本文關(guān)鍵詞：西南丘陵山區(qū)農(nóng)村道路構(gòu)建及其景觀效應(yīng)，，由筆耕文化傳播整理發(fā)布。

        近年來,農(nóng)村道路作為農(nóng)村基礎(chǔ)設(shè)施建設(shè)重點之一,在農(nóng)村土地綜合整治、新農(nóng)村建設(shè)、城鄉(xiāng)統(tǒng)籌發(fā)展平臺上,得到了迅猛擴展。目前,對大地貌單元內(nèi)高等級道路系統(tǒng)關(guān)注較多,如高速公路、鐵路、國(省)道或縣道等路網(wǎng)聯(lián)貫對沿線物流和信息交換的集聚與輻射,所具有“通道-阻隔”效應(yīng)對大地貌單元地表覆被和景觀利用的異質(zhì)性和多樣性的驅(qū)動及其對生態(tài)系統(tǒng)的影響。低等級的農(nóng)村道路則集中于道路網(wǎng)布局與評價、道路工程設(shè)計與造價的控制、工程施工與質(zhì)量監(jiān)管、養(yǎng)護管理、以及路面排水、邊坡水土流失與道路侵蝕防治等方面的研究。然而,在西南丘陵山區(qū)廣泛分布的農(nóng)村道路,不僅受到人為經(jīng)濟活動的影響,而且深受自然環(huán)境條件的制約,農(nóng)村道路建設(shè)及其運營過程為社會發(fā)展提供保障,促進經(jīng)濟發(fā)展的同時,也帶來了自然景觀和生態(tài)系統(tǒng)的分割、干擾、破壞、退化等景觀生態(tài)問題。為此,本文通過實地調(diào)研西南丘陵山區(qū)農(nóng)村道路現(xiàn)狀,選取了四川省雅安市蘆山縣飛仙關(guān)鎮(zhèn)鳳凰、三友2個行政村(樣區(qū)Ⅰ),貴州省桐梓縣九壩鎮(zhèn)白鹽井、水河、槐子3個行政村(樣區(qū)Ⅱ),重慶市合川區(qū)大石鎮(zhèn)高川、柿子、竹山、懣井4個行政村(樣區(qū)Ⅲ),重慶市秀山土家族苗族自治縣梅江鎮(zhèn)新聯(lián)、關(guān)田2個行政村(樣區(qū)Ⅳ)和重慶市忠縣拔山鎮(zhèn)拔山、石聯(lián)、蘇家3個行政村(樣區(qū)V)等五個樣區(qū),分析了不同地形地貌、水文地質(zhì)、氣候、土壤、植被等地理環(huán)境和農(nóng)業(yè)人口、耕地數(shù)量、人均耕地、基礎(chǔ)設(shè)施、農(nóng)業(yè)生產(chǎn)條件、耕作制度和經(jīng)濟發(fā)展水平等社會經(jīng)濟綜合要素融合下的農(nóng)村道路類型與功能,明確了西南丘陵山區(qū)經(jīng)濟發(fā)展的現(xiàn)狀及其未來發(fā)展態(tài)勢對農(nóng)村道路的需求,結(jié)合當?shù)剞r(nóng)業(yè)機械使用狀況及常用建材特色,研究了農(nóng)村道路路面(基)控制等結(jié)構(gòu)層次工程設(shè)計技術(shù),構(gòu)建西南丘陵山區(qū)農(nóng)村道路體系,分析了農(nóng)村道路體系的網(wǎng)絡(luò)特征和景觀效應(yīng),從而為西南丘陵山區(qū)農(nóng)村道路體系布局與設(shè)計提供理論和技術(shù)支撐。(1)農(nóng)村道路布局農(nóng)村道路按功能和路面寬度可分為田間道和生產(chǎn)路兩級。田間道應(yīng)沿田塊的短邊布設(shè),在旱作地區(qū),田間道也可布設(shè)在作業(yè)區(qū)的中間,沿田塊的長邊布設(shè),使耕作機械兩邊均可進入工作小區(qū)以減少空行。在梯田區(qū)布置田間道應(yīng)按照具體地形,采取通梁聯(lián)峁,沿溝走邊的方法布設(shè)。田間道多設(shè)置在溝邊、溝底或山峁的脊梁上。山低坡緩,田間道呈斜線形；山高坡陡,田間道可呈“S”形、“之”字形或螺旋形迂回上山；生產(chǎn)路宜縱橫交錯布置,因地制宜地與田間道形成網(wǎng)狀,設(shè)在田塊的長邊,并分旱地區(qū)和水田區(qū)采取不同的方式布置。旱地橫向生產(chǎn)路為40～200m,布置一條生產(chǎn)路。在石坎較多的地區(qū)可與石坎結(jié)合設(shè)置,以節(jié)約用地�？v向生產(chǎn)路多布置在丘陵山地的脊部,根據(jù)田面長度,一般200～500m布置一條。如果生產(chǎn)路與溝渠組合設(shè)置不利于排水或不利于通行時,應(yīng)分開布置。水田生產(chǎn)路可設(shè)置在農(nóng)溝外側(cè)與田塊直接連接。橫向生產(chǎn)路可間隔100～300m布置一條,縱向生長路可間隔200～500m布置一條；與紫色巖溶區(qū)相比,石灰?guī)r溶區(qū)的地質(zhì)條件更具有復(fù)雜性,應(yīng)繞避溶蝕洼地、溶洞發(fā)育區(qū)和大斷層破碎帶。農(nóng)村道路應(yīng)盡可能地結(jié)合地形地貌條件及生產(chǎn)方式進行布置,體現(xiàn)因地制宜原則。田間道可與支、斗渠溝結(jié)合布置,生產(chǎn)路可與農(nóng)渠溝結(jié)合布置。因此,西南丘陵山區(qū)農(nóng)村道路布局不僅要充分考慮農(nóng)村居民點分布、農(nóng)田水利設(shè)施和耕作田塊設(shè)置等,還應(yīng)順應(yīng)自然環(huán)境條件、融于農(nóng)業(yè)自然人文景觀。(2)農(nóng)村道路工程設(shè)計紫色巖區(qū)路面設(shè)計高出原地面約20～30cm,路面墊層采用20cm厚手擺片石,路面基層為10～15cm泥結(jié)碎石穩(wěn)定層,路面面層采用15～20cm厚C25～C30水泥混凝土進行鋪設(shè)。該區(qū)域土基強度較高,可采用原土路基夯實,壓實度在90%以上。路基的寬度為4.5～5.0m,邊坡采用1：1.5。同時考慮到本區(qū)域降雨期較長,集雨面積較大,可在路基來水一側(cè)布設(shè)邊溝,溝底寬0.25～0.30m、凈深0.3～0.4m,溝壁采用M10～M15水泥砂漿砌毛條石或漿砌塊石,溝底鋪設(shè)8～10cm厚C15～C20水泥混凝土。為了保證路基的穩(wěn)定,設(shè)計在田間道的另一側(cè)利用條石修建條石路肩、預(yù)制混凝土或土質(zhì)路肩；石灰?guī)r溶地區(qū)常常遭受兩側(cè)山坡水土的沖蝕,三水轉(zhuǎn)化快,因此,路基和路面設(shè)計比紫色土區(qū)厚,高出原地面約30～40cm。路面墊層采用20cm厚手擺片石,路面基層為15cm泥結(jié)碎石穩(wěn)定層,路面面層采用18～20cm厚C30水泥混凝土進行鋪設(shè)。路面寬度凈寬為3.5～4.5m,橫坡為0.3%～0.5%；田間道的平曲線半徑(轉(zhuǎn)彎半徑)應(yīng)不小于15m,特殊困難地段不得小于10m,平曲線長度不得少于15m。當平曲線半徑等于或小于150m時,應(yīng)在曲線上設(shè)置超高,在曲線內(nèi)側(cè)加寬,并在平曲線兩端各設(shè)置一段不少于10m的超高緩和段,超高橫坡度最大值不超過8%,積雪冰凍地區(qū)不超過6%。田間道最大縱坡宜取6%～8%,特殊情況下,丘陵地區(qū)不宜大于11%,山區(qū)不宜大于13%；在海拔2000m以上或嚴寒冰凍地區(qū)不宜大于8%。無論是紫色巖區(qū)還是石灰?guī)r溶區(qū),當田間道路面寬度小于4.0m時,均應(yīng)在適當距離內(nèi)設(shè)置錯車道。錯車道應(yīng)設(shè)在有利地點,并使駕駛員能看到相鄰兩錯車道間駛來的車輛。設(shè)置錯車道路段的路面寬度不應(yīng)小于6.5m,間隔宜為300～600m,有效長度宜為15～25m；紫色巖區(qū)生產(chǎn)路宜采用片石、塊石墊層,路基寬宜為0.6～2.7m,路面寬度設(shè)計為0.6～2.5m。無積水和流水沖刷的地區(qū)可采用夯實素土路基,生產(chǎn)路路基宜高于路面0.1～0.2m。石灰?guī)r溶區(qū)宜采用漿砌石質(zhì)路基,高出田面高程0.2～0.5m。生產(chǎn)路路面均可采用砼現(xiàn)澆、預(yù)制砼板、青石板等材料,砼路面厚度宜為5～20cm,預(yù)制砼板、石板宜為6～15cm,其他材料宜為8～20cm。