因冻土物理力学性质受环境影响变化极大，所以寒区工程大多采用“以桥带路”的形式，而目前活动层厚度随季节变化显著，桩基受冻融循环的间歇性蠕变病害问题日益凸显，究其原因为土石混合体-混凝土界面受冻融影响蠕变强度劣化所致。因此，本文为探究不同冻融循环次数下土石混合体-混凝土界面剪切蠕变特性开展了以下试验研究：（1）通过室内直剪试验，研究不同影响因素对土石混合体-混凝土界面的应力-位移曲线、抗剪强度以及其相关参数的变化规律，并基于冻融和含石率等参数，提出界面抗剪强度的经验公式；（2）基于直剪试验结果，开展不同工况下土石混合体-混凝土分级加载进行界面剪切蠕变试验，明确界面的蠕变特性、明晰界面蠕变强度，基于蠕变理论，以土石混合体-混凝土界面剪切蠕变试验为基础，在前人模型基础上并联加入塑性元件，考虑高加载系数下的界面松散化现象，建立土石混合体-混凝土界面黏弹塑性剪切蠕变模型，对试样结果进行参数辨识，验证并对比分析蠕变参数变化规律；（3）基于PFC2D软件构建界面蠕变模型，明晰剪切蠕变过程中裂隙发育、颗粒旋转、位移变化，从细观颗粒角度探究界面宏观蠕变变形破坏机制，为寒区桩基承载力劣化提供理论参考。

针对土石混合体-混凝土界面强度变化问题，研究表明应力-位移曲线在峰值后无软化现象，属于应变硬化性，界面的抗剪强度会随着冻融循环作用而出现明显的急剧下降、回升和稳态下降的趋势，抗剪强度随含石率呈现先增大后减小趋势；界面强度和黏聚力变化趋势基本一致，利用摩尔库伦理论模型，结合冻融次数和含石量等因素提出了一个用于评估土石混合体-混凝土界面抗剪强度的经验公式。

针对土石混合体-混凝土界面蠕变特性问题，发现剪切应力较小时，土石混合体-混凝土界面不具备明显的剪切蠕变特征，当施加各级荷载之后极短的一段时间内，剪切位移迅速增大，但剪切蠕变速率逐渐减小，呈现衰减特征。在此过程之后，蠕变剪切速率以及蠕变剪切位移均趋于0。当加载系数逐渐增大，剪切蠕变特征开始增强，并且剪切蠕变速率随着时间增加。大部分工况中加载系数达到0.85时，出现了较为明显的瞬时剪切蠕变、初始剪切蠕变、稳态剪切蠕变和非线性加速剪切蠕变阶段。冻融循环次数越多，破坏时所需蠕变剪切应力就越小，不同含石率下土石混合体-混凝土界面蠕变强度为常规直剪强度的57.71%~69.52%

针对土石混合体-混凝土界面剪切蠕变本构问题，考虑土石混合体-混凝土界面硬化及松散化效应，加入塑性构件改进Burgers模型建立土石混合体-混凝土界面剪切蠕变本构模型，对比分析不同工况下蠕变参数，结果发现粘滞系数与黏弹性模量G₂变化均为先增大后减小，粘滞系数在4、5级剪切荷载时呈增大趋势，松散化参数b在蠕变等级增加时也发生增大的现象说明界面松散化程度逐渐加重，法向应力的增大会急剧减小蠕变过程中界面松散性。

针对土石混合体-混凝土界面剪切蠕变过程中剪切带细观发展破坏特征，利用PFC模拟界面剪切蠕变过程，结果发现冻融循环次数与剪切破坏裂纹数量呈正相关，颗粒旋转及位移量受冻融作用影响较小；含石率的增加剪切带厚度随之变厚，总体看来不同含石率下界面的裂纹的生成方向均为剪切蠕变运动方向的反方向向剪切蠕变运动方向产生，裂缝宽度及空间分布受到界面含石率的影响。研究成果为土石混合体-混凝土界面蠕变体系的发展做出了重要贡献，并且为寒冷地区的桩基工程建设和维护提供了有价值的指导。

