摘要
为研究不同初始破损程度、不同干湿循环次数及两者耦合工况对膨胀土孔洞及裂隙发育、演化规律的影响,以及相应的土体变形、力学行为,以合肥膨胀土为研究对象,对制备的不同初始破损程度(圆柱孔直径分别为0、2.5、5 mm)的3组20个试样进行干湿循环试验及三轴剪切试验(控制吸力为50 kPa,有效围压分别为100、200、400 kPa)。并解释了孔洞-裂隙的产生及发育新机制。结果表明:干湿循环次数为0时,一定程度的初始破损会提高土体的强度;与常规认识不同,干湿循环次数为1~2次时,初始破损的存在会诱导土体裂隙开裂的方向和贯通模式,形成的结构块较无破损土体形成的更完整,因而具有相对于无初始破损土体更高的强度;干湿循环次数为3次时,裂隙完全扩展,土体结构性被严重破坏,有无初始破损的土体强度趋于一致;孔洞-裂隙的演化机制是:脱湿-增湿过程中产生的水力梯度使土体具有不同的软硬性质和胀缩变形,产生的拉压应力在微裂纹、尖端形成应力集中而开裂,更易与具有的初始孔洞破损联合、交汇、贯通,萌生的裂隙增大了水汽交换界面面积,进一步平衡拉压应力而最终完全碎裂。研究可为普遍存在初始破损的膨胀土工程研究提供新的思路。
To study different degrees of initial damage, different drying-wetting cycles and the coupled effects on the development and evolution of pore and fissure of expansive soil, drying-wetting cycle tests and triaxial shear tests （suction is 50 kPa, net confining pressure is 100, 200, 400 kPa, respectively） are conducted on Hefei expansive soil specimens for 3 groups with different initial degrees of damage （the diameter of the cylindrical hole is 0, 2.5 and 5 mm, respectively）. If there is no drying-wetting cycle, a certain extent of initial damage can increase soil strength. If drying-wetting cycle is 1-2 times, the initial damage contributes to outcome of crack direction and penetration mode, forming intact block structure that has higher strength than that of the soil without initial damage. If drying-wetting cycle is 3 times, crack is able to expand completely and the strength of the soil with different degrees of initial damage becomes consistent with the soil without initial damage. The evolution mechanism of soil pore-fissure is that： the different strength and shrinkage deformation induced by hydraulic gradient when subjected to drying-wetting process will produce tension and compression stress in micro-crack tips and tear the tips up, which makes the tips combine with the initial hole damage, causing intersection and transfixion of the damage. Furthermore, the fracture is able to develop due to the increased water vapor exchange interface area in the fracture to further balance the compressive stress. The research provides a new insight for the study of expansive soil engineering with initial damage.
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2018年第2期571-579,共9页
Rock and Soil Mechanics
基金
国家自然科学基金项目资助(No.11572262)
中央高校基本科研业务费专项资金(No.XDJK2015C018
No.XDJK2016B006)~~
关键词
膨胀土
干湿循环
裂隙
破损
力学性能
expansive soil drying-wetting cycle fissure damage mechanical properties
