摘要
武汉天然老黏性土是一种超固结硬黏土,在开挖卸载条件下容易产生应变软化,经常给深基坑、边坡工程带来不利影响。目前对其超固结性、结构性以及剪切特性等还缺少深入认识。利用高压固结仪和三轴剪切仪对其饱和原状样和饱和重塑样分别进行了压缩试验和三轴不排水剪切试验,并且应用上下负荷面剑桥模型对原状样的三轴不排水剪切试验进行了模拟。研究结果表明:天然老黏性土为一种强超固结的结构性土,采用两种方法得到的原状土前期固结压力和结构强度基本一致;在低围压下,原状样明显表现出应变软化和剪胀性,其破裂面易受微裂纹影响;与文献中的天然软土不同,天然老黏性土在结构破坏后剪缩并不明显;原状样的黏聚力明显高于重塑样,两者内摩擦角非常接近;采用上下负荷面剑桥模型模拟的原状样应力-应变曲线和孔压曲线与室内试验结果基本一致。
The natural old clay in Wuhan is an overconsolidated stiff clay. It often shows strain-softening under the excavating and unloading condition,which might cause some adverse impacts on deep pits and slopes. However,its over-consolidation,structure and shear properties are not well recognized. In this paper,first,a set of highpressure oedometer tests and undrained triaxial tests were carried out on its saturated undisturbed and remoulded samples,respectively. Second,the undrained triaxial tests of undisturbed samples were numerically simulated with super-loading Cam-clay model. It was founded that the natural old clay could be classified as a strong overconsolidated clay,and the preconsolidation pressure and the structural strength obtained by two methods were consistent.Under low confining pressure,the undisturbed samples obviously present strain softening and shear dilatancy,and the failure patterns are often influenced by the micro fissures. After the structure collapses,the natural old clay presents little contraction,which is different from natural soft soils in the literature. The cohesion values of undisturbed samples are much higher than those of remoulded ones,and their internal frictional angles are very close.The stress-strain curves and pore pressure variation simulated by the super-loading Cam-clay model are generally in agreement with the experimental results.
出处
《水利与建筑工程学报》
2016年第1期78-84,共7页
Journal of Water Resources and Architectural Engineering
基金
博士后科学基金面上项目(2012M511669)
国家杰出青年基金项目(51025932)
国家自然科学基金(51308485)
关键词
天然硬黏土
三轴不排水剪切试验
前期固结压力
结构强度
natural stiff clay
undrained triaxial test
pre-consolidation pressure
structural strength
