本文關(guān)鍵詞： 喬木根系 軸向疲勞拉伸 抗拉強(qiáng)度 三軸壓縮試驗(yàn) 土壤抗剪強(qiáng)度　出處：《北京林業(yè)大學(xué)》2013年博士論文　論文類(lèi)型：學(xué)位論文

【摘要】：森林生態(tài)系統(tǒng)中的根系有固持植物體、吸收水分和溶于水中的礦物質(zhì)的作用,同時(shí)還能夠阻止淺層滑坡、固持水土。本文通過(guò)對(duì)華北土石山區(qū)4種常見(jiàn)喬木：油松、落葉松、白樺和蒙古櫟根系進(jìn)行軸向疲勞拉伸試驗(yàn),測(cè)定其疲勞前后的抗拉力學(xué)特性；分析了直徑、樹(shù)種等因素對(duì)根系疲勞前后對(duì)最大抗拉力、抗拉強(qiáng)度和應(yīng)力-應(yīng)變關(guān)系的影響；然后,選取4個(gè)樹(shù)種直徑3、5、7mm根系作為試驗(yàn)根樣與華北木蘭圍場(chǎng)取回的土樣一起制備成根—土復(fù)合體試樣,采用全自動(dòng)三軸壓縮儀對(duì)復(fù)合體進(jìn)行剪切試驗(yàn),對(duì)復(fù)合體的剪切特性進(jìn)行研究分析,評(píng)價(jià)根系直徑、樹(shù)種和不同分布方式對(duì)土壤抗剪強(qiáng)度的增強(qiáng)作用。 主要研究成果如下： (1)疲勞前4種喬木根系最大抗拉力的平均值大小順序?yàn)椋喊讟迕晒艡涤退陕淙~松。循環(huán)10000次前后油松的抗拉力變化最大,其次是落葉松和蒙古櫟,變化最小的是白樺。疲勞后4種喬木根系最大抗拉力平均值大小順序?yàn)椋好晒艡蛋讟逵退陕淙~松。 (2)4個(gè)樹(shù)種根系疲勞前抗拉強(qiáng)度隨著直徑的增加而減小,成冪函數(shù)關(guān)系；4個(gè)樹(shù)種的抗拉強(qiáng)度排序?yàn)榘讟迕晒艡涤退陕淙~松。經(jīng)過(guò)10000次疲勞拉伸試驗(yàn)后,4種喬木根系抗拉強(qiáng)度順序是：白樺蒙古櫟≈油松落葉松。這與疲勞前順序基本沒(méi)有變化,說(shuō)明疲勞對(duì)樹(shù)種單根抗拉強(qiáng)度有所影響但不足以改變物種本身根系結(jié)構(gòu)組成所造成的影響,樹(shù)種依舊是影響根系抗拉強(qiáng)度特性非常重要的因素。植物根系在10000次疲勞后的最大抗拉力和抗拉強(qiáng)度均比循環(huán)前相同根徑的大,說(shuō)明根系在自然界中的水流或者暴風(fēng)等破壞力的低周疲勞作用下,自身的抗拉性能不但沒(méi)有降低,其抗拉性能有不同程度的增加,增強(qiáng)了根系的固土能力。 (3)三軸壓縮試驗(yàn)結(jié)果表明根系能明顯有效地提高土壤的抗剪強(qiáng)度。分布在土體中根系直徑增加,根—土復(fù)合體的內(nèi)摩擦角和內(nèi)粘聚力也隨之增大,土壤抗剪強(qiáng)度加強(qiáng),加根能夠明顯提高土體抵抗剪切破壞的能力。 (4)根系這種增強(qiáng)作用與根系直徑及其在土樣中的分布方式有很大關(guān)系。復(fù)合根復(fù)合體抗剪強(qiáng)度值較其他兩種分布方式抗剪強(qiáng)度有明顯增加。在水平根、垂直根和復(fù)合根三種復(fù)合體抗剪強(qiáng)度增加順序基本遵循復(fù)合根復(fù)合體垂直根復(fù)合體水平根復(fù)合體。說(shuō)明復(fù)合根在增強(qiáng)土體強(qiáng)度方面效果最為顯著,說(shuō)明植物根系在土壤中形成橫縱交錯(cuò)的狀態(tài)對(duì)減少滑坡等自然災(zāi)害方面起到更好的作用。
[Abstract]:The roots of the forest ecosystem hold the plants, absorb water and minerals dissolved in the water, and prevent shallow landslides. In this paper, the axial fatigue tensile tests of four common trees: Pinus tabulaeformis, Larix olgensis, Bai Hua and Quercus mongolica were carried out to determine their tensile properties before and after fatigue. The effects of diameter and tree species on the maximum tensile strength, tensile strength and stress-strain relationship before and after root fatigue were analyzed. Then, four tree species with diameter of 3 ~ 5 ~ 5 ~ 7 mm were selected as experimental root samples and soil samples collected from Magnolia chinensis paddock in North China to form root-soil complex samples. The shear test of the complex was carried out with automatic triaxial compression apparatus, and the shear characteristics of the complex were studied and analyzed to evaluate the enhancement of soil shear strength by root diameter, tree species and different distribution patterns. The main findings are as follows: 1) the mean order of the maximum tensile strength of the four tree roots before fatigue was Bai Hua Quercus mongolica larch, and the tensile strength of Pinus tabulaeformis changed the most before and after 10000 cycles. The second was Larix gmelini and Quercus mongolica, and the least change was Bai Hua. After fatigue, the order of the mean values of the maximum tensile strength of root system of four species of Arbor was as follows: Bai Hua larch of Mongolian Quercus mongolica. (2) the tensile strength of four tree species before fatigue decreased with the increase of diameter, and the power function relation; The order of tensile strength of four tree species was Bai Hua Quercus mongolica Larix after 10000 fatigue tensile tests. The order of root tensile strength of four species of trees was Bai Hua Mongolian Quercus 鈮，

本文編號(hào)：1454525