田間道、生產(chǎn)路跨越溝渠或溪溝處可布置農(nóng)橋,農(nóng)橋分為田間道橋和人行便橋。結(jié)構(gòu)設(shè)計安全等級不低于三級。農(nóng)橋的結(jié)構(gòu)形式可采用梁式和拱式。建筑材料可用磚、石、混凝土及鋼筋混凝土等。道路穿越渠道時,宜在渠、路下或地下設(shè)置涵洞。涵洞的頂端距路基要有一定的距離為20～30cm。涵洞水流的方向,應(yīng)與洞頂填方溝渠或道路正交,與原水道的方向一致。涵洞的形式可采用圓形、箱形、蓋板式和拱式等,選用混凝土或鋼筋混凝土管。因此,西南丘陵山區(qū)農(nóng)村道路工程設(shè)計,除充分考慮道路所經(jīng)路段的地質(zhì)地貌、水文、土地利用類型和土壤特性外,還應(yīng)就地取材,降低建造成本。(3)農(nóng)村道路體系網(wǎng)絡(luò)特征五個樣區(qū)自然條件與社會經(jīng)濟等差異加劇了區(qū)域各級道路體系構(gòu)建重點的差異,但整體上道路體系均更加趨于健全和完善,網(wǎng)絡(luò)特征存在一定差異但有所縮小。從廊道指數(shù)來看,五個樣區(qū)農(nóng)村道路建設(shè)后較建設(shè)前的總長度、密度均有不同程度增加。建設(shè)前,各行政村道路總長度變化范圍為6.73km～76.36 km,相差11.4倍,建設(shè)后其為7.88km～82.15km,變化范圍縮小至10.4倍；建設(shè)前,道路網(wǎng)絡(luò)密度為38.18 m/hm2～149.6 m/hm2,相差近4倍,建設(shè)后其為65.87 m/hm2～159.6 m/hm2,相差僅2.4倍。此外,五個樣區(qū)農(nóng)村道路建設(shè)前后道路類型組合的結(jié)構(gòu)變化也較為明顯,整體上,田間道比例提高幅度較大,但生產(chǎn)路在整個道路體系中所占的比例仍最大,其次為田間道,等級公路最少。建設(shè)前,樣區(qū)Ⅰ、樣區(qū)Ⅱ、樣區(qū)Ⅲ、樣區(qū)Ⅳ、樣區(qū)Ⅴ的等級公路：田間道：生產(chǎn)路的比例依次分別為11：15：74,0：31：69,9：12：79,3：17：80,8：28：64。建設(shè)后,樣區(qū)Ⅰ、樣區(qū)Ⅱ、樣區(qū)Ⅲ、樣區(qū)Ⅳ、樣區(qū)Ⅴ的等級公路：田間道：生產(chǎn)路的比例依次分別為9：17：74,0：27：73,7：23：70,3：16：81,6：25：69。從農(nóng)村道路網(wǎng)絡(luò)指數(shù)來看,網(wǎng)絡(luò)密度d指數(shù)、網(wǎng)絡(luò)閉合度α指數(shù)、線點率β指數(shù)以及網(wǎng)絡(luò)連接度γ指數(shù)均有所提高,而成本比C指數(shù)則有一定程度降低。建設(shè)前,網(wǎng)絡(luò)閉合度α指數(shù)變化范圍為0.126～0.361,線點率β指數(shù)變化范圍為1.242～1.681,連接度γ指數(shù)變化范圍為0.419～0.577,成本比C指數(shù)變化范圍為0.9908～0.9971；建設(shè)后,道路網(wǎng)絡(luò)的α指數(shù)變化范圍為0.312～0.370,β指數(shù)變化范圍為1.614～1.707,γ指數(shù)變化范圍為0.542～0.582,C指數(shù)變化范圍為0.9913～0.9956。同時,在西南丘陵山區(qū),隨著道路的擴展,道路網(wǎng)絡(luò)的節(jié)點數(shù)和廊道數(shù)也呈增加趨勢,這種增加為直線關(guān)系,而且不同區(qū)域節(jié)點數(shù)和廊道數(shù)差異較大,造成區(qū)域之間道路密度存在一定差異。此外,道路密度與網(wǎng)絡(luò)閉合度α指數(shù)、線點率β指數(shù)、網(wǎng)絡(luò)連接度γ指數(shù)呈正相關(guān)關(guān)系,而與C指數(shù)呈顯著負相關(guān),即隨著道路網(wǎng)絡(luò)的擴展,成本比逐漸降低。Moran指數(shù)進一步表明：建設(shè)前,樣區(qū)Ⅴ的道路密度較分散,而樣區(qū)Ⅰ、Ⅱ、Ⅲ和Ⅳ均是相對聚集,建設(shè)后,樣區(qū)Ⅰ、Ⅲ和Ⅴ道路密度顯著增加,而樣區(qū)Ⅱ和Ⅳ道路密度增加的幅度不大,造成這種差異的原因在于樣區(qū)Ⅱ和Ⅳ地形相對陡峭,而樣區(qū)Ⅰ、Ⅲ和Ⅴ的地勢相對較平坦。因此,農(nóng)村道路作為一個農(nóng)村景觀廊道或農(nóng)田物質(zhì)流、價值流通道,可用網(wǎng)絡(luò)結(jié)構(gòu)分析進行表達(評價),并實現(xiàn)農(nóng)村道路體系網(wǎng)絡(luò)優(yōu)化。(4)農(nóng)村道路體系景觀效應(yīng)在類型水平上,農(nóng)村道路對周邊土地利用格局的干擾程度以道路為中心線,向兩側(cè)大致呈現(xiàn)逐漸衰減的變化規(guī)律。田間道主要穿過水田、早地及居民點人類活動最頻繁的區(qū)域,對三者的破碎化干擾最顯著。田間道25m以內(nèi)對景觀連接度干擾最明顯,25m以外干擾度逐漸衰弱。田間道10m以內(nèi)對土地利用干擾強度最劇烈,10-25m以內(nèi)干擾強度較為劇烈,25m以外隨著距離的增加,干擾程度逐漸衰減。0-25m干擾帶內(nèi)田間道對土地利用類型的分割破碎程度大致呈現(xiàn)此規(guī)律：早地>水田>居民點>水域>林地。25m-250m干擾帶內(nèi),水田>旱地>居民點>水域>林地。生產(chǎn)路2.5m以內(nèi)對土地利用格局干擾強度隨距離增加反而增強,2.5-10m以內(nèi)干擾強度隨距離增加減小且干擾最劇烈,10-30m以內(nèi)干擾強度相當,30m以外隨著距離的增加,干擾程度逐漸衰減。0-20m干擾帶內(nèi)生產(chǎn)路對土地利用類型的分割破碎程度大致呈現(xiàn)此規(guī)律：水田>旱地>居民點>水域>林地。20m-120m干擾帶內(nèi),旱地>水田>居民點>水域>林地。在景觀水平上,田間道對周邊土地利用景觀格局的干擾程度基本也以田間道為中心線,向兩側(cè)大致呈現(xiàn)逐漸衰減的變化規(guī)律,但生產(chǎn)路向兩側(cè)大致呈現(xiàn)先增強再逐漸衰減的變化規(guī)律。田間道5m以內(nèi)對土地利用景觀干擾強度最強,5m以外隨著距離的增加,干擾程度逐漸衰減乃至不明顯。田間道建設(shè)后,除樣區(qū)Ⅳ在0～10m內(nèi)景觀破碎情況略有加劇外,其他四個樣區(qū)在10～250m內(nèi)基本不變,在0～10m內(nèi)基本得到改善或緩解；景觀邊界的復(fù)雜彎曲程度在一定程度上均略有提高,類型景觀形狀規(guī)則化程度有所增加,樣區(qū)優(yōu)勢土地利用景觀類型相鄰斑塊的連續(xù)性總體上有所提高,主要土地利用景觀類型優(yōu)勢地位未受威脅甚至有所提高。生產(chǎn)路5m以內(nèi)對土地利用景觀干擾強度隨距離增加而增強,2.5～5m以內(nèi)干擾強度隨距離增加干擾最為劇烈,5～10m以內(nèi)干擾強度較大,10～30m以外隨著距離的增加,干擾程度逐漸衰減乃至不明顯。生產(chǎn)路建設(shè)后,景觀破碎度在0～30m內(nèi)得到改善,在30～120m內(nèi)基本不變外,但其景觀邊界的復(fù)雜彎曲程度在一定程度上略有提高,類型景觀形狀規(guī)則化程度稍有降低。因此,農(nóng)村道路作為一種土地利用(景觀)類型,它的重建能優(yōu)化農(nóng)村局地土地利用(景觀)格局,實現(xiàn)土地高效利用。綜上所述,本文主要以生產(chǎn)路、田間道的布局與結(jié)構(gòu)設(shè)計闡明了西南丘陵山區(qū)農(nóng)村道路等級結(jié)構(gòu)體系的構(gòu)建思路；從廊道結(jié)構(gòu)指數(shù)、網(wǎng)絡(luò)結(jié)構(gòu)指數(shù)、空間自相關(guān)Moran指數(shù)三個層面分析了西南丘陵山區(qū)農(nóng)村道路體系構(gòu)建前后的網(wǎng)絡(luò)特征；在這兩者的基礎(chǔ)上探討了農(nóng)村道路的形成和發(fā)展對周邊土地利用格局的影響,從而揭示了西南丘陵山區(qū)農(nóng)村道路體系構(gòu)建前后的景觀效應(yīng)。但事實上道路的景觀效應(yīng)不僅體現(xiàn)在道路對周邊土地利用的影響,還包括對區(qū)域交通、人類活動、社區(qū)結(jié)構(gòu)和組織、生態(tài)系統(tǒng)及功能演替等的影響,而且這種效應(yīng)在道路構(gòu)建的整個過程中都發(fā)生著作用。因此,需從多角度加強農(nóng)村道路體系構(gòu)建過程中人類活動、社區(qū)結(jié)構(gòu)和組織、社會經(jīng)濟發(fā)展的動態(tài)研究。

