| 冻融状态和初始含水率对土壤力学性能的影响 |
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| 引用本文： | 张惠忍,李法虎,吕威.冻融状态和初始含水率对土壤力学性能的影响[J].农业工程学报,2017,33(3):128-133. |
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| 作者姓名： | 张惠忍 李法虎 吕威 |
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| 作者单位： | 1. 中国农业大学水利与土木工程学院,北京,100083;北京市城市河湖管理处,北京,100089;2. 中国农业大学水利与土木工程学院,北京,100083 |
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| 基金项目： | 国家自然科学基金重点项目（41230746） |
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| 摘 要： | 冻融状态影响土壤的抗剪强度从而威胁季节性冻土地区的工程安全、边坡稳定以及土壤流失。通过直剪试验测定了不同冻融状态和初始含水率对青藏地区(S1)和北京地区(S2)土体抗剪强度的影响。结果显示,2种土在未冻和已融状态下的抗剪强度相似,且均随着土含水率的增加而减小,但S1土抗剪强度比S2土大7.5%~9.7%;在冻融状态下,S1土抗剪强度随着土含水率的增加而增大,而S2土则随之减小。S1冻融土抗剪强度在低含水率(≤13.5%)时小于未冻土和已融土,而在高含水率(≥24.5%)时则反之;S2冻融土抗剪强度小于未冻土和已融土。在冻融状态下2种测试土的内摩擦角显著小于未冻土和已融土,而黏聚力整体上则大于未冻土和已融土。与未冻土或已融土相比,2种土在冻融状态下的强度相对较低,宜作为季节性冻土地区工程设计以及土壤流失防治的基本状态。
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| 关 键 词： | 土壤 土壤含水率 抗剪强度 冻融状态 青藏高原 土壤内摩擦角 土壤黏聚力 |
| 收稿时间： | 2016/5/12 0:00:00 |
| 修稿时间： | 2016/12/19 0:00:00 |
Effects of freeze-thaw status and initial water content on soil mechanical properties |
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| Zhang Huiren,Li Fahu,Lü Wei.Effects of freeze-thaw status and initial water content on soil mechanical properties[J].Transactions of the Chinese Society of Agricultural Engineering,2017,33(3):128-133. |
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| Authors: | Zhang Huiren Li Fahu Lü Wei |
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| Institution: | 1. College of Water Resources and Civil Engineering, China Agriculture University, Beijing 100083, China; 2. Beijing Municipal River and Lake Management Office, Beijing 100089, China;,1. College of Water Resources and Civil Engineering, China Agriculture University, Beijing 100083, China; and 1. College of Water Resources and Civil Engineering, China Agriculture University, Beijing 100083, China; |
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| Abstract: | The freeze-thaw conditions affect soil shear strength and hence threaten engineering safety,soil slope stability,and soil loss in seasonal frozen-soil region.Shear strength was tested for 2 kinds of soils (sandy loam in Qinghai-Tibet Plateau (S1) and silt loam in Beijing region (S2)) under 3 freeze-thaw statuses (unfrozen soil,frozen soil,and thawing soil after frozen) and different initial water contents (8.0％-31.0％ in mass fraction) by direct shear apparatus in the laboratory.The unfrozen soil specimen did not suffer freeze-thaw processing in the laboratory,the thawing soil specimen was sheared after frozen at-18℃ for 24 h,and the thawed soil specimen was done after frozen at-18℃ for 24 h and then thawed at 27℃ for 12 h.The shear velocity was set to 2.4 mm/min.Experimental results showed that the shear strength of the 2 types of soils increased approximately linearly with the increasing of normal stress,and the shear strength envelope of unsaturated thawing soil could be expressed by total stress Mohr-Coulomb failure criteria under tested normal stress,freeze-thaw status and soil water content conditions.The shear strengths of unfrozen and thawed soils were similar to each other and their difference was averagely 3.4％-3.7％ after one freeze-thaw cycle,and they decreased with the increased initial soil water content for the 2 types of soils.The shear strength of soil sample S 1 was 7.5％-9.7％ greater than that of S2 under the unfrozen and thawed statuses.Under the thawing status,the shear strength of S 1 increased with the initial soil water content but that of S2 decreased with it.The shear strength of the thawing S 1 soil was smaller than that for the unfrozen and thawed soils at low soil water content (13.5％) but it was on the contrary when the water content was higher;the shear strength of the thawing S2 soil was smaller than that for the unfrozen and thawed soils under all the soil water contents.Under the unfrozen,thawed,and thawing statuses,the internal friction angle for both types of soils declined with the increase of soil water content.The internal friction angles under the unfrozen and thawed statues were similar to each other but they were significantly greater than that under the thawing status.The soil cohesion under the unfrozen or thawed statuses decreased with the increased soil water content and that under the thawed status was smaller than that under the unfrozen status for both types of soils.Under the thawing status,the soil cohesion of S 1 increased significantly with the increased initial soil water content but that of S2 first increased and then decreased with it.The soil cohesion of both types of soils under the thawing status generally was significantly greater than that under the unfrozen and thawed statuses.The variation ranges of the internal friction angle for the 2 types of soils were similar to each other but their soil cohesion was significantly different under experimental conditions.The soil at the thawing status had a relatively low shear strength compared with that at the unfrozen or thawed statuses,and hence the thawing status should be adopted as the basic status for engineering design or soil loss prevention in seasonal frozen-soil regions. |
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| Keywords: | soils soil moisture shear strength freeze-thaw status Qinghai-Tibet Plateau soil internal friction angle soil cohesion |
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