红壤坡耕地耕层土壤抗剪强度及影响因素响应特征

发布时间：2018-05-18 02:26

本文选题：红壤 + 坡耕地　；参考：《西南大学》2017年硕士论文

【摘要】：土壤抗剪强度与土壤侵蚀关系非常密切,是表征土壤抗侵蚀性能,土体破坏、埂坎稳定性重要力学指标,同时也是土壤耕性的重要参数。本文以江西进贤、云南马龙、广西来宾红壤坡耕地为研究对象,研究了耕层土壤理化性质和抗剪强度变化特征,通过Pearson相关分析法和主成分分析探讨影响抗剪强度的因素,采用室内模拟实验对比研究三种红壤坡耕地耕层土壤抗剪强度对土壤含水率、干湿循环次数、幅度、土壤容重、粒径级配的响应特征,以期为红壤坡耕地耕层土壤水土流失防治、耕层土壤质量改善和梯田埂坎稳定性提供理论借鉴。主要结论如下:(1)不同类型红壤坡耕地不同土层土壤理化性质差异明显。江西进贤红壤、广西来宾红壤、云南马龙红壤坡耕地不同土层土壤容重和孔隙度差异明显,土壤容重表现为:耕作层(0—20 cm)心土层(20—40 cm)底土层(40—60 cm),毛管孔隙度和总孔隙度表现为耕作层心土层底土层(P0.05)。耕作层土壤初始入渗率、稳定入渗率显著高于心土层、底土层。不同土层土壤颗粒以粉粒、砂粒为主,土壤质地为壤土,土壤机械稳定性团聚体以5 mm、5-2 mm粒级团聚体为主,土壤水稳定性团聚体以0.5-0.25mm和0.25mm粒级团聚体为主,土壤微团聚体以0.25~0.05 mm、0.05~0.01 mm粒级为主。不同土层土壤有机质、全氮、全磷、碱解氮、有效磷含量差异显著,随土层深度增加而含量降低,表现为耕作层心土层底土层。综合野外调查和试验分析,红壤坡耕地合理耕层主要特征表现为:土壤容重介于1.11~1.25g/cm-3,总孔隙度56%,土壤稳定入渗率5.88~10.18mm/min,土壤质地为壤土,有机质含量13.67g/kg。(2)不同类型红壤坡耕地土壤抗剪强度差异明显,随土层深度增加而增大,呈现阶段性特征,30-40 cm土层时抗剪强度迅速减小。江西进贤红壤、云南马龙红壤Ⅰ阶段:0-40 cm耕层,抗剪强度随深度呈线性递增,Ⅱ阶段:40-60 cm土层,抗剪强度随土层深度增加趋于出一定的稳定性。广西来宾红第Ⅰ阶段:0-30 cm土层,抗剪强度随深度呈线性递增,Ⅱ阶段:30-60 cm土层,抗剪强度增加幅度急剧减小,趋于稳定。综合野外调查结果,红壤坡耕地合理耕层抗剪强度变化范围为3.58~5.99 kPa根据Pearson相关和主成分分析表明,土壤容重、含水率、物理性粘粒、分散系数、湿筛MWD是与红壤坡耕地土壤抗剪强度密切相关的物理性因素,土壤有机质、全氮、全磷、有效磷、碱解氮是与红壤坡耕地土壤抗剪强度密切相关的化学性因素。(3)不同类型红壤坡耕地土壤抗剪强度随含水率呈非线性衰减,不同垂直荷载下抗剪强度随含水率衰减路径差异明显。江西进贤红壤100 kPa、200 kPa下,随含水量增加抗剪强度微幅度波动衰减,300 kPa、400 kPa下,含水率为11%~19%时,趋于稳定,含水率为19%~23%时,抗剪强度剧烈衰减,含水率为23%~27%时,抗剪强度趋于稳定。广西来宾红壤200、300、400kPa下,呈非线性阶段衰减,含水率为11%~17%时,呈非线性平滑衰减,含水率为17%~27%时,呈非线性波动衰减。云南马龙红壤抗剪强度随含水率呈非线性波动衰减,含水率25%时,衰减趋势减弱并趋于稳定。不同类型红壤坡耕地耕层土壤粘聚力随含水率先增大而后减小,内摩擦角随含水率增大呈非线性波动衰减。含水率为11%~21%时,江西进贤红壤粘聚力介于1.02~16.54 kPa,含水率21%时,粘聚力随含水率增加而减小。含水率11%~23%时,广西来宾红壤、云南马龙红壤粘聚力迅速增大,含水率23%时,随含水率增加逐渐衰减。江西进贤红壤、广西来宾红壤、云南马龙红壤含水率低于19%、17%、15%时,内摩擦角线性衰减,含水率超过转折点时,摩擦角波动衰减,且趋于稳定。(4)江西进贤红壤与云南马龙红壤坡耕地耕层土壤抗剪强度、粘聚力随循环次数增加呈非线性衰减,内摩擦角呈波动式衰减。对江西进贤红壤与云南马龙红壤抗剪强度而言,Ⅰ阶段1~3、4次循环,抗剪强度衰减率呈近似线性迅速增加,抗剪强度衰减快,Ⅱ阶段3、4~5次循环,抗剪强度逐渐趋于稳定值。对粘聚力而言,Ⅰ阶段0~3、4次循环,呈现近似线性地迅速衰减;Ⅱ阶段为3、4~5次循环,粘聚力趋于稳定。内摩擦角随干湿循环次数增加波动式衰减,但衰减幅度明显低于粘聚力。循环次数、幅度交互效应下,江西进贤红壤粘聚力随循环次数的增大先迅速减小,波动范围为2.65~9.75 Kpa,循环次数3次后,粘聚力趋于稳定,而循环幅度对粘聚力衰减作用不显著。江西进贤红壤内摩擦角随干湿循环幅度增大而增大。云南马龙红壤粘聚力随循环次数增加而减小,随循环幅度变化先微幅增大后减小,峰值出现在Δw=15%附近,内摩擦角随循环次数增加而波动式减小,随干湿循环幅度变化衰减路径起伏波动大,衰减受干湿循环幅度影响小。(5)江西进贤红壤、广西来宾红壤、云南马龙红壤坡耕地耕层土壤粘聚力随着容重增加呈逐渐增大趋势。粒径级配对红壤坡耕地耕层土壤粘聚力无显著影响,内摩擦角随0.05mm细粒径颗粒的增加而增大,内摩擦分布范围为7.57°~8.67°、7.38°~8.67°、8.97°~9.33°。容重较小时(0.9~1.1g/cm3),粘聚力随容重平稳增加,容重较大时(1.1~1.3g/cm3),粘聚力随容重陡增。云南马龙红壤粘聚力随容重呈现波动式增加,粘聚力分布1.85~3.33 kPa,内摩擦角随着容重增加呈现出逐渐增大趋势。
[Abstract]:Soil erosion resistance is very closely related to soil erosion. It is an important mechanical index to characterize soil erosion resistance, soil destruction, and ridge stability. It is also an important parameter for soil tillage. This paper studies the soil physical and chemical properties and shear strength changes of soil in Jinxian, Yunnan, Yunnan, Jiangxi and Guangxi Laibin red soil. By means of Pearson correlation analysis and principal component analysis, the factors affecting the shear strength were discussed. The response characteristics of soil moisture content, dry and wet cycle times, amplitude, soil bulk density and grain size distribution of three kinds of red soil sloping cultivated land soil were studied by indoor simulation experiments, so as to be the soil soil and water soil in red soil slope farmland. The main conclusions are as follows: (1) there are obvious differences in soil physical and chemical properties of different soil layers in different types of red soil, Jiangxi Jinxian red soil, Guangxi Laibin red soil, and the soil bulk density and porosity of different soil layers in the Malone red soil slope farmland in Yunnan, and