【作者】 朱登元；

【导师】 姚占勇；

【作者基本信息】 山东大学 ， 岩土工程， 2014， 博士

【摘要】 路基宽度不足是被交路升级改建中立体交叉路段的关键制约因素之一。由于环境条件和建设成本等原因,柱式桥台被大量应用在立体交叉路段的立交桥中,在被交路提升等级改建时,利用上跨公路柱式桥台能够为被交路提供通行空间的潜力,在不拆除重建、不中断交通、不影响通行安全的前提下,挖除台前填土,增设挡墙成为最经济途径。但在施工及运营过程中,不能回避的问题是,由于台前填土、锥坡的挖除和挡墙基坑的开挖,桥台填土外露面垂直,坡度大、边坡高,在路基与路面结构自重、行车荷载、桥头跳车的作用下,失稳破坏造成安全事故的危险较高。针对特殊的工程条件和施工要求,开展室内模型试验,在研究袖阀管劈裂注浆加固路基荷载响应特性,探察微桩与劈裂土体的浆液在土中形成层状骨架结构的基础上,利用解析和有限元数值计算的方法对土中骨架结构的轮载静、动力特性以及加固参数、边坡稳定性进行扩展分析；以工程实例为背景,开展边坡填土分段分级顺序挖除、台前台后注浆加固的数值模拟和分析,并经现场验证；采用数值计算和现场检测相结合的方法研究锚拉式挡墙墙后土压力、墙体应力与位移、锚杆轴力在施工和运营过程中的分布及演变规律。提出了对台背填土及台前地基土进行袖阀管劈裂注浆加固,分段分级挖除填土并采用锚拉式钢筋混凝土挡土墙进行支护的柱式桥台改建方法。本课题取得了如下创新性研究成果：(1)通过室内路基模型的毛细水上升试验、分级循环加载试验、袖阀管劈裂注浆加固试验,研究其在4级荷载作用下稳定性衰减的原因和规律,微桩及浆液在土中的形态和分布。结果表明：粉土具有强烈的毛细水作用,导致路基土体含水率增大,潜水位以上60cm为近饱和状态,饱和区含水率达27.5%,毛细水作用区比新建路基时的含水率平均高出7.2%,土体的抗剪强度下降,路基的总体刚度降低70%,超载作用下路基顶面竖向塑性累积变形随着荷载的增大而快速增加,呈破坏趋势；衰减路基模型的竖向应力分量减小而水平应力分量增大,应力分量的变化反应了路基模型边坡有侧滑破坏的趋势；袖阀管劈裂注浆加固路基模型中土体的竖向应力及水平应力都显著减小,浆液劈裂土体水平成层,并不与被加固粉土路基土体渗透掺混,成层的凝固浆液不仅阻断了土中毛细水上升的通道,而且与微桩形成土中骨架结构,这种土中骨架结构可使衰减路基的总体刚度提高到新建路基的116%。(2)土中骨架结构的劈裂层及微桩采用混凝土损伤塑性模型、土体采用Mohr-Coulomb模型,通过分离建模嵌入技术模拟劈裂层的加固作用,实现对刚度相差较大的土中骨架结构轮载响应的弹塑性数值分析；土中骨架把荷载分散传递到土体的深部,路面与土体的整体刚度增大,弯沉变形减小；顶部桩间土体竖向应力在加固前、后相差大约50%,加固深度应大于轮载产生的附加应力的影响范围,大约10m。土中骨架结构轮载动力分析时位移值变小,基层层底拉应力降低,但波动影响范围增大,土基以上各路面结构层在移动荷载下的竖向位移时程曲线一致,其中沥青面层位移值最大为0.16mm,小于静力下的0.26mm；位移峰值延后应力峰值0.005s,土中骨架结构荷载响应快。加固参数的分析表明,劈裂层间距越大,顶面弯沉值就越大,从1.0m至2.0m的变化对弯沉值的影响较大,劈裂层间距应控制在1.0m以内。土中骨架结构加固边坡的稳定性分析表明,边坡点的水平位移在强度折减系数3.80时突变(数值计算收敛),而加固前为1.85(数值计算不收敛),边坡的稳定安全系数提高了一倍多。(3)数值模拟台前填土不同挖除顺序的施工过程,分析开挖土体的稳定性和成拱效应,得到一定高度下跳槽开挖最大宽度为12m；以极限破坏状态时对应的PEMAG塑性区域分布和滑裂面的位置为参考确定施工加固区域。现场验证了柱式桥台前坡挡墙化改造方法,台后主动土压力区和台前被动土压力区的注浆加固,有效提高了加固区土体的抗剪强度和抗变形能力,挖除施工过程中无坍塌、掉落、滑移等现象,施工中上跨高速公路通行正常。(4)锚拉式挡墙在施工过程中的静力、桥头跳车冲击动力的数值模拟及现场锚杆拉拔、墙体位移、锚杆拉力监测和工后检测分析表明：墙后土压力沿墙高自上而下逐渐增大,但土压力的分布受锚杆影响,下层锚杆影响区土压力最大,上层次之,中层最小；墙后土压力沿墙宽从中到边逐渐减小,挖除对墙后土压力分布影响较大；注浆加固后墙后土体的侧压力系数降低。相邻节段挖除过程中,墙顶水平位移不断增大,从第1级至第4级墙顶水平位移增大了0.66mm,与检测结果(0.65mm)相符。锚杆轴力在墙高方向底层最大,中层次之,顶层最小；在墙宽方向,锚杆轴力分布不均,墙中最小,墙1/4处最大。锚拉式挡墙在施工过程中柔性变形,墙后土压力的分布复杂,不能按静止土压力理论计算。锚杆在试验拉拔力范围内与锚固土体粘结良好,拉拔力与伸长值呈线性相关,处于弹性范围内。试验锚杆在施工期处应力松驰阶段,锚杆拉力没有突然变化,说明墙后土体整体稳定；墙顶位移随时间逐渐增大,而后趋于平缓,位移增长期主要是施工期,最大位移为lmm。运营过程中各锚杆呈应力松驰状态而后趋于稳定,不同位置的锚杆拉力降低幅值也不一样,拉力降低最多的是行车道挡墙的下层锚杆,其次为上层锚杆,而内侧超车道挡墙锚杆拉力降低幅值基本一致,这说明行车道的墙后土体有向侧前方滑移变形的趋势,而超车道墙后土体侧向变形小。工后检测表明,墙土结构稳定。最后,对后续研究工作的方向进行了简单的讨论。更多还原

【Abstract】 With the development of the economy and society, the capacity of many highway is no longer meet the needs of development because of the increasing volume of traffic and the relative scarcity of land resources, it shall be in the construction peak for road grade to be upgraded in current and future of a certain period. The lack of subgrade width is one of the key constrained factors in upgrading and improvement at the interchange section. Buried abutment is designed generally and widely used in the overpass because of construction costs and environmental conditions. The buried abutment slope can be transformed as potential space to provide clearance for the interchange section. Without bridge demolition and reconstruction, and not interrupting the traffic, slope soil excavation and anchored retaining wall by tie rods construction are the most economical way. But during construction and operation, the risk of accidents caused by soil instability and failure will be high, because the soil excavation outer face of the conical slope, abutment slope and foundation pit of retaining wall is vertical, high, and dangerous, especially under the weight load of embankment and pavement structure, traffic, and bridgehead vibration.Because of the special conditions for the engineering and construction requirements, a series of studies was carried out relying on the G1511highway interchange reconstruction project at Linyi section. First, a large-scale indoor model test was carried out in the study of the attenuation law of strength and stiffness for silt embankment with the action of capillary water, and the reinforcement effect of the embankment by the Soletanche method. Then, based on the model test observation of concrete skeleton in soil formed