Farming Influence on Physical-Mechanical Properties and Microstructural Characteristics of Backfilled Loess Farmland in Yan’an, China

Lina Ma, Shengwen Qi, Bowen Zheng, Songfeng Guo, Qiangbing Huang and Xinbao Yu
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Lina Ma: Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beituchengxilu 19, Chaoyang District, Beijing 100029, China
Shengwen Qi: Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beituchengxilu 19, Chaoyang District, Beijing 100029, China
Bowen Zheng: Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beituchengxilu 19, Chaoyang District, Beijing 100029, China
Songfeng Guo: Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beituchengxilu 19, Chaoyang District, Beijing 100029, China
Qiangbing Huang: Department of Geological Engineering, Chang’an University, Xi’an 710054, China
Xinbao Yu: Department of Civil Engineering, University of Texas at Arlington, 416 Yates St., Arlington, TX 76019, USA

Sustainability, 2020, vol. 12, issue 14, 1-18

Abstract: A gigantic project named Gully Land Consolidation (GLC) was launched in the hill-gully region of the Chinese Loess Plateau in 2011 to cope with land degradation and create new farmlands for cultivation. However, as a particular kind of remolded loess, the newly created and backfilled farmland may bring new engineering and environmental problems because the soil structure was disturbed and destroyed. In this study, current situations and characteristics of GLC are introduced. Test results show that physical-mechanical properties and microstructural characteristics of backfilled loess of one-year and five-year farmland are significantly affected by the Gully Land Consolidation project. Compared to natural loess, the moisture content, density, and internal friction angle of backfilled loess increase. On the contrary, the porosity, plasticity index, particle size index, and cohesion index decrease. Through SEM tests, it is observed that the particles of backfilled loess are rounded, with large pores filled with crushed fine particles, which results in skeleton strength weakness among particles and pores. The pore size distribution (PSD) of the four types of loess (Q 3 loess, Q 2 loess, one-year farmland, and five-year farmland) was measured using mercury intrusion porosimetry (MIP) tests, showing that the pore size of Q 3 loess is mainly mesopores 4000–20,000 nm in size, accounting for 67.5%. The Q 2 , five-year, and one-year farmland loess have mainly small pores 100–4000 nm in size, accounting for 52.5%, 51.7%, and 71.7%, respectively. The microscopic analysis shows that backfill action degrades the macropores and mesopores into small pores and micropores, leading to weak connection strength among soil particles, which further affects the physical-mechanical properties of loess. The disturbance of backfilled loess leads to an obvious decrease in cohesion and a slight increase in internal friction compared to natural loess. The farming effect becomes prominent with increased backfill time, while the loess soil moisture content increases gradually. Both the cohesion and internal friction of the backfilled loess soil decrease to different degrees. This study is helpful to investigate sustainable land use in the Chinese Loess Plateau and similar areas.

Keywords: Gully Land Consolidation; backfilled loess; physical-mechanical property; microstructural characteristic; pore size distribution (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2020
References: View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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