都呈非线性分布；岩质地基挡墙的地震土压力合力作用点要比土质地基挡墙高。通过开展位于岩质地基和土质地基上挡墙的振动台模型试验,对文中提出的挡墙地震土压力计算方法进行了验证,发现试验结果和理论分析结果较相吻合(3)为研究填料性质对挡墙地震动力特性的影响,开展了不同填料的挡墙振动台试验,结果发现填料性质对挡墙的动力特性及变形破坏机制影响显著。由于碎石土容易压实,地震波动力作用可较为直接地作用于墙背,故地震土压力要比石英砂挡墙以及风化花岗岩挡墙都大；地震土压力合力作用点也与填料性质密切相关,碎石土填料挡墙的合力作用点高于0.33倍墙高,且随着PGA的增加,合力作用点高度也随之升高；在地震土压力和作用点高度的综合影响下,碎石土挡墙的抗倾覆安全系数小于风化花岗岩和石英砂挡墙,汶川震区挡墙多倾覆破坏,验证了上述结论。采用数值模拟对试验结果进行了验证,认为碎石土填料挡墙的动位移较另外两种填料的挡墙都小。(4)为分析比较条带式和包裹式加筋土挡墙的地震动力响应特征,开展了以上两种加筋土挡墙模型的大型振动台试验。结合震害调查的结果,发现砌块式加筋土挡墙在地震作用下的破坏模式主要表现为局部砌块的松动变形,很少会出现整体垮塌的情况。相比条带式加筋土挡墙,包裹式加筋土挡墙在地震作用下产生的变形量要小。在相同地震动量级作用下,包裹式加筋土挡墙相应部位的水平加速度放大系数要小于条带式加筋土挡墙,但峰值动土压力却要比条带式加筋土挡墙大,这是因为包裹式加筋土挡墙面板在地震作用下的变形量小,对土体的约束能力强所致。因此,在抗震设防区,特别是在高地震烈度区进行加筋土挡墙的选型时,包裹式加筋土挡墙应作为一种优选结构。分析认为加筋土挡墙在进行抗震设计时除了要进行稳定性的检算外,还应检算墙体的变形量,加筋土挡墙在地震作用下的最大变形量应小于允许的变形量。为维持线路的正常使用,加筋土挡墙的变形指数应控制在4%以内。若验算得到的变形量超出允许值,可采取增大墙后填土的压实度和适当增加拉筋长度,以及加厚墙体和降低墙体坡率等措施。(5)为研究柔性挡墙的地震动力响应特性及变形特征,开展了格宾加筋挡墙与生态加筋挡墙的大型振动台模型试验。结果表明：在地震作用下,两种柔性挡墙的峰值动土压力沿墙高呈现中间小两端大的分布特征。鼓胀变形是地震作用下两种挡墙的主要变形模式,变形后挡墙的地震土压力将会有一定程度的衰减。对于铁路及高等级公路柔性挡墙的抗震设计,除要保证其整体稳定性外,还需控制墙体的局部变形量,采用易压实的填料或增加墙体材料的弹性模量和厚度均可以有效控制挡墙的地震变形量。施加受力撑可有效减小格宾网箱的变形,尤其是施加交叉斜撑后变形量的减小最为显著,因此,建议对于变形控制异常严格的高等级道路,可采用该方法来控制格宾挡墙的变形量。(6)现场调研发现,对于锚固工程,锚索的抗震能力最为突出,其次为锚杆,并且认为决定锚杆(锚索)抗震效果的主要因素为锚固长度。挂网喷射混凝土具有一定的抗震能力,而主动网则几乎不具备抗震能力。通过采用拟静力法对汶川震区内锚杆支护边坡的地震稳定性进行验算后得知,边坡的动力安全系数随锚杆长度的增加而增大。利用数值方法分析了地震作用下锚杆支护边坡的动力响应特征以及锚固参数的影响规律。结果表明,锚固措施对边坡的PGA放大系数有明显的抑制作用,地震作用下锚固边坡边坡最大水平位移出现在坡顶,锚杆的轴力也要比静力工况下大;坡面PGA放大系数和最大位移随锚杆长度的增大而减小,随锚杆间距的减小而增大,锚杆倾角对边坡PGA放大系数的影响规律并不明显。
[Abstract]:Several major earthquakes in China in recent years have caused a lot of damage to the subgrade support project in the earthquake area, causing serious concern for the lifeline engineering. The failure mode of the subgrade retaining engineering under the earthquake action, the post earthquake repair measures and the seismic technology have become the hot and difficult problems in the research. This paper uses the Wenchuan earthquake. By using large vibration table model test, numerical simulation and analytical calculation, the dynamic response characteristics and deformation mechanism of flexible retaining wall and rigid retaining wall under earthquake action, as well as the influence factors of the seismic stability of anchored slope are studied by using large vibration table model test, numerical simulation and analytical calculation, and the reinforced earth retaining wall and the guest retaining wall are put forward. The main work and conclusions of this paper are as follows: (1) the overturning failure is the main failure mode of the shoulder wall under the earthquake action, and the improvement of the anti overturning stability of the shoulder wall should be the core of its seismic design; the destruction of the cutting wall will cause the road to be buried, but it can be restored to traffic after cleaning, overall. The seismic damage of the retaining wall is affected by many factors. The masonry method of the retaining wall is the main internal factor affecting the magnitude of the earthquake damage, and the seismic intensity is the main external factor affecting the degree of the damage to the retaining wall. In addition, the road alignment and the strike of the fault zone also have important influence. It has high efficiency and no effect on line operation, and can quickly and accurately judge the earthquake damage condition of the retaining wall through continuous radar images. (2) the deformation and failure modes of the retaining wall under earthquake action are analyzed and summarized by using the abundant near field earthquake data of Wenchuan earthquake, and it is pointed out that the type of foundation is direct to the deformation mode of the retaining wall. The slope deformation and the bed load deformation are the most important deformation modes of the rock foundation retaining wall and the soil foundation retaining wall respectively. Based on the Winkler foundation model, the soil is considered as a combination of a series of springs and ideal rigid plastic bodies. The distribution of the active earth pressure on the retaining wall under different deformation modes is analyzed. The results show that the retaining wall is the retaining wall. The distribution characteristics of seismic soil pressure are closely related to the deformation model. In addition to the parallel model, the seismic soil pressure of the retaining wall is nonlinear along the wall, and the seismic soil pressure in the rock foundation wall is higher than that of the soil foundation retaining wall. The dynamic platform model test is used to verify the seismic soil pressure calculation method proposed in this paper. It is found that the experimental results are in good agreement with the theoretical analysis results (3) to study the influence of the properties of the filler on the dynamic characteristics of the retaining wall, and the vibration table test of the retaining wall with different fillers is carried out. The results of the dynamic characteristics and changes of the filler properties to the retaining wall are found. The effect of seismic wave dynamic action on the back of the wall is more directly than that of the quartz