强震区断层带边坡抗滑桩抗震加固机理及模式研究

发布时间：2018-08-03 09:05

【摘要】：受“5.12”汶川大地震影响,我国西南山区发生了大量边坡地质灾害。在强震区进行公路修建的过程中,边坡的稳定性显得尤为重要。在这些不同种类的边坡之中,断层带边坡在地震失稳时具有其自身的特点。经有关学者研究统计,用抗滑桩加固的断层带边坡在地震作用下只有少数发生倾斜变形,大多数的桩基本无变化,并且其加固的边坡都比较稳定。本文基于以上事实选取广甘高速公路断层带边坡为研究对象,运用数值模拟的方法对公路边坡设计中常用的无平台、有平台不同坡高边坡的动力响应规律以及抗滑桩加固机理和加固模式进行了研究,并在此基础上对广甘高速公路断层带边坡进行了抗滑桩动力稳定性分析。通过上述研究获得的主要成果如下： (1)在地震力作用下,断层带边坡越高,坡体水平位移呈线性增长；坡顶、坡面处水平位移增值较大,坡脚、坡底处较小；最大主应力往坡顶和坡面处集中,当坡高达到一定高度时,坡面形成贯通的拉应力带,坡脚产生较明显的应力集中区域。对比分析认为,断层带边坡高度越高,其动力作用下自稳能力越差。记录地震作用不同时间段坡体的水平位移值情况,结果发现,在地震波持续作用下,水平位移值不断增加,边坡发生累积变形。 (2)断层带边坡动力变形分析：由于断层带岩体松散、破碎,地震波在边坡岩土体内传播和作用过程中,坡体内产生的横波和纵波使边坡岩土体不同部位发生相互作用,产生拉张或剪切变形甚至导致边坡岩土体破坏。同时,地震波在传播过程中遇到界面时将发生反射、折射现象,不同地震波还将叠加协同作用,致使岩土体产生拉张变形和剪切变形。 (3)应用FLAC3D软件模拟支护前后坡体动力响应特征,抗滑桩能显著改善边坡坡顶水平位移,约束坡面岩体的变形和破坏；能改善边坡坡顶与坡脚的塑性区分布情况,使边坡应力分布的更加均匀,保证边坡的稳定性。 (4)在地震作用下,记录了桩间土体以及桩内力变化情况。桩顶端要比桩中部变形大,易发生倾斜破坏。桩剪力在地震作用初期已经形成,此后的地震作用只会引起剪力的微小变化。地震作用初期桩弯矩值不大,在零附近波动,随着地震波持续作用,弯矩迅速增加到最大值。桩身弯矩变化特征为自下而上先增加后减少,最大值一般位于桩身中间位置附近。抗滑桩设计时,应在内力最大值附近增设钢筋。 (5)对比分析了有无滑面时抗滑桩动力支护效果。边坡无滑面时桩间土的位移是由坡体内部向临空面逐渐增加,坡体塑性变形区集中在坡面处,坡顶有少部分变形,桩身所受内力值较小；有滑面时桩间土的位移由坡体内部向临空面先增大后减小,边坡覆盖层土体变形很大,在坡顶处存在大量的塑性变形区,边坡土体较容易沿着滑面往临空面方向移动,抗滑桩内力值较大,易发生破坏。值得注意的是,边坡具有滑面时能显著影响桩间土体位移变化情况,在滑面处位移最大。 (6)总结出了抗滑桩对强震区断层带边坡的加固机理：断层带岩体松散、破碎,地震波作用在坡体上产生振荡效应,使岩体在反复的振荡过程中产生松弛进而向临空面滑动。当抗滑桩支护后,它具有挤密作用,改善桩周岩土体；当地震波中的面波从坡体传播到抗滑桩界面时,一部分直接传播在桩身处,另一部分传播在桩土间压力拱处,由压力拱将地震波传播于抗滑桩；地震波中的纵波与横波传播到桩附近时,由于抗滑桩比断层带岩体弹性好,能量损失较少,波经过反射之后反而对坡体产生了加固作用。与此同时,桩身剪力最大值一般位于坡体较易滑出位置与桩身相交处,桩两端点所受剪力与中间点的剪力反向；桩身弯矩一般在锚固段以下2m-3m左右处最大,呈对称分布。剪力与弯矩都是随着地震波作用先增大再减小最后增大达到最大值。 (7)对比分析了悬臂桩与全埋桩,桩锚固长度8m、10m和12m,桩间距5-10m时坡体动力变化情况,模型坡高30m(分三级放坡,每级10m)、坡比1：1时抗滑桩具有以下规律：①悬臂桩能改善坡体整体变形值,降低桩后动土压力值；全埋桩桩身内力较小,耗材少,降低工程造价；②抗滑桩锚固段长10m和12m要比长8m加固效果好；③桩间距9m和10m时坡体已经产生了大变形,说明边坡已发生破坏,这两种桩间距对边坡加固效果不好。
[Abstract]:Influenced by the "5.12" Wenchuan earthquake, a large number of slope geological disasters have occurred in the southwestern mountainous areas of China. In the process of highway construction in the strong earthquake area, the stability of the slope appears particularly important. In these different kinds of slopes, the slope of the fault zone has its own characteristics when the earthquake is unstable. The slope of the fault zone reinforced by pile is only a few inclined deformation under the earthquake action, most of the piles are basically unchanged, and the reinforced slope is relatively stable. Based on the above facts, this paper selects the slope of the Guangzhou Gansu highway fault zone as the research object, and uses the numerical simulation method to do no platform in the highway slope design. The dynamic response law of the slope with different slope and high slope, the reinforcement mechanism and the strengthening mode of the anti slide pile are studied. On this basis, the dynamic stability of the anti slide pile of the Guangzhou Gansu highway fault zone slope is analyzed. The main achievements obtained through the above study are as follows:
(1) the higher the slope of the fault zone, the higher the slope of the slope, the higher the horizontal displacement of the slope, the high increment of the horizontal displacement at the slope, the lower of the slope foot and the bottom of the slope; the maximum main stress is concentrated on the slope top and the slope. When the slope is up to a certain height, the slope surface forms the tensile stress zone which is connected with the slope, and the slope foot produces a more obvious stress concentration area. It is found that the higher the height of the slope of the fault zone is, the worse the self stability under the dynamic action. The horizontal displacement of the slope in different periods of earthquake action is recorded. It is found that the horizontal displacement value increases continuously under the continuous action of the seismic wave, and the cumulative deformation of the slope occurs.
(2) analysis of dynamic deformation of slope of fault zone: due to the loose and broken rock mass of the fault zone, during the propagation and action of the seismic wave in the rock and soil of the slope, the transverse waves and the longitudinal waves produced by the slope cause the interaction between the different parts of the rock and soil of the slope, and the tensile or shear deformation causes the failure of the slope and soil mass. At the same time, the seismic wave is propagating. Reflection and refraction will occur when the interface is encountered, and different seismic waves will superimpose synergistic effect, resulting in tensile deformation and shear deformation of rock and soil.