Due to the significant changes in environmental impact on frozen soil, most projects in cold regions adopt the form of "bridges leading roads". Currently, the thickness of the active layer varies significantly with the seasons, and the creep problem caused by freeze-thaw cycles is becoming increasingly prominent. Therefore, in order to explore the shear creep characteristics of the soil rock mixture concrete interface under different freeze-thaw cycles, the following experimental studies were carried out: (1) Through the indoor direct shear test, the stress displacement curve, shear strength and its related parameters of the soil rock mixture concrete interface affected by different factors were studied, and based on the freeze-thaw and rock content parameters, an empirical formula for the shear strength of the interface was proposed; (2) Based on the results of the direct shear test, the interface shear creep test of soil rock mixture concrete under different working conditions was carried out under graded loading to clarify the creep characteristics and creep strength of the interface. Based on the creep theory and the shear creep test of soil rock mixture concrete interface, plastic elements were added in parallel on the basis of previous models, and the interface looseness phenomenon under high loading coefficient was considered, Establish a viscoelastic plastic shear creep model for the interface between soil rock mixture and concrete, identify the parameters of the sample results, verify and compare the changes in creep parameters; (3) Based on PFC2D software, an interface creep model is constructed to clarify the development of cracks, particle rotation, and displacement changes during shear creep. The macroscopic creep deformation and failure mechanism of the interface is explored from the perspective of microscopic particles, providing theoretical reference for the deterioration of pile foundation bearing capacity in cold regions.

Research has shown that there is no softening phenomenon in the stress-strain curve after the peak value, which belongs to strain hardening. The shear strength of the interface will show a significant sharp decrease, rebound, and steady-state decrease trend with the freeze-thaw cycle, and the shear strength will first increase and then decrease with the stone content; The trend of changes in interface strength and cohesion is basically consistent. Using the Mohr Coulomb theory model and considering factors such as freeze-thaw cycles and stone content, an empirical formula for evaluating the shear strength of the soil concrete interface is proposed.

Regarding the creep characteristics of the interface between soil and rock mixture and concrete, it was found that when the shear stress is low, the interface between soil and rock mixture and concrete does not exhibit obvious shear creep characteristics. After applying various levels of loads, the shear displacement rapidly increases for a short period of time, but the shear creep rate gradually decreases, showing a attenuation characteristic. After this process, the creep shear rate and creep shear displacement both tend to zero. As the loading coefficient gradually increases, the shear creep characteristics begin to enhance, and the shear creep rate increases over time. When the loading coefficient reaches 0.85 in most working conditions, there are obvious stages of instantaneous shear creep, initial shear creep, steady-state shear creep, and nonlinear accelerated shear creep. The more freeze-thaw cycles, the smaller the required creep shear stress for failure. When the loading coefficient is high, the number of freeze-thaw cycles has a greater impact on the shear creep curve. The shear strain at the inflection point increases with the increase of the loading coefficient.

In response to the constitutive problem of shear creep at the interface between soil and rock mixture and concrete, considering the hardening and loosening effects of the interface between soil and rock mixture and concrete, a plastic component was added to improve the Burgers model and establish a shear creep constitutive model for the interface between soil and rock mixture and concrete. A comparative analysis of creep parameters under different working conditions was conducted, and it was found that the changes in viscosity coefficient  and viscoelastic modulus G₂ first increased and then decreased, The viscosity coefficient  shows an increasing trend at shear loads of levels 4 and 5, and the hardening parameter a also increases with the increase of the load coefficient. However, the load has significantly exceeded the long-term strength, and the interface still accelerates creep failure. The phenomenon of the loosening parameter b also increases when the creep level increases indicates that the degree of interface loosening gradually increases, and the increase of normal stress will sharply reduce the interface looseness during the creep process.

In response to the microscopic development and failure characteristics of shear bands during the shear creep process of the soil rock mixture concrete interface, PFC was used to simulate the interface shear creep process. The results showed that the number of freeze-thaw cycles was positively correlated with the number of shear failure cracks, and the particle rotation and displacement were less affected by freeze-thaw effects; As the stone content increases, the thickness of the shear band becomes thicker. Overall, the direction of crack generation at the interface under different stone content is the opposite direction of shear creep movement, and the width and spatial distribution of cracks are affected by the stone content at the interface.This research achievement has made an important contribution to the development of the creep system at the interface between soil rock mixture and concrete, and provides valuable guidance for the construction and maintenance of pile foundation engineering in cold regions.

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