Effects of mud with rice straw as slope protection material on the water migrationin highway subgrade
ZHANG Hongri, WANG Guiyao, LAN Sulian, XIA Yiqi, SHA Linchuan
1. School of Civil Engineering and Architecture, Changsha University of Science＆Technology, 410076, Changsha, China; 2. Guangxi Transportation Research & Consulting Co., Ltd., 530007, Nanning, China
Abstract：[Background] In the southern China moist region, rainwater infiltration of slope surface and water migration in subgrade are the main factors for its bearing capacity degradation. Lacking protection will lead to cracking or excessive erosion on slope surface. In order to reduce water content changing in subgrade in sunny or rainy weather, a new material consisting of clay and rice straw is developed, and its application for slope protection is probed in this paper. [Methods] Firstly, the mud with rice straw was prepared by mixing the shredded clay with water and rice straw in 5-10 cm. And then the permeability coefficient and anti-penetrability performance of compacted clay, pure mud, mud with rice straw and vegetation was determined by variable head permeability test and impermeability test. Afterwards, an indoor-test simulating embankment slope in continuous natural radiation and continuous slope scouring was executed to probe soil moisture inside subgrade in condition 1: bare slope, condition 2: slope under the protection of pure mud, condition 3: slope under the protection of mud with rice straw, condition 4: condition 2 + grass seeds, and condition 5: condition 3 + grass seeds. Through the sampling test of the water content distribution in subgrade center of 60 cm horizontal depth under above conditions, the water migration characteristics of the subgrade under extreme weather conditions were studied. [Result] The permeability coefficient of the material of mud with rice straw was 0.81×10-5 cm/s. The permeation time of mud with rice straw and vegetation samples was 21 h in the 4th and 5th dry-wet cycle penetration tests. In the dry weather condition, the moisture content of the mud decreased to 13.6% after 50 days in condition 3, and the moisture content was 17.2%-21.4% after 50 days in condition 5 in which the water content of the soil was stable. In the heavy rainfall scouring test, the water content of the condition 3 and condition 4 was only slightly increased at the 6th hour, while the water content of the soil in the horizontal depth of 20 cm was slightly increased in condition 5. [Conclusions] Mud with rice straw presents small permeability coefficient and optimal permeability. The mud cracks was reduced in dry weather and soil moisture was effectively maintained, what was beneficial to the plant growth. The mud with rice straw can improve the moisture migration performance in slope surface under heavy rainfall erosion, and keep the stability of the internal moisture content in subgrade. After the vegetation root growth and development, it can form a green ecological environmental protection system, thus, it has a great significance to highway ecological construction.
张红日1,2, 王桂尧1, 兰素恋2, 夏旖琪1,2, 沙琳川1. 稻秸秆泥皮护坡材料对路基水分迁移影响的初步研究[J]. 中国水土保持科学, 2017, 15(2): 146-152.
ZHANG Hongri, WANG Guiyao, LAN Sulian, XIA Yiqi, SHA Linchuan. Effects of mud with rice straw as slope protection material on the water migrationin highway subgrade. SSWC, 2017, 15(2): 146-152.
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2017, Vol. 15 
