季节性地下水变化作用红粘土路基沉降机理及时空演化规律

Red clay is easy to soften with water and crack without water. Settlement and deformation of red clay under seasonal dry-wet circulation and vehicle road will easily cause traffic accident. Therefore, research on the settlement and deformation of red clay under the influence of seasonal groundwater is imminent. In the research, red clay roadbed seepage situation under the seasonal dry-wet circulation will be studied, as well as soil strength attenuation and roadbed settlement and deformation. Through indoor dry-wet circulation test of undisturbed red clay and reshaped red clay, fracture evolution mechanism of red clay roadbed under the influence of seasonal groundwater will be revealed. Meanwhile, indoor roadbed model test and numerical simulation will be used to study roadbed seepage mechanism under the seasonal dry-wet circulation and explore temporal and spatial evolution laws of soil strength attenuation and roadbed settlement and deformation of red clay, thereby improve the seepage formula of unsaturated soil subgrade under the action of seasonal groundwater. thereby improve the seepage formula of unsaturated soil subgrade under the action of seasonal groundwater. Also, a load - groundwater ranged from - the roadbed 3-d finite element calculation model will be established to discover temporal and spatial evolution laws of red clay roadbed crack and settlement under the changes of seasonal groundwater. Besides, seasonal dry-wet circulation coupling mechanism under longer vehicle load will be investigated. Finally, control measures for red clay roadbed settlement will be discussed and proposed.

红粘土由于遇水容易软化，脱湿则容易开裂，车辆荷载作用下季节性干湿循环容易导致红粘土路基沉降变形引发交通事故。因此，研究季节性地下水作用下的红粘土路基沉降变形迫在眉睫。本课题研究红粘土路基季节性干湿循环情况下路基渗流情况，以及由此导致的路基土体强度衰减和路基沉降变形。通过原状红粘土和重塑红粘土干湿循环试验，揭示季节性地下水作用下的红粘土路基裂隙演化机理；通过室内路基模型试验和数值模拟计算，研究季节性干湿循环作用地下水渗流机理，探索红粘土土体强度衰减和路基沉降变形的时空规律，完善季节性地下水作用下非饱和土路基的渗流公式；建立荷载-地下水变幅-路基三维有限元计算模型，验证季节性地下水变化的红粘土路基裂隙和沉降的时空规律；研究长期车辆荷载作用下红粘土路基干湿循环耦合机理。本课题揭示地下水变化对红粘土路基沉降变形影响机理和时空演化规律，并提出红粘土路基沉降的控制措施。

红粘土作为一种收缩性明显的土体其产生的开裂破坏比一般粘土更明显，破坏性也更大，因此红粘土地区更应该注重由于水作用而导致的道路损坏问题。随着高速铁路的快速发展及高速公路的不断增加，因此迫切需要进行红粘土地区路基水作用沉降变形机理及控制措施研究，从而为路基的排水设计与地基处理提供理论依据及施工指导。.本项目的主要研究内容包括：（1）通过室内常规土工试验，确定红粘土土样各项基本物理性能和强度指标。研究红粘土的裂隙开展发育特性，阐明红粘土的裂隙发育随干湿循环次数的变化规律。根据理论分析，得出干湿循环过程中红粘土路基裂隙时空演化机理。（2）室内取土样进行三轴试验，通过干湿循环来模拟地下水位的变化，对不同干湿循环次数的红粘土进行应力应变分析，分析红粘土土体的抗剪强度变化，阐明地下水变化对红粘土路基土体的强度衰减规律。（3）自主设计室内实体路基模型，研发水位自动控制系统，进行室内模型试验，通过模拟观测模型试验的沉降量，建立地下水动态变化与红粘土路基沉降变化关系，理论分析红粘土地区地下水变化作用路基沉降变形机理，得出红粘土路基地下水变化作用沉降变形机理和强度衰减规律。