(3) using FLAC3D software to simulate the dynamic response characteristics of slope body before and after supporting, the anti slide pile can significantly improve the horizontal displacement of the slope top, restrain the deformation and damage of the rock slope, improve the distribution of the plastic zone of the slope top and the foot of the slope, make the distribution of the slope stress more uniform and ensure the stability of the slope.
(4) under the action of earthquake, the change of soil and internal force between piles is recorded. The pile tip is larger than the middle part of the pile, and it is prone to collapse. The pile shear force has been formed in the early stage of the earthquake action, and the earthquake action will only cause small changes in the shear force. The bending moment of the pile increases quickly to the maximum. The change of the bending moment of the pile body is first increased and then decreased from bottom to top. The maximum value is usually located near the middle position of the pile. When the anti slide pile is designed, the reinforcement should be added near the maximum internal force.
(5) the dynamic support effect of the anti slide pile is compared and analyzed. The displacement of the soil between the piles without sliding surface is gradually increased from the interior of the slope to the facing surface, the plastic deformation area of the slope is concentrated on the slope, the top of the slope is small and the internal force of the pile is small, and the displacement of the soil between the piles is increased from the interior of the slope to the air surface. A large number of plastic deformation zones exist at the top of the slope at the top of the slope. It is easy to move along the slip surface to the surface of the surface, and the internal force of the anti slide pile is large and easy to destroy. It is worth noting that the displacement of the soil between the piles can be significantly changed when the slope has a sliding surface, and the displacement is maximum in the sliding surface.
(6) the reinforcement mechanism of the anti slide pile to the slope of the fault zone in strong earthquake zone is summarized. The rock mass is loose and broken, and the vibration effect of the seismic wave is produced on the slope body, so that the rock mass is relaxed and then slips to the air surface during the repeated oscillation. When the anti slide pile is supported, it has the effect of compaction, the improvement of the pile surrounding rock mass, and the seismic wave. When the surface wave propagates from the slope body to the anti slide pile interface, a part of the wave propagates directly in the pile body, the other is propagated at the pressure arch between the pile and soil, and the seismic wave is propagated by the pressure arch to the anti slide pile. When the longitudinal wave and the shear wave propagate to the pile, the anti slide pile is better than the fault belt, and the energy loss is less and the wave passes through the reverse. At the same time, the maximum shear strength of the pile body is generally located at the intersection of the slope and the pile body. The shear strength of the two ends of the pile is opposite to the middle point. The bending moment of the pile body is the largest and symmetrical distribution at about 2m-3m below the anchorage section. The shear and bending moment are all along with the seismic waves. The effect increases first and then decreases and finally increases to the maximum.
(7) comparing and analyzing the dynamic changes of the slope body of the cantilever pile and all pile, pile anchor length 8m, 10m and 12M, the pile spacing of 5-10m, the model slope is 30m (three grade, each level), and the slope ratio 1:1 has the following rules: (1) the cantilever pile can improve the whole deformation value of the slope and reduce the value of the soil pressure after the pile; the internal force of the whole pile pile is small, The cost of the material is less and the cost of the project is reduced; (2) the length of 10m and 12m of the anchorage section of anti slide pile is better than that of the long 8m. 3. When the pile spacing is 9m and 10m, the slope has produced large deformation, which indicates that the slope has been damaged, and the two pile spacing is not good for the slope reinforcement.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U418.52

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