本文關(guān)鍵詞： 崩崗洪積扇 根系 根土復(fù)合 抗拉強(qiáng)度 抗剪強(qiáng)度　出處：《福建農(nóng)林大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：為探討草本植物根系對(duì)崩崗洪積扇土壤的固土力學(xué)特性,本文以巨菌草及寬葉雀稗為研究對(duì)象,采用根系拉根試驗(yàn)、原位剪切試驗(yàn)、室內(nèi)直剪試驗(yàn)分析根系抗拉特性及根系對(duì)根土復(fù)合體抗剪強(qiáng)度的影響。研究結(jié)果如下:(1)草本及裸地的土壤自然含水率均隨土層深度的增加而表現(xiàn)為遞減的趨勢(shì),而各措施的土壤容重均隨土層深度增加而表現(xiàn)為遞增的趨勢(shì)。巨菌草和寬葉雀稗的根系均主要分布在0—5 cm 土層,隨著土層深度的增加,巨菌草各根系參數(shù)表現(xiàn)為對(duì)數(shù)函數(shù)形式降低,而寬葉雀稗的根系參數(shù)則表現(xiàn)為線性函數(shù)形式降低。兩種草本植物均以0.5 mm徑級(jí)根系為主,且巨菌草細(xì)根比寬葉雀稗細(xì)根更多。(2)根系直徑與拉伸標(biāo)距對(duì)根系極限抗拉力與抗拉強(qiáng)度的影響顯著,而拉伸速率則對(duì)這兩種草本植物根系的抗拉特性影響不顯著。兩種草本植物根系的單根極限抗拉力隨直徑的增加呈冪函數(shù)增加,而其單根抗拉強(qiáng)度則隨直徑的增大呈冪函數(shù)形式減小。寬葉雀稗根系的單根極限抗拉力與抗拉強(qiáng)度隨標(biāo)距增加而減小,但巨菌草根系在5 cm的標(biāo)距下表現(xiàn)出最強(qiáng)的抗拉強(qiáng)度。當(dāng)拉伸條件相同時(shí),巨菌草極限抗拉力及抗拉強(qiáng)度高于寬葉雀稗,說(shuō)明巨菌草較寬葉雀稗擁有更強(qiáng)抵抗外力拉伸的能力。(3)野外原位剪切試驗(yàn)表明,寬葉雀稗和巨菌草均能提高崩崗洪積扇土壤的抗剪強(qiáng)度,且巨菌草的效果更明顯;隨土層深度的增加,巨菌草的抗剪強(qiáng)度呈對(duì)數(shù)函數(shù)減小,而寬葉雀稗呈指數(shù)形式降低。在0—20 cm各土層,兩草種抗剪強(qiáng)度均顯著大于裸地。崩崗洪積扇土壤的抗剪強(qiáng)度與巨菌草及寬葉雀稗根系的生物量密度、根表面積密度和分叉數(shù)密度極顯著正相關(guān),與根長(zhǎng)密度顯著正相關(guān)。通過(guò)逐步回歸分析可知,草本植物根系的生物量密度是影響崩崗洪積扇土壤抗剪強(qiáng)度的主導(dǎo)因子。室內(nèi)直剪試驗(yàn)表明,在土壤條件相同的情況下,根系直徑對(duì)根土復(fù)合體抗剪強(qiáng)度的影響不顯著。隨著根重密度的增大,根土復(fù)合體抗剪強(qiáng)度增大,但僅當(dāng)根重密度達(dá)到一定值時(shí),根系對(duì)增強(qiáng)土壤抗剪強(qiáng)度的效果才明顯;根土復(fù)合體的內(nèi)摩擦角和粘聚力也隨根重密度的增大而增大。根面積比率能表征巨菌草和寬葉雀稗根土復(fù)合體抗剪強(qiáng)度的強(qiáng)弱。綜上,巨菌草及寬葉雀稗根系均有增強(qiáng)崩崗洪積扇土壤抗剪強(qiáng)度的能力,且巨菌草強(qiáng)于寬葉雀稗。因此,這兩種草本植物在崩崗侵蝕區(qū)值得推廣。
[Abstract]:In order to study the soil mechanics characteristics of herbaceous root system on the soil of alluvial fan, the root pulling root test and in situ shear test were used to study the soil properties of giant fungi and paspalum paspalum. The tensile properties of root system and the effect of root system on the shear strength of root soil complex were analyzed by direct shear test in laboratory. The results are as follows: 1). The natural soil moisture content of herbaceous and bare land decreased with the increase of soil depth. The soil bulk density of each measure increased with the increase of soil depth, and the root system of megaterium and paspalum were mainly distributed in 0-5 cm soil layer, with the increase of soil depth. The root system parameters of macrobacillus decreased in the form of logarithmic function, while the root parameters of Paspalum grandii decreased in the form of linear function. The root system of the two herbaceous plants was mainly 0.5 mm diameter root system. And the fine root diameter and the extension distance of the fine root of megaterium were more than that of the fine root of Paspalum paspalum, and the effects of the diameter and the extension distance on the ultimate tensile strength and the tensile strength of the root system were significant. However, the tensile rate had no significant effect on the tensile properties of the two herbaceous roots. The single root ultimate tensile strength of the two herbaceous roots increased with the increase of the diameter. However, the single root tensile strength decreased with the increase of diameter, while the single root ultimate tensile strength and tensile strength decreased with the increase of the distance. But the root system showed the strongest tensile strength at a distance of 5 cm. When the stretching conditions were the same, the ultimate tensile strength and tensile strength of the giant grass were higher than that of paspalum paspalum. The results of field in situ shear test showed that both Paspalum grandifolia and Macrobacillus could improve the shear strength of the soil of flood fan. And the effect of giant fungus is more obvious. With the increase of soil depth, the shear strength of Giant fungus decreased as logarithmic function, while that of Paspalum grandifolia decreased exponentially in 0-20 cm soil layer. The shear strength of the two herbaceous species was significantly higher than that of bare land. The shear strength of the alluvial fan soil was positively correlated with the biomass density, root surface area density and branching number density of the root system of Giant fungus and Paspalum paspalum. Through stepwise regression analysis, the biomass density of herbaceous plant roots was the main factor affecting the shear strength of alluvial fan soil. The direct shear test in laboratory showed that the root biomass density of herbaceous plants was the main factor that affected the shear strength of alluvial fan soil. Under the same soil conditions, root diameter had no significant effect on the shear strength of root soil complex. With the increase of root weight density, the shear strength of root soil complex increased, but only when the root weight density reached a certain value. The effect of root system on strengthening soil shear strength was obvious. The internal friction angle and cohesive force of root soil complex also increased with the increase of root weight density. The ratio of root area can indicate the shear strength of the root soil complex. Both the root system of macrobacillus and paspalum grandifolia have the ability to enhance the shear strength of the toppling flood fan soil, and the giant grass is stronger than the paspalum. Therefore, these two herbaceous plants are worth popularizing in the area of collapse erosion.
【學(xué)位授予單位】：福建農(nóng)林大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：S157.43

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