the soil bulk density The soil layer (0 - 20 cm) soil layer (20 - 40 cm) soil layer (40 - 60 cm), the capillary porosity and total porosity is shown as the soil layer soil layer (P0.05) of the tillage layer. The initial infiltration rate of the tillage soil, the stable infiltration rate is significantly higher than the soil layer, the bottom soil layer. The soil particles in different soil layers are mainly powder and sand, and soil texture is loam soil. Soil water stability aggregates are mainly composed of 5 mm and 5-2 mm granular aggregates, and soil water stability aggregates are dominated by 0.5-0.25mm and 0.25mm particles. The soil microaggregates are mainly 0.25~0.05 mm and 0.05~0.01 mm particles. The soil organic matter, total nitrogen, total phosphorus, alkali hydrolysable nitrogen, and available P content have significant difference with the depth of soil layer. The main characteristics of rational plough in red soil slope arable land are as follows: soil bulk density is 1.11~1.25g/cm-3, total porosity is 56%, soil stable infiltration rate is 5.88~10.18mm/min, soil texture is loam, organic matter content is 13.67g/kg. (2) different types of red soil slope cultivated land. The difference of soil shear strength is obvious, which increases with the depth of soil layer, showing stage characteristics, the shear strength of 30-40 cm soil layer decreases rapidly. Jiangxi Jinxian red soil, Yunnan Malone red soil I stage: 0-40 cm plough layer, the shear strength is linearly increasing with depth, stage II: 40-60 cm soil layer, the shear strength tends to increase with soil depth to a certain extent. The stability of Guangxi Laibin red stage I: 0-30 cm soil layer, the shear strength is linearly increasing with the depth, stage II: 30-60 cm soil layer, the increasing amplitude of shear strength decreases sharply and tends to stability. Comprehensive field investigation results show that the change of shear strength of reasonable plough in red soil slope farmland is 3.58~5.99 kPa based on Pearson correlation and principal component analysis table The soil bulk density, water content, physical clay particles, dispersion coefficient, wet sieve MWD are closely related to the soil shear strength of red soil slope farmland. Soil organic matter, total nitrogen, total phosphorus, effective phosphorus, alkali hydrolysable nitrogen are chemical factors closely related to soil shear strength of red soil slope farmland. (3) soil shear strength of different types of red soil slope farmland There is a nonlinear attenuation with water content, and the difference of shear strength with water content decreases obviously under different vertical loads. Under 100 kPa kPa and 200 kPa, the shear strength decreases with the moisture content increasing, the shear strength decreases, 300 kPa and 400 kPa, when the water content is 11%~19%, and the moisture content is 19%~23%, the shear strength attenuates violently. When the water rate is 23%~27%, the shear strength tends to be stable. Under the 200300400kPa of Guangxi Laibin red soil, the attenuation is nonlinear stage. When the water content is 11%~17%, it is nonlinear and smooth attenuation. When the water content is 17%~27%, it is nonlinear wave attenuation. The shear strength of Malone red soil in Yunnan is attenuated with the moisture content, and the attenuation trend is 25% when water content is water. The cohesive force of the plough soil in different types of sloping farmland is first increased and then decreased with water content, and the internal