    As one of the key rural infrastructure, rural roads has got rapid expansion recently basing on the comprehensive land consolidation, the new countryside construction and urban and rural harmonious development. Current researches focus on high-grade road system in the large geomorphic unit, like the gathering and radiation of logistics and the exchange of information coming from coherent road network such as highways, railways, state (province) road or county road, and "channel - blocking " effect driving on heterogeneity and diversity of landscape use and land cover in large geomorphic unit and its impact on ecosystems. Low-grade rural roads are concentrated in the layout and evaluation of road network, design and cost control of road construction, engineering construction, quality control and maintenance management, surface drainage, slope erosion and road erosion control and so on. However, the rural roads distributed widely in the Hilly-mountainous Region of Southwestern China are restricted not only by human economic activities, but also by natural conditions. Its construction and operation provide a protection for social development and a promoting economic development, while cause a division, disturbance, destruction and degradation of natural landscape and ecosystems and so on. Considering this, picking 14 administrative villages from Sichuan Province(areaⅠ), Guizhou Province(areaⅡ) and Chongqing City(areaⅢ,ⅣandⅤ) as 5 study areas, this paper analyzed the type and function of rural roads in different geographical environment combining with socio-economic levels including topography, hydrogeology, climate, soil, vegetation, rural population, cultivated land, per capita arable land, infrastructure, agricultural production conditions, farming systems and the socio-economic.It also cleared the requirement for rural roads according to the economic development status and future development trend in the Hilly-mountainous Region of Southwestern China. And it researched the engineering technology of rural roads such as surface and subgrade combining with the usage of local agricultural machinery and characteristics of common building materials. Moreover, it built the rural road system in Hilly-mountainous Region of Southwestern, and analyzed features of the rural road network systems and its landscape effect so that provided a support on theory and technical to rural road system layout and design in Hilly-mountainous Region of Southwestern China.(1) The layout of rural roadRural roads can be divided into field roads and production roads by function and road pavement width. Field road is a road contacting rural residential area with piece of paddy fields, which mainly services for cargo transporting, transferring of operating machinery to field and fueling the machine, adding water, adding seed and other production operation. It is better to adopt orthogonal when field road intersect to facilitate turning of farm machinery. Field roads should be laid along the short edge of the piece of paddy field, whereas it can be laid in the middle of field operation area in the dry farming region, along the long side of the piece of paddy field so that farm machinery can enter the work area on both sides to reduce the blank line. It should be arranged according to