Study on shear strength anisotropy of undisturbed loess-paleosol sequence in Jingyang county#br#
ZHANG Qiying1，2，XU Panpan1，2，QIAN Hui1，2
(1. School of Environmental Science and Engineering，Chang?an University，Xi?an，Shaanxi 710054，China；2. Key Laboratory of Subsurface Hydrology and Ecology in Arid Areas，Ministry of Education，Chang?an University，Xi?an，Shaanxi 710054，China)
Abstract：System sampling was conducted with an interval of 1 meter at Xiushidu section of Jingyang south plateau，Guanzhong Basin，Shaanxi. Direct shear test was executed under different or same vertical pressures，and microstructure and basis physical properties including dry density，moisture content and porosity were tested. The anisotropic characteristics of the shear strength of undisturbed loess were studied，and their formation mechanisms and influencing factors were also analyzed. The results show that the structural parameters of loess present different anisotropy characteristics as well as the shear strength. The vertical shear strength is generally greater than the horizontal shear strength for the layers above L7，while the ratio of the vertical shear strength to the horizontal shear strength for L7 and below layers is less than 1. The anisotropy degree of paleosol is larger than that of corresponding loess. The main influencing factors on shear strength anisotropy of loess-paleosol sequence are the porosity and the moisture content. The effect of the porosity on the horizontal shear strength is greater than that on the vertical shear strength，while the water content is opposite. The dry density is directly proportional to the shear strength but has little effect on the anisotropy of the shear strength. The shear strength anisotropy of natural loess is due to different arrangements of soil particles by aeolian deposition and rotation and rearrangement of particles during shearing.
[1] LI X A，LI L C. Quantification of the pore structures of Malan loess and the effects on loess permeability and environmental significance，Shaanxi Province，China：an experimental study[J]. Environmental Earth Science，2017，76(15)：14.
[2] CHANG J M，SONG S W，FENG H P. Analysis of loess slope stability considering cracking and shear failures[J]. Journal of Failure Analysisand Prevention，2016，16(6)：982–989.
[3] 张 涛. 基于三轴压缩试验的山西原状马兰(Q3)黄土抗剪强度各向异性的研究[硕士学位论文][D]. 太原：太原理工大学，2018.(ZHANG Tao. Study on shear strength anisotropy of undisturbed Malan(Q3) loess in Shanxi based on triaxial compression test[M. S. Thesis][D]. Taiyuan：Taiyuan University of Technology，2018.(in Chinese))
[4] LI D J，ZHAO J T，PANG C Y，et al. Stability analysis of loess slope with hidden hole by numerical methods[J]. Applied Mechanics and Materials，2012，170–173：306–311.
[5] 王 烁. 泾阳南塬黄土的力学特性与滑坡机制研究[硕士学位论文][D]. 西安：长安大学，2018.(WANG Shuo. Study on Mechanical Properties and Landslide Mechanism in the South of Jingyang[M. S. Thesis][D]. Xi?an：Chang?an University，2018.(in Chinese))
[6] ZHUANG J Q，PENG J B. A coupled slope cutting—a prolonged rainfall-induced loess landslide：a 17 October 2011 case study[J]. Bulletin of Engineering Geology and the Environment，2014，73(4)：997–1 011.
[7] LI Y R. A review of shear and tensile strengths of the Malan Loess in China[J]. Engineering Geology，2017，236：4–10.
[8] HU C M，WANG X Y，MEI Y，et al. Compaction techniques and construction parameters of loess as filling material[J]. Geomechanics and Engineering，2018，15(6)：1 143–1 151.
[9] LIPIEC J，CZYZ E A，DEXTER A R，et al. Effects of soil deformation on clay dispersion in loess soil[J]. Soil and Tillage Research，2018，184：203–206.
[10] 安亚芳，梁庆国，赵 磊，等. 兰州Q4黄土力学性质的各向异性初探[J]. 兰州交通大学学报，2011，30(1)：90–96.(AN Yafang，LIANG Qingguo，ZHAO Lei，et al. Preliminary study on the anisotropy of mechanical properties of Lanzhou Q4 loess[J]. Journal of Lanzhou Jiaotong University，2011，30(1)：90–96.(in Chinese))
[11] ZHA X X，DASSEKPO J B M. Compression and characterization of alkali-activated loess[C]// IOP Conference Series: Materials Science and Engineering. [S. l.]：[s. n.]，2018， 431：092012–092018.