friction angle decreases with the increase of water content. When the water content is 11%~21%, the cohesion of the red soil in Jinxian, Jiangxi is 1.02~16.54 kPa, and the cohesion decreases with the increase of water content when the water content is 21%. The water content is 11%~23% When Guangxi Laibin red soil, Yunnan Malone red soil cohesive force increased rapidly, when water content was 23%, it gradually attenuated with the increase of water content. The water content of Jiangxi Jinxian red soil, Guangxi Laibin red soil, Yunnan Malone red soil was lower than 19%, 17%, 15%, the internal friction angle linearly attenuated, when water content exceeded the turning point, the friction angle fluctuation attenuated and tended to stabilize. (4) Jiangxi entered The shear strength of the soil of cultivated soil in red soil and Yunnan Malone red soil slope is nonlinear attenuation with the increase of cycle times, and the internal friction angle is fluctuant. For the shear strength of Jinxian red soil and Yunnan Malone red soil in Yunnan, the shear strength attenuation rate is approximately linear and fast increasing, and the shear strength attenuates fast in the Jiangxi Jinxian red soil and Yunnan red soil. As for the 3,4~5 secondary cycle, the shear strength gradually tends to a stable value. For cohesion, the 0~3,4 secondary cycle of stage I is approximately linear and rapidly attenuates; the second stage is 3,4~5 secondary cycle, and the cohesion tends to be stable. The internal friction angle increases with the frequency of dry and wet cycle, but the attenuation amplitude is obviously lower than that of cohesive force. Under the mutual effect, the cohesive force of red soil in Jinxian of Jiangxi rapidly decreases with the increase of cycle times, and the fluctuation range is 2.65~9.75 Kpa. After 3 cycles, the cohesive force tends to be stable, and the cyclic amplitude is not significant to the cohesive force attenuation. The internal friction angle of the red soil in Jinxian of Jiangxi is increased with the increase of the dry and wet circulation amplitude. The cohesion of the red soil in Yunnan Malone soil follows the cohesion of the red soil. The cycle number increases and decreases with the increase of the amplitude of the cycle, the peak appears near the delta w=15%, the internal friction angle decreases with the increase of the cycle number. The attenuation path fluctuates with the dry and wet cycle amplitude, and the attenuation is less affected by the dry and wet cycle. (5) Jiangxi Jinxian red soil, Guangxi Laibin red soil, Yunnan horse The cohesive force of the soil in the cultivated land on the slope of the red soil slope increased gradually with the increase of the bulk density. There was no significant influence on the cohesive force of the soil in the plough layer of the red soil slope. The internal friction angle increased with the increase of the 0.05mm fine particle size, and the distribution range of internal friction was 7.57 ~8.67, 7.38 [8.67], 8.97 [~9.33]. The bulk density was lower (0.9~1.1g/cm3). Cohesion increases steadily with bulk density, the cohesive force increases with bulk density when the bulk density is larger (1.1~1.3g/cm3). The cohesive force of Yunnan Malone red soil increases with the bulk density, and the cohesive force distributes 1.85~3.33 kPa, and the internal friction angle increases gradually with the increase of bulk density.
【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S157

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