斜打水泥土桩加固土质路堤的作用机理和稳定性评价研究

The inclined driven cement-soil pile is a kind of rapid strengthening measure applied in soil embankment, which has grown up in recent years. The theory studies obviously lag behind the actual engineering on its strengthening mechanism and the embankment stability after being strengthened. This project will make model tests for the soil embankment before and after being strengthened. After that, the large-scale direct shear tests will be made on the interface between soil and cement-soil with different roughness. Base on the direct shear test results, the mechanical properties and deformation rules for will be revealed for the interface between the inclined driven cement-soil pile and soil. And further, the corresponding constitutive model will be created for the interface. And this model will be developed into finite element software called ADINA, and the numerical model for the model tests will be structured, which will be verified and modified based on the model test results. The numerical model will be enlarged to full-scale size　in order to simulate the actual construction site. And by means of the numerical calculation and analysis, the laws　will be explored for the influence of pile row number , pile spacing, dip angle, pile length, and crossover length of the two flank piles to bearing capacity of the embankment, top settlement, lateral displacement of the side slope, stress distribution in the embankment and failure mode of the embankment. Along with the model test results, the action mechanism of the inclined driven cement-soil pile strengthening the soil embankment will be revealed.Based on the energy anaysis method, a kind of calculation method will be put forward for the safety factor of the strengthening embankment stability, by which, the embankmeng stability under different working conditions will be evaluated.The reasonable safety factor will be confirmed.At the same time ,along with the results of model tests and numerical simulation, the consolidation principle and the consolidation optimization method will be brought forward.

斜打水泥土桩是近几年兴起的土质路堤快速加固手段，其加固机理和加固路堤稳定性方面的理论研究明显滞后于工程实际。本项目以黄万铁路加固路堤工程为背景，开展斜打水泥土桩加固前后土质路堤的模型试验，并进行不同粗糙度水泥土面与土接触的大型直剪试验，揭示斜打水泥土桩-土接触面的力学特性和变形规律，建立接触面本构模型。将此接触面模型开发到有限元软件ADINA中，构建模型试验的数值模型，并基于试验成果对其验证和修正。将数值模型扩大至足尺模拟实际工点，并通过数值计算，探讨水泥土桩排数、桩间距、倾角、桩长、两侧桩体交叉长度对路堤承载力、顶面沉降、边坡侧向位移、路堤中应力分布和路堤破坏模式的影响规律，结合模型试验成果，揭示其加固土质路堤的作用机理。采用能量分析法提出斜打水泥土桩加固路堤稳定安全系数的计算方法，据此评价不同工况下路堤的稳定性，确定合理安全系数，并综合模型试验和数值模拟成果，提出加固的原则和优化方法。

斜打水泥土桩是近几年兴起的土质路堤快速加固手段，其加固机理和加固路堤稳定性方面的理论研究明显滞后于工程实际。本项目完成的工作和取得的成果如下：（1）开展了水泥土强度增长的直剪试验和无侧限抗压强度试验，获得了水泥土强度指标随水灰比和龄期的变化规律，建立了强度增长预测模型。（2）改进了ZJ-2型直剪仪，开展了斜打水泥土桩-土接触面试验，获得了水泥土-土接触面的力学和变形特性，建立了接触面本构模型。（3）构建了模型试验系统，开展了斜打水泥土桩加固土质路堤的模型试验，获得了不同加固情况对路基中应力分布和路基沉降的影响规律，初步揭示了斜打水泥土桩加固土质路堤的作用机理。（4）开展了斜打水泥土桩加固土质路堤的数值仿真，通过对路基中心断面不同高度处的应力和路基顶面沉降规律的综合分析和探讨，结合模型试验成果，揭示了斜打水泥土桩的作用机理：使加固排桩上方区域的应力向中间和两侧传递和扩散，可有效减小路基基床层的不均匀沉降；显著提高路基整体刚度和承载力；第一排桩的加固效果最为显著。（5）结合模型试验和现场实际，获得了斜打水泥土桩加固后路基稳定性的变化规律，并提出了斜打水泥土桩加固土质路堤稳定性的计算和综合评价方法，加固后的路基局部稳定性和整体稳定性可分别采用有限元强度折减数值分析法和等效瑞典条分法进行计算和评价，加固后的路基必须同时满足局部稳定性和整体稳定性的要求。研究成果可为斜打水泥土桩加固路堤工程设计和施工提供理论支撑和技术指导，同时，揭示了斜打水泥土桩的加固机理，在水泥土-土接触本构关系和稳定性计算等方面有所突破，具有积极的理论意义和科学价值。