from micro-piles and fracture grouting layers, analytical and finite element methods are used for concrete skeleton in soil to solve stress, strain and displacement with static loads and dynamic loads of vehicle. The reinforcement parameters and slope stability analysis are also studied with Abaqus6.10. Third, with an engineering example as the background and certificated on-site, the slope soil excavation order in section horizontally and in layer vertically, soil reinforcement by the Soletanche method to active pressure soil and passive pressure soil of the abutment are simulated by numerical method. Finally, the distribution and the variation of lateral earth pressure, stress and displacement of the retaining wall and axial force of the bolt are studied by numerical method and site detections during construction and operation. In brief, an internal and external dual reinforcement program is proposed to the soil excavation, the internal program is soil reinforcement by the Soletanche method to active pressure soil and passive pressure soil of the abutment, the external program is anchored retaining wall by tie rods to the soil after slope excavation in section horizontally and in layer vertically.The main achievements of this thesis are as follows:1. The attenuation reason and law of strength, stiffness and stability for silt embankment with the action of capillary water, the morphology and distribution of micro-pile and grouting, are studied by soil indoor model of capillary water rise test of subgrade, grading cyclic loading test, and the Soletanche method reinforcement test at load level4. The results indicate that:the capillary water in the silt soil is serious and makes the soil moisture of subgrade increasing near to saturation at60cm above dive water level, the moisture of saturated district can up to27.5%, and higher7.2%compare to the original subgrade model. The general stiffness of the silt embankment will reduce70%because of the capillary water, and the shear strength of embankment soil will decline, the vertical plastic deformation of the embankment increases rapidly with the increasing load. The vertical soil stress component of the attenuation subgrade model reduces but horizontal stress component increases, this changes of stress component indicates the sideslip damage trend of the model. The vertical and horizontal stress are significantly reduces in the Soletanche method reinforcement model, the horizontal layered fracture grouting not only blocks the rising channels of capillary water, but also forms concrete skeleton with the bottom expansion micro-piles to bear the load together, of about50%. This concrete skeleton can promote the overall stiffness in soil reinforcement subgrade to116%, compared to the original subgrade model.2. The elastic and plastic mechanical properties of concrete skeleton in soil under wheel loads were calculated from static to dynamic analysis. The micro-pile and split crack layer of the concrete skeleton in soil used concrete damage plastic model, the soil used Mohr-Coulomb model, and the layered grouting reinforcement role was simulated by embedded technology of Abaqus6.10. The static analysis results indicate that:the load is transferred to the depth of the soil by the concrete skeleton, the general stiffness of the pavement and subgrade enlarged and the deflection reduced. The vertical soil stress in top reinforced department among micro-piles is less about50%than before. The depth of reinforcement soil is about10m and should be greater than the attached stress effects range produced by wheel loads. The dynamic analysis results indicate that: the displacement of the concrete skeleton in soil and the base layer tension stress of pavement structure reduce, but the fluctuations effects range enlarges. The vertical displacement time-history curve of every pavement layers is consistent, which the top asphalt concrete surface layer maximum for0.16mm, small than0.26mm of static. The displacement peak delayed the stress peak0.005s, so the concrete