On Pattern Of Rural Road And Its Design In Hilly-mountainous Region In Chongqing

The current road system in the hilly-mountainous region of Chongqing were characterized by the low-level of agricultural mechanization, the undeveloped complemented rural road designing technology, the poor overall structure of roads and low construction standards of rural roads, which could not meet the requirements of the agricultural mechanization in modern society. Thus it has become a focus that how to improve established rural road pattern and system in soil project, in order to facilitate local agricultural production. The optimization of rural road pattern and structural design were one of the most effective ways improving the road structure and standards, to raise the level of agricultural mechanization and achieve the goal of socialist new countryside. Roads' research on at home and abroad mainly concentrated on highway construction and its complemented projects, such as geotechnical engineering on the foundation of stability, slope stability, seepage stability and so on. The study of rural road system was only to be found in the research on land consolidation, land cover change and so on. What's more, the designing of rural roads mostly belonged to township planning and designing. So the research of rural road construction standards was comparatively lack, especially in the hilly region of Chongqing.Taking Dashi Town in Hechuan and Bashan Town in Zhong County as case studies, the paper conducted a research of the road pattern and its designing system using different methods, considering the impacting factor of the topography, geology, settlements, and field distribution in hilly area. The similarities and differences were compared among the two areas with various terrain features in terms of the road pattern and designing system. The results could be helpful for road designing in hilly area, and also gave a worthy reference to the construction of low-level road in Southwest China1 The evaluation of agricultural machinery and rural road in the hilly region of ChongqingOn the basis of investigating the conditions of agricultural machinery and analysis on the type of agricultural machinery and the corresponding parameters, the frequency of the agricultural machinery load was calculated by Load Fatigue theory, which would provide the foundation for pavement design. At the same time, the conditions of the rural roads at region were studied. and the physical properties of soil which include soil texture and liquid and plastic limits were measured. And the damage froms of subgrade were discussed. on the basis of the results. At last, it is generally discussed that the quality level was bad or good which bases on calculating and evaluating tit by the assignment method.Selecting the type of LJ2010PD four-wheel farm vehicles as the main access machinery of the field roads at the busy season, the standard axle loads was 145 times per day and the cumulative effect number of standard axle load was 1,128,200, which demonstrates that the conditions of agricultural machinery of the rural roads had the characteristics of seasonal and lighter axle load.The width of the rural road includes five grades(2～3m,3～4m,3～4m,5～6m and 6～7m). The largest proportion of the rural roads grade was within 2～3m in Dashi town, Hechuan county of Chongqing which was 38.22%, and the proportion had a decreasing trend with increasing on the width grade. The minimum ratio was 4.83% and the corresponding level of the range was 5～6m. The largest proportion was within 3～4m at in Bashan town, Zhong county Chongqing which was 50.15%, and the minimum ratio appears on the level of 6～7m, which is 3.53%. It is concluded that the rural road condition was not reasonable at study area, the width was chaotic, and there was no uniform building standard. The comprehensive quality level of the roads was 1.63 and 1.24 respectively, which indicated that the grade quality value of the roads was low and the road was still in the stage of low-quality levels and grades.2 Pattern and optimization of rural roads in the hilly region of ChongqingFive indicators (density of road network, detour, connectivity and the proportion of connected residential points and field) were selected and the pattern of rural road was further optimized according to the results.The result of density of road network was 12.17m/hm² in Dashi town, Hechuan county of Chongqing and the result of density of road network was 15.67m/hm² in Bashan town, Zhong county Chongqing. The connectivity was 1.26 and 1.86. Generally speaking, the overall level was bad at the density of road network, number and structure. The connectivity proportion of residential points and fields were low and the distributing of field road had a strong influence in the residential points. From what has been discussed above, it was concluded that the pattern of field was so worse that it could not keep pace with the development of agriculture. So the number and structure of road should be further optimized. The level value of detour was located between 1～1.2 and 1.2～1.4 and the route of the field road was reasonable. So it could provide a good reference in the pattern optimization with it.The density and connectivity of footway network was also small as field road. The affect of residential points was the same as the field road. The connected proportion between residential points and fields has a close relationship with the number of footway. The way of optimized was closely connected with factors of field and residential points. The level value of detour was located between 1-1.2 and 1.2-1.4 and the route of the field road was reasonable. So it provide d a good reference to the pattern optimization with it.3 Design of rural roads in the hilly region of ChongqingAccording to the problem of subgrade and pavement road, the soil power and road project were applicated. and the structure of sub grade and pavement road were optimized according to the pavement fatigue load theory, at the same time, the quality of road were evaluated on the basis of the results of calculation.The slope angle of subgrade was one of the most important factors causing the stability of it. The critical of the slope angle was 32.5°and the ratio was 1:1.6. The pavement load and temperature fatigue stress were the most important factors influencing the pavement thickness. If Cement Concrete thickness was 0.18m, the pavement load fatigue stress (σ_pr)was 3.75 and the temperature fatigue stressσ_tr was 0.32. r_r(σ_pr+σ_tr) was 4.36, which was under the flexural tensile strength. If Cement Concrete thickness was 0.16m, the pavement load fatigue stress(σ_pr) was 4.42 and the temperature fatigue stress(σ_tr) was 0.12. r_r(σ_pr+σ_tr) was 4.39,which was beyond the flexural tensile strength. So it is concluded that the