[12] LI Y R，ZHANG T，ZHANG Y B，et al. Geometrical appearance and spatial arrangement of structural blocks of the Malan loess in NW China：implications for the formation of loess columns[J]. Journal of Asian Earth Sciences，2018，158：18–28.
[13] LIANG Q G，LI J，WU X Y，et al. Anisotropy of Q2 loess in the Baijiapo Tunnel on the Lanyu Railway，China[J]. Bulletin of Engineering Geology and the Environment，2016，75(1)：109–124.
[14] 衣浩源. 原状马兰黄土抗剪强度的各向异性[硕士学位论文][D]. 太原：太原理工大学，2017.(YI Haoyuan. Anisotropy of shear strength of undisturbed Malan loess[M. S. Thesis][D]. Taiyuan：Taiyuan University of Technology，2017.(in Chinese))
[15] 吴旭阳，梁庆国，牛富俊，等. 宝兰客运专线王家沟隧道原状黄土各向异性研究[J]. 岩土力学，2016，37(8)：2 373–2 382.(WU Xuyang，LIANG Qingguo，NIU Fujun，et al. Anisotropy of undisturbed loess in wangjiagou tunnel of baolan passenger dedicated line[J]. Rock and Soil Mechanics，2016，37(8)：2 373–2 382.(in Chinese))
[16] LI T L，WANG C Y，LI P. Loess deposit and loess landslides on the chinese loess plateau[J]. Progress of Geo-Disaster Mitigation Technology in Asia，2013，9：235–261.
[17] LUO Y，WANG T H，LIU X J，et al. Laboratory study on shear strength of loess joint[J]. Arabian Journal for Science and Engineering，2014，39(11)：7 549–7 554.
[18] 温晓坤. 泾河南岸Q2古土壤控滑机制研究[硕士学位论文][D]. 西安：长安大学，2017.(WEN Xiaokun. Study on the sliding mechanism of Q2 Paleosol at the South Bank of Jing River[M. S. Thesis][D]. Xi?an：Chang?an University，2017.(in Chinese))
[19] 洪 勇，车效文，郑孝玉，等. 陕西泾阳南塬滑坡干湿黄土快速大剪切力学特性[J]. 吉林大学学报：地球科学版，2017，47(4)：1 207– 1 218.(HONG Yong，CHE Xiaowen，ZHENG Xiaoyu，et al. Fast shear behavior of saturated and dry loess at South Plateau Landslide of Jingyang，Shaanxi[J]. Journal of Jilin University：Earth Science，2017，47(4)：1 207–1 218.(in Chinese))
[20] 马鹏辉，彭建兵，李同录，等. 陕西泾阳“3•8”蒋刘黄土滑坡成因及运动特征分析[J]. 工程地质学报，2018，26(3)：663–672.(MA Penghui，PENG Jianbing，LI Tonglu，et al. Forming mechanism and motion characteristics of the“3•8”Jiangliu loess landslide in Jingyang County of Shaanxi Province[J]. Journal of Engineering Geology，2018，26(3)：663–672.(in Chinese))
[21] 许 强，魏 勇，彭大雷，等. 泾阳南塬蒋刘4#滑坡特征及成因机制[J]. 水文地质工程地质，2018，45(1)：123–130.(XU Qiang，WEI Yong，PENG Dalei，et al. Characteristics and failure mechanism of the Jiangliu 4# landslide in the southern tableland in Jingyang County[J]. Hydrogeology and Engineering Geology，2018，45(1)：123–130.(in Chinese))
[22] 葛瑞华. 泾阳南塬灌溉诱发型黃上滑坡形成机制试验研究[硕士学位论文][D]. 西安：西北大学，2016.(GE Ruihua. The experimental study on the formation mechanism of irrigation-induced loess landslide at sout jingyang plateau[M. S. Thesis][D]. Xi?an：Northwest University，2016.(in Chinese))