skeleton in soil response to load faster than before. The analysis of reinforcement parameter indicates that the distance among grouting layers larger, the deflection greater, especially varies from1.0m to2.0m, so the distance should be controlled less than1.0m. The reinforcement soil slope stability analysis of concrete skeleton indicates that the horizontal displacement of the key slope point suddenly increases when the strength reduction factor is3.80(numerical convergence), while it is1.85before the reinforcement (numerical computation does not converge), safety factor of slope stability is2-time more than before.3. The different soil excavation sequence of the slope is simulated to analysis the stability and arching effect during construction program, the maximum12m width of the excavation is determined under a certain height. The reinforcement construction area is determined as a reference according to the PEMAG distribution at critical damage state and slip surface position. The soil reinforcement by the Soletanche method to active pressure soil and passive pressure soil of the abutment improves the shear strength and the resistance to deformation, there is no collapse, fall, and slip at the site construction. The relevant results provide reliable technical references to similar project for design and construction.4. The numerical simulation of the anchored retaining wall by tie-rods in slope transformation under static and dynamic load, the anchor rod pulled out detection test in site, the displacement of the retaining wall and anchor rod force monitoring, and post-construction inspection show that:The lateral earth pressure gradually increases from up to down in the height direction of the wall, but the distribution of the pressure is up to the anchor rod, lower anchor rod effects district soil pressure maximum, upper followed, the middle minimum. The lateral earth pressure along wall width direction reduces gradually from side to center, slope excavation at adjacent section influence the pressure distribution. The lateral earth pressure coefficient reduces after soil reinforcement by grouting. The horizontal displacement at top of the retaining wall increases during the adjacent slope section excavation from the1th to4th level, the horizontal displacement increases0.66mm and matches the test results (0.65mm).The bolt axial force is not the same in height direction along the retaining wall; the bottom bolt is maximum, then the middle, and top minimal. The bolt axial force is neither the same in width direction, the minimum axial force at the center bolt of the wall, the maximum axial force at the one-fourth. The deformation of the anchored retaining wall by tie-rods is flexible during the construction, and the lateral earth pressure distribution is complex, it cannot be calculated by at-rest earth pressure theory. The bolt bonds with soil well at the bolt pulling force test range, pulling force and elongation values linearly correlated in the elastic range. There are no suddenly tension stress changes to the test bolt during the construction; the bolt is at the stress relaxation stage, which indicates the stability of the wall and soil in general. The displacement at the top of the retaining wall increases gradually with time, mainly increases at the construction period, and then increases slowly, and the maximum displacement is1mm.The anchor bolts are at the stress relaxation stage, and then tend to stable at the process. The reducing amplitude of bolt tension force differs with the location in the retaining wall; the most one is the lower anchor rod at carriage way, then the upper anchor rod, but the bolt tension force reducing amplitude is about the same at overtaking lane, which means the front sideslip deformation trend of the soil behind the wall at carriage way, and the soil deformation is small at overtaking lane. Post-construction inspection proves the stability of the retaining wall and the soil.Finally, the further research works have been briefly discussed.更多还原