摘要
青海季节性冻土地区工程建设受冻融循环作用和黄土湿陷性的双重影响,工程上常采用石灰与黄土拌和作为垫层材料以满足工程要求,但冻融循环作用依旧对地基土体的性能有所影响。为探究青海季节性地区气候变化对地基土所带来的不利影响,采用3种温控曲线(1#、2#和3#温控曲线)模拟了青海季节性冻土地区气候变化规律,通过无侧限抗压强度试验和SEM等微观试验,分析不同温控曲线对2∶8、3∶7灰土强度和微观结构的变化规律。结果表明3∶7和2∶8灰土的应力-应变关系均呈现应变软化型,0~6次冻融过程中试样的无侧限抗压强度随着冻融循环次数的增加逐渐降低,继续增加冻融循环次数后其强度有所上升;冻融循环6次时灰土内部孔隙分布相较于冻融20次时多,且随着冻融循环次数的增加颗粒间接触方式由点-点、点-面接触向面-面接触转变;1#温控曲线的微观定量参数较2#、3#温控曲线变化明显,经历1#曲线时试样内部孔隙更为圆滑,结构排列疏松,1#温控曲线对试样结构和强度的影响程度相对较弱。
In Qinghai,engineering construction is affected by the effects of freeze-thaw cycles and the properties of loess.Lime and loess are often mixed as cushion materials to meet engineering requirements,but the freezing and thawing effects still affect the performance of the foundation soil.To explore the adverse effects of climate changes in Qinghai’s seasonal regions on the foundation soil,three temperature control curves(1#,2#and 3#temperature control curves)are selected by using the frost heave circulation box to simulate the change law of temperature in Qinghai.Through the unconfined compressive strength(UCS)test and SEM,XRD microscopic test,to analyze the change trend of different temperature control curves on the strength and microstructure of lime-improved loess.The results show that the stress-strain relationship of lime-improved loess was strain-soften⁃ing.During the 0~6 freeze-thaw cycles,the UCS of the sample gradually decreased with the increase in the num⁃ber of freeze-thaw cycles,and its strength increased after the freeze-thaw cycles.The distribution of pores in the lime-improved loess at 6 freeze-thaw cycles was more than that at 20 times.And with the increase of the number of melting cycles,the contact mode between particles changed from point-to-point,point-to-surface contact to surface-to-surface contact.The micro-quantitative parameters of lime-improved loess changed more obviously when experiencing the temperature control curve of 1#than when experiencing the temperature control curves of 2#and 3#.The pores of the lime-improved loess were smoother and the structure arrangement was more disor⁃dered when going through the 1#temperature control curve.The 1#temperature control curve had relatively weak influence on the structure and strength of the lime-improved loess.
作者
解邦龙
张吾渝
孙翔龙
刘乐青
刘成奎
XIE Banglong;ZHANG Wuyu;SUN Xianglong;LIU Leqing;LIU Chengkui(College of Civil Engineering,Qinghai University,Xining 810016,China;Qinghai Key Laboratory of Building Energy Saving Materials and Engineering Safety,Xining 810016,China;Qinghai Provincial Key Laboratory of Plateau Green Building and Eco-community,Xining 810008,China;Qinghai Building and Materials Research Co.,Ltd.,Xining 810008,China)
出处
《冰川冻土》
CSCD
北大核心
2022年第1期262-274,共13页
Journal of Glaciology and Geocryology
基金
国家自然科学基金项目(52168054)
青海省科技计划项目(2020-ZJ-738)
青海省高原绿色建筑与生态社区重点实验室开放基金计划项目(KLKF-2021-007)资助。
关键词
冻融循环
石灰改良黄土
温控曲线
无侧限抗压强度试验
微观试验
freeze-thaw cycle
lime-improved loess
temperature control curve
unconfined compressive strength test
microscopic test