specific terrain in the terrace area shall, laid by the method of walking along the edge of the trench. Field road is usually set beside the gutter, deep in ditch or on the mountain ridge. It presents a bias shape when the mountains are low and slopes are even; it presents an "S" shape or a spiral shape winding up the mountain when the mountains are high and slopes are steep. Production road is the kind of road to link each piece of paddy fields for field production operations and mainly services for manual field work and harvesting agricultural products. It should be criss-cross laid to form a network with field road. It often locates in the long side of the piece of paddy field and presents different ways in dry lands and paddy fields. One horizontal production road in dry lands farmland separates another from 40 to 200 meters. It can be laid combining with gallet bank in areas gallet is widely spread to save space. Vertical production roads are often arranged on the hilly ridges and one separates another from 200 to 500 meters according to the length of the field surface. If the production roads and ditches are not conducive to drain off water or traffic when combined settings, they will be arranged separately. Production roads in paddy can be set outside the agricultural ditch and directly connected with paddy fields. Horizontal production road can be arranged an interval of 100 to 300m, vertical one can be arranged an interval of 200 to 500m; It should avoid areas like erosion around the depressions, cave development zones and large fault fracture zone in soluble limestone regimen which with complex geological conditions. Rural roads should be laid combining topography conditions and production methods as far as possible. What is more, field roads can be laid combining branch canal and lateral canal, production roads can be laid with field ditch. In sum, the layout rural roads in the Hilly-mountainous Region of Southwestern China should not only consider the distribution of rural settlements, facilities of irrigation and settings of farming plots, but also harmonize with the natural environmental conditions, agricultural and human landscape.(2) Engineering design of rural roadsRural road surface is designed above the original ground surface about 20 to 30cm in purple rock area, and the pavement bed course is built by hand placed stones of 20cm. The foundation course is a stable layer of gravel mud of 10 to 15cm, and road surface is covered by 15 to 20cm thick cement concrete of C25～C30. The soil base in this area has a high intensity so the subgrade can be compacted directly with a degree of compaction above 90%. The width of subgrade is 4.5 to 5.0m, slope ratio is 1:1.5. Taking into account the long rainfall period and large rainwater harvesting area in the region, the ditch can be laid at the runoff side of the subgrade, the width of it is 0.25 to 0.30m, and the net depth of it is 0.3 to 0.4m. The trench wall of it is built by cement mortar boulder strip of M10-M15 or mortar block stone, and the bottom is paved by cement concrete of C15-C20 with 8～10cm. To ensure the stability of the subgrade, the road shoulder is adopted on the other side of the field road using stone curb, precast concrete or soil; Due to the frequent water and soil erosion from both sides of the hill in the soluble limestone region, the subgrade and pavement in this region are designed thicker than the purple soil region, and exceed the ground of 30 to 40cm. The pavement bed course is built by hand placed stones of 20cm, and the foundation course is a