[23] 董金庆. 泾阳南塬庙店黄土滑坡启动机制及运动特征研究[硕士学位论文][D]. 西安：长安大学，2017.(DONG Jinqing. Study on the trigger mechanism and motion characteristics of loess landslide of Jingyang Village at South Jingyang Plateau[M. S. Thesis][D]. Xi?an：Chang?an University，2017.(in Chinese))
[24] 郭泽泽，李喜安，陈 阳，等. 基于SEM-EDS 的湿陷性黄土黏土矿物定量分析[J]. 工程地质学报，2016，24(5)：899–906.(GUO Zeze，LI Xi?an，CHEN Yang，et al. Analysis of clay minerals in collapsible loess with SEM-EDS[J]. Journal of Engineering Geology，2016，24(5)：899–906.(in Chinese))
[25] 林 涛. 泾阳修石渡剖面黄土微观结构研究[硕士学位论文][D]. 西安：长安大学，2018.(LIN Tao. Study on microstructure of loess in Xiushidu Section of Jingyang County[M. S. Thesis][D]. Xi?an：Chang?an University，2018.(in Chinese))
[26] 张晓周，卢 婷，卢玉东，等. 扫描电镜下泾阳南塬马兰黄土的孔隙特征[J]. 水土保持通报，2018，38(3)：212–216.(ZHANG Xiaozhou，LU Ting，LU Yudong，et al. Pore characteristics of Malan loess under scanning electron microscopy in South Jingyang Plateau[J]. Soil and Water Conservation Bulletin，2018，38(3)：212–216.(in Chinese))
[27] 王慧妮，倪万魁. 基于计算机X射线断层术与扫描电镜图像的黄土微结构定量分析[J]. 岩土力学，2012，33(1)：243–247.(WANG Huini，NI Wankui. Quantitative analysis of loess microstructure based on CT and SEM images[J]. Rock and Soil Mechanics，2012，33(1)：243–247.(in Chinese))
[28] GIMENEZ R G，DE LA VILLA R V，MARTIN J A G. Characterization of loess in central Spain：a microstructural study[J]. Environmental Earth Science，2012，65(7)：2 125–2 137.
[29] 陈国兴，樊良本，陈 甦，等. 土质学与土力学[M]. 北京：中国水利水电出版社，2009：82.(CHEN Guoxing，FAN Liangben，CHEN Su，et al. Soil science and soil mechanics[M]. Beijing：China Water Resources and Hydropower Press，2009：82.(in Chinese))
[30] 刘奉银，吉嶺充俊，车爱兰，等. Q3黄土力学各向异性特性的初步试验研究[C]// 中国岩石力学与工程学会第七次学术大会论文集. [S. l.]：[s. n.]，2002：129–131.(LIU Fengyin，JI Ling Chong Jun，CHE Ailan，et al. Preliminary experimental study on the mechanics anisotropy characteristics of Q3 loess[C]// Proceedings of the 7th Academic Conference of the Chinese Society of Rock Mechanics and Engineering. [S. l.]：[s. n.]，2002：129–131.(in Chinese))
[31] FANG Q，HONG H L，ZHAO L L，et al. Tectonic uplift-influenced monsoonal changes promoted hominin occupation of the Luonan Basin：Insights from a loess-paleosol sequence，eastern Qinling Mountains，central China[J]. Quaternary Science Reviews，2017，169：312–329.
[32] 申春妮，方祥位，王和文，等. 吸力、含水量和干密度对重塑非饱和土抗剪强度影响研究[J]. 岩土力学，2009，30(5)：1 347–1 351. (SHEN Chunni，FANG Xiangwei，WANG Hewen，et al. Effect of suction，water content and dry density on shear strength of remolded unsaturated soil[J]. Rock and Soil Mechanics，2009，30(5)：1 347–1 351.(in Chinese))
[33] 贾 亮，朱彦鹏，朱鋆川. 兰州马兰、离石压实黄土抗剪强度影响因素探讨[J]. 岩土工程学报，2014，36(增2)：120–124.(JIA Liang，ZHU Yanpeng，ZHU Junchuan. Discussion on the influencing factors for shear strength about Malan and Lishi compacted loess in Lanzhou[J]. Chinese Journal of Geotechnical Engineering，2014，36(Supp.2)：120–124.(in Chinese))
2019, Vol. 38 