sand retaining wall and the weathered granite retaining wall. The resultant force of the seismic soil pressure is closely related to the properties of the filler, and the resultant force of the gravel packing retaining wall is more than 0.33 times. The wall height is high, and with the increase of PGA, the point height of the resultant force increases. Under the comprehensive influence of the seismic soil pressure and the height of the action point, the anti overturning safety factor of the gravel soil retaining wall is less than the weathered granite and the quartz sand retaining wall, and the retaining wall in the Wenchuan seismic area is overturned and destroyed. It is proved that the dynamic displacement of the gravel packing retaining wall is smaller than that of the other two kinds of fillers. (4) in order to analyze and compare the seismic dynamic response characteristics of the strip type and the wrapped reinforced earth retaining wall, the large shaking table test of the above two reinforced earth retaining wall models is carried out. The failure mode of the earthquake is mainly manifested in the loosening and deformation of the local block, and the overall collapse is seldom seen. Compared with the strip reinforced earth retaining wall, the deformation of the wrapped reinforced earth retaining wall is smaller under the earthquake action. The horizontal acceleration magnification of the corresponding part of the wrapped reinforced earth retaining wall under the action of the same ground motion The coefficient is less than the strip reinforced earth retaining wall, but the peak dynamic earth pressure is larger than the strip reinforced earth retaining wall. This is due to the small deformation of the reinforced earth retaining wall panel under the earthquake action and the strong restraint to the soil. The wrapped reinforced earth retaining wall should be used as a preferred structure. It is considered that the deformation of the wall should be calculated in addition to the calculation of stability when the reinforced earth retaining wall is designed for seismic design. The maximum deformation of the reinforced earth retaining wall under the earthquake action should be less than that of the allowed deformation. The deformation index should be controlled within 4%. If the calculated deformation amount exceeds the allowable value, the compaction degree of the backfill and the length of the reinforced bar, the thickening wall and the reduction of the wall slope can be taken. (5) to study the seismic dynamic response characteristics and the deformation characteristics of the flexible retaining wall, the green reinforcement retaining wall and the ecological addition are carried out. The large shaking table test of the reinforced retaining wall shows that the peak dynamic pressure of the two kinds of flexible retaining walls is characterized by the large middle and small two ends along the wall under the earthquake action. The bulging deformation is the main deformation mode of the two kinds of retaining walls under the earthquake action, and the seismic soil pressure of the retaining wall will be attenuated to a certain extent after the deformation. The seismic design of the flexible retaining wall of road and high grade highway, in addition to ensuring its overall stability, also needs to control the local deformation of the wall, and the elastic modulus and thickness of the wall material can effectively control the deformation of the retaining wall, and the deformation of the bin can be effectively reduced by exerting force support, especially in the application. It is suggested that this method can be used to control the deformation of the bin retaining wall. (6) it is found that the seismic capacity of the anchorage cable is the most prominent, the next is the anchor, and the aseismic effect of the anchor (Anchorage) is decided. The main factor is the anchorage length. The shotcrete has a certain seismic capacity, while the active network has almost no seismic capacity. By using the pseudo static method, the seismic stability of the bolting slope in Wenchuan earthquake area is checked, and the dynamic safety factor of the slope is increased with the increase of the anchor length. The dynamic response characteristics of the anchorage slope under the earthquake action and the influence of anchorage parameters are analyzed. The results show that the anchorage measures have obvious restraining effect on the PGA amplification factor of the slope. The maximum horizontal displacement of the slope of the anchorage slope appears on the top of the slope under the earthquake action, and the axial force of the anchor rod is also larger than that under the static condition; the slope surface is placed on the slope of PGA. The large coefficient and maximum displacement decrease with the increase of anchor length, and increase with the decrease of anchor spacing. The influence of anchor angle on the PGA magnification coefficient of slope is not obvious.
【学位授予单位】：西南交通大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：U416.1

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