stable layer of gravel mud of 15cm, and road surface is covered by 18 to 20cm thick cement concrete of C30. Clear width of the road is 3.5 to 4.5m with cross slope of 0.3% to 0.5%. The flat curve of field road has a radius (turning radius) not less than 15m, on special difficulties not less than 10m, and its length cannot be less than 15m. When the radius of flat curve is equal to or less than 150m, the curve should be set ultra-high and the inside of the curve should be widened. Meantime the ultra-high eased segment not less than 10m should be set at both ends of a flat curve. The ultra-high cross slope value does not exceed 8% and not more than 6% in snow frozen area. The maximum longitudinal slope of field road should take 6% to 8%. Under special circumstances, it’s not more than 11% in hilly area, not more than 13% in the mountain area, and not more than 8% in an altitude of 2000m above areas or freezing cold region. Whether in purple rock area or soluble limestone area, the passing bay should be set in the appropriate distance when the road surface width of field road is less than 4.0m, Passing bay should be located in vantage point, and make the driver can see the approaching vehicles from two adjacent passing bay. The section of pavement setting the passing bay has a road surface width of not less than 6.5m, the interval should be of 300 to 600m, the effective length shall be 15 to 25m; Production road in purple rock area should adopt rubble, stone block cushion, and its subgrade width should be 0.6 to 2.7 m. The width of the road is designed from 0.6 to 2.5m. Soil can be used to compact subgrade in free water and erosion areas, and the subgrade of production road should be higher than the road surface 0.1 to 0.2m. The grouting stone subgrade should be adopted in soluble limestone area, above the field surface 0.2 to 0.5m. The pavement of production road can be produced by cast-in-situ concrete, precast concrete board, green flag and other materials. The concrete road surface should be of 5 to 20cm thick, the precast concrete board and flag should be of 6～15cm, and other materials are desirable of 8～20cm. Agricultural bridge can be arranged where field road and production road crossing ditches or gully which falls into for field road and for pedestrian. Its structural design safety level is not less than the third grade. Types of agriculture bridges can be the beam type and the vault type, and building materials usually are brick, stone, concrete and reinforced concrete etc. Culvert should be built under the canal, road or the ground when the road crossing the canal. There should be a certain distance of 20 to 30cm away from the top of the culvert to the subgrade. Culvert water direction should be orthogonal with fill ditches on roof or roads, in accordance with the original direction. The culvert can be made by concrete or reinforced concrete pipe, and the form of it can be round, box, cover type and vault type etc. In a word, the engineering design of rural roads in Hilly-mountainous Region of Southwestern China should consider the geological topography, hydrology, land use and soil characteristics of the road sections passing, meanwhile make use of local materials to reduce costs.