基于地层结构效应的变刚度抗滑桩与地层协同工作宏细观研究

Landslides hazard is encountered frequently，and its losses is serious. Anti-slide piles are widely used but its calculation method is not yet ripe, and landslides are becoming more complex and the governance requirements are becoming more elaborate. Today, anti-slide piles are arranged according to equal stiffness for uniform stratum or not, so that is not conducive to safety and economy of anti-slide pile. In the project, anti-slide piles of variable stiffness are used based on the stratum structure effect proposed by the applicant, the variable stiffness indicate the stiffness change of piles and pile rows caused by the difference of the reinforcement of pile in the vertical direction, pile spacing in the transverse direction, the pile row spacing in the longitudinal direction and pile cross-section size. And anti-slide piles of equal stiffness are taken as the special case of anti-slide piles of variable stiffness when the stratum structure is approximately uniform. The anti-slide piles and geological body should be taken as a whole, and the retaining ability of anti-slide stratum, such as the soil arch and sliding bed stratum, should be made of full use. The common anchor cable row of piles and a new anchor cable door double row of piles are chosen as research objects, The collecting of data of site test and monitoring, the indoor macroscopic and mesoscopic model experiment with digital mesoscopic cameras technology and image processing technology, three-dimensional granular flow numerical simulation of micromechanics and theoretical analysis are used, the macroscopic and mesoscopic mechanism of cooperation work between anti-slide piles and stratum and computation models are studied in the case of the stratum structures and the corresponding anti-slide piles of variable stiffness. Research can deepen and refine the analysis and computational theory of anti-slide pile, and possesses a guidance role in the slope treatment.

滑坡灾害严重。抗滑桩应用广泛但其计算方法还不成熟，且滑坡有向更复杂化而治理要求更精细化方向发展。目前对抗滑桩不论各地层均匀与否都采用均匀的等刚度布桩，这样不利于抗滑桩的安全性和经济性。本项目基于申请者提出的地层结构效应采用变刚度布置抗滑桩，变刚度包括桩身竖向上配筋、横向上桩距、纵向上排距及各桩截面大小等不同产生的桩身、桩排的刚度变化，且将地层结构近似均匀时的等刚度布桩作为变刚度布桩的特例考虑；将抗滑桩与地质体看成一个整体，充分利用土拱、滑床等抗滑地层的支挡能力。以普通的锚索排桩和新型的带锚索门式双排桩为研究对象，收集现场试验和监测资料，采用配有数字细观摄像和细观图像处理技术的室内宏细观模型试验、三维细观力学颗粒流数值仿真和理论分析，研究各地层结构及相应变刚度桩情形下抗滑桩与地层协同工作的宏细观机理及建立理论分析和计算模型。研究成果能深化和精细化抗滑桩分析和计算理论，对边坡治理具有指导作用。

在国家自然科学基金的资助下，本项目利用模型试验、三维数值模拟及理论分析方法，基于几种典型的地层结构，对边坡变刚度抗滑桩与地层协同工作进行了宏细观研究。主要取得了以下研究成果：1）得到了边坡变刚度抗滑桩布置的几种模式；2）建立了变刚度抗滑桩加固边坡的三维数值模型，在模型的左右两侧设置竖立的薄层岩壁，发现设置岩壁边界后，滑坡在横向上呈不均匀分布，与实际情况接近。3）研究了变刚度抗滑桩在桩横向变形、桩弯矩、桩的材料用量、边坡安全系数等方面的特性，并与等刚度抗滑桩进行了比较，显示了变刚度抗滑桩加固边坡的优越性；4）获得了不同深度处竖向上和水平上即三维土拱的发展、变化、自组织规律；发现相对桩后土拱，桩间土拱对于桩间距以及滑坡推力的变化响应更加敏感；土拱有明显的分层，靠近拱轴线处的土体中应力值较大，偏离拱轴线的土体中应力值较小，但是中轴线会随着滑坡力的增大逐渐向桩间移动。5）含锚门式抗滑桩的土拱情况随着深度的增加呈现处了先增大后减小的趋势，从土拱的质量以及数量上看，含锚门式抗滑桩的土拱均优于单排普通抗滑桩的土拱，土拱的形成更为规则，桩与土的协同工作效果更好。对变刚度含锚门式抗滑桩，从两侧到中间，边坡土体及桩的位移分布变得比较均匀，在受力上更为合理。且对本项目的情形，锚杆倾角30°时是最优布置。6）当滑坡推力大于桩后土拱承载力时，土拱并不立即破坏，而是将剩余的滑坡力传递到桩间，由桩间土拱提供抗滑力。对本项目的情形，边坡的悬臂式抗滑桩的间距为4倍桩宽度时，土拱能发挥最好支挡性能，边坡的安全性能够得到较好的保证；7）基于ABAQUS计算且考虑土拱的纵向传力系数，提出了桩后土拱和桩间土拱协同作用的桩间距计算模型，并对该计算模型条件下的桩间距计算公式进行了推导；8）给出了桩-土组合刚度的定义，分析了桩-土组合刚度的影响因素，对边坡剖面的应力及等效塑性应变等进行分析，解释了桩-土组合刚度的作用机理，最后基于综合刚度原理和双参数法挠度微分方程，分别给出了埋入式、悬臂式矩形抗滑桩的桩-土组合刚度的挠度微分方程，归纳和推导了各桩-土组合刚度条件下滑坡推力分布函数。9）基于离散元软件PFC3D，通过其内置的FISH语言编程建立了边坡变刚度抗滑桩的三维细观模型，分析了抗滑桩与地层协同工作细观机理、土拱效应以及变刚度抗滑桩的抗滑性状等。本项目对抗滑桩设计的安全性和经济效益有指导作用。