冻融条件下水泥煤渣改良土非均匀损伤特性

Non-uniform Damage Characteristics of Cement Cinder Improved Soil under Freeze-thaw Conditions

研究目的:为研究冻融循环作用下水泥煤渣改良土的非均匀损伤演化特性,利用冻融循环试验箱及CT扫描设备,开展单向冻融条件下水泥煤渣改良土的水分迁移试验及CT扫描试验。通过获得水泥煤渣改良土不同位置处的水分迁移量与冻融循环次数的关系,建立水泥煤渣改良土的水分迁移模型。考虑冻融过程中水泥煤渣改良土CT值非均匀分布及演化特性,建立水泥煤渣改良土的非均匀冻融损伤演化模型。研究结论:(1)单向冻融循环作用下,土体水分迁移大多发生在土样轴向方向上,呈现出顶部(冷端)大、底部(暖端)小的特点;(2)随冻融次数的增加,土中水分迁移能力逐渐增强,其中前5次冻融作用的影响较为明显;(3)冻融循环对土体细观结构造成了不可逆的损伤,随冻融次数的增加,CT值分布曲线整体向左移动,各截面CT值平均值均出现较明显的衰减;(4)基于CT值非均匀分布及演化特性所建立的损伤演化模型,能够较好地反映土样各截面结构的发展,可为寒区高速铁路工程建设提供参考和借鉴。

Research purposes:In order to study the non-uniform damage evolution characteristics of cement cinder improved soil under freeze-thaw cycle,the water migration test and CT scanning test of cement cinder improved soil under unidirectional freeze-thaw condition were carried out by using freeze-thaw cycle test chamber and CT scanning equipment.The relationship between water migration and freeze-thaw cycles at different locations of cement cinder improved soil was obtained,and a water migration model for cement cinder improved soil was established.Considering the non-uniform distribution and evolution characteristics of CT values in cement cinder improved soil during freeze-thaw process,a non-uniform freeze-thaw damage evolution model for cement cinder improved soil was established.Research conclusions:(1)Under the unidirectional freeze-thaw cycles,water migration mostly occurred in the axial direction of soil samples,showing the characteristics of large top(cold end)and small bottom(warm end).(2)With the increase of freeze-thaw cycles,the water migration capacity in soil gradually increases,and the influence of the first 5 freeze-thaw cycles was more obvious.(3)The freeze-thaw cycle causes irreversible damage to the soil meso-structure.With the increase of freeze-thaw cycles,the CT value distribution curve moves to the left as a whole,and the average CT value of each section decreases significantly.(4)The damage evolution model established based on the non-uniform distribution and evolution characteristics of CT values can better reflect the development of each section structures of soil samples.It can provide reference for the construction of high-speed railway projects in cold regions.