(3) Characteristics of the rural road network systemOn the one hand, the differences of natural conditions and socio-economic in these study areas intensified the differences of focus on building in regional road system. On the other hand, the whole road systems had become more comprehensive, and the differences in the network characteristics had narrowed. Like the index of view from the corridor, the total length and density of rural roads in all cease areas had increased. Before building, total length of the road in these villages ranged from 6.73km to 76.36 km, the longest was 11.4 times longer than the shortest. The network density of road ranged from 38.18 m/hm2 to 149.6 m/hm2, and the biggest was 11.4 times bigger than the smallest. After building, the length ranged from 7.88 km to 82.15 km and the gap narrowed to 10.4 times; the density ranged from 65.87 m/hm2 to 159.6 m/hm2 and the gap was only 2.4 times. In addition, there was a remarkable structural change in the type of road consisting systems. Although increased greatly the proportion of field road, the production of road still occupied the main parts in the entire road system. Before building, the ratio of high road, Field Road and production ratio in areaⅠ, areaⅡ, areaⅢ, areaⅣ, areaⅤwere 11:15:74,0:31:69,9:12:79,3:17: 80,8:28:64 respectively. After building, those were 9:17:74,0:27:73,7:23:70,3: 16:81,6:25:69.Considering the index of the rural road network, the network density index (d), the network closure index (α), the line point rate (β) and the network connectivity index (γ) were higher, while costs rate index (C) reduced in some extent. Before building, a ranged from 0.126 to 0.361:βranged from 1.242 to 1.681:y ranged from 0.419 to 0.577:C ranged from 0.9908 to 0.9971. After building, a index ranged from 0.312 to 0.370, (3 index ranged from 1.614 to 1.707, y index ranged from 0.542 to 0.582, C ranged from 0.9913 to 0.9956.Meanwhile, in the Hilly-mountainous Region of Southwestern, there were an increasing trend in the number of nodes and corridors of the road network with the road expansion. The differences of road density in these regions were attributed to the differences of the number of nodes and corridors between the different regions. In addition, a, (3, y were positively correlated whereas were significantly negatively correlated with C, that is, the cost ratio decreased with the expansion of road network. Moran index further indicated that:before the construction, the road density inⅤwas decentralized, whereas they were relatively gathered inⅠ,Ⅱ,ⅢandⅣ. After the construction, the road density inⅠ,ⅢandⅤincreased significantly, while they increased slightly inⅡandⅣ. The reason for this is that the terrain ofⅡandⅥis relatively steep, while it is relatively flat inⅠ,ⅢandⅤ. So we found that:as a rural agricultural landscape corridor or channel for material flow and value flow, the rural roads can be evaluated by the network structure analysis, moreover by it can attain the rural road system network optimization.(4) The landscape effect of rural road systemAccording the type, using the road as centerline, the degree of interference of rural roads on the surrounding land use pattern generally shows a gradual decay to both sides of the road. Across the paddy field, dry land and the regions which are the human settlements in, the field road make the most significant interference with the fragmentation of those regions. The results indicated:it made the most significant degree of interference with landscape connectivity within 25m, and the interference gradually weakened beyond 25m. Meantime, it brought severe interference with land use disturbance in 10-25m and the hugest one was within 10m. Exceeding 25m, the degree of interference gradually decayed away as the distance increased. In 0-25m interference band, degree of fragmentation of the land-use types from field road showed:dry land> paddy> settlement water> woodland, and in 25m-250m band showed:paddy field> dry> settlement> water> woodland. The intensity of interference pattern of land use from production path increased with distance adding within 2.5m, while it decreased with distance adding and the severest disturbance happened within 2.5-10m. It changed less in 10-30m and gradual decayed over 30m. In 0-20m interference band, degree of fragmentation of the land-use types from production road showed:paddy fields> dry> settlement> water> woodland, and in 25m-250m band showed:dry land> paddy> settlement> water> woodland.According the landscape, using the road as centerline, the degree of interference of field roads on the surrounding landscape pattern also shows a gradual decay to both sides of the road, while interference of the production shows an increasing trend at first and then gradually decayed. The results indicated:the strongest intensity of disturbance on land use landscape from field road was in 5m, and it decreased with distance increasing beyond 5m. After the construction of field road, except IV which had a slightly increased of landscape fragmentation in the 0-10m, the landscape fragmentation in other four regions were improved or mitigated, they were almost same in the 10-250m. The complex bending degree of landscape border raised slight in a certain extent, and the degree of regular shape of the landscape types increased. The continuity of adjacent plots of preponderant land use in study areas increased overall, and the dominant landscape types was not threatened or even increased. The disturbance on landscape from production road increased with distance adding within 5 m, and the most severe of interference came from 2.5 to 5m band. In the 5-10m band, the disturbance was still large. Over 10m, however, the degree of interference gradually decayed away as the distance increased. The degree of the landscape fragmentation within the 0-30m was improved due to the construction of production road. Although it kept same within 30-120m, the complexity of landscape boundaries rose slightly while the degree of regular shape of the landscape types reduced slightly. Therefore, as a landscape type, the rural roads can optimize the reconstruction of local rural land use so that the efficient use can be achieved.In summary, this paper demonstrated the idea about the hierarchy system of rural roads in Hilly-mountainous Region of Southwestern China by the layout and the structural design of production road and field road. It analyzed features of the network system of rural road in Hilly-mountainous Region of Southwestern China pre and post construction by indexes of corridor structure, network structure and the spatial autocorrelation (Moran). Basing on those, it discussed what influence on the surrounding land use pattern from the formation and development of rural roads. Thus it revealed the landscape effect pre and post construction of the rural road system in Hilly-mountainous Region of Southwestern. However, the landscape effect from road is not just in the impact on the surrounding land use, it also includes impact on regional transportation, human activity, community structure and organization and function and succession of ecosystems and so on. What is more, this effect works in the whole process of road building. Therefore, it is necessary to strengthen the research on human activity, community structure and organization, the dynamics of social and economic development which correlate with construction process of rural road system from multi-angle.

西南丘陵山區(qū)農(nóng)村道路構(gòu)建及其景觀效應(yīng)

摘要7-11Abstract11-15第1章 文獻綜述16-22    1.1 道路網(wǎng)絡(luò)16-17    1.2. 道路設(shè)計17-19    1.3 道路景觀19-20    1.4 結(jié)語20-22第2章 緒論22-26    2.1 研究背景及意義22-23    2.2 研究目標23    2.3 研究內(nèi)容23-24    2.4 技術(shù)路線24-26第3章 樣區(qū)概況26-42    3.1 樣區(qū)空間分布26-27    3.2 樣區(qū)自然條件27-34        3.2.1 氣候、地質(zhì)、土壤27-30        3.2.2 地貌形態(tài)類型30-34        3.2.3 巖石理化性質(zhì)34    3.3 樣區(qū)社會經(jīng)濟條件34-42        3.3.1 人口資源狀況34-35        3.3.2 經(jīng)濟發(fā)展水平35        3.3.3 農(nóng)業(yè)機械水平35-42第4章 農(nóng)村道路體系布局與結(jié)構(gòu)設(shè)計42-66    4.1 數(shù)據(jù)處理與方法42-48        4.1.1 數(shù)據(jù)預(yù)處理42-45        4.1.2 農(nóng)村道路體系構(gòu)建思路45-48    4.2 結(jié)果與分析48-64        4.2.1 農(nóng)村道路體系布局設(shè)計48-51        4.2.2 農(nóng)村道路體系結(jié)構(gòu)設(shè)計51-59        4.2.3 農(nóng)村道路體系橫斷面設(shè)計59-64    4.3 結(jié)語與討論64-66第5章 農(nóng)村道路體系構(gòu)建的網(wǎng)絡(luò)效應(yīng)66-76    5.1 數(shù)據(jù)處理與方法66-68        5.1.1 數(shù)據(jù)預(yù)處理66        5.1.2 道路廊道數(shù)量特征分析66-67        5.1.3 道路網(wǎng)絡(luò)結(jié)構(gòu)效率分析67        5.1.4 道路網(wǎng)絡(luò)空間自相關(guān)分析67-68    5.2 結(jié)果與分析68-73        5.2.1 農(nóng)村道路體系的數(shù)量特征68-69        5.2.2 農(nóng)村道路體系的質(zhì)量特征69-72        5.2.3 農(nóng)村道路體系的網(wǎng)絡(luò)特征72-73        5.2.4 農(nóng)村道路體系空間自相關(guān)性73    5.3 結(jié)語與討論73-76第6章 農(nóng)村道路體系構(gòu)建的景觀效應(yīng)76-110    6.1 數(shù)據(jù)處理與方法76-81        6.1.1 數(shù)據(jù)預(yù)處理76-77        6.1.2 緩沖區(qū)構(gòu)建77        6.1.3 景觀格局指數(shù)77-81        6.1.4 數(shù)數(shù)據(jù)歸一化處理81    6.2 結(jié)果與分析81-108        6.2.1 等級公路對土地利用格局的干擾效應(yīng)81-85        6.2.2 田間道對土地利用格局的干擾效應(yīng)85-97        6.2.3 生產(chǎn)路對土地利用格局的干擾效應(yīng)97-108    6.3 結(jié)語與討論108-110第7章 結(jié)論與展望110-116    7.1 結(jié)論110-113        (1) 農(nóng)村道路體系的布局設(shè)計110-111        (2) 農(nóng)村道路體系的結(jié)構(gòu)設(shè)計111        (3) 農(nóng)村道路體系的網(wǎng)絡(luò)特征111-112        (4) 農(nóng)村道路體系的景觀效應(yīng)112-113    7.2 研究特色與創(chuàng)新點113-114    7.3 研究展望114-116參考文獻116-122致謝122-124攻讀博士學(xué)位期間發(fā)表的論文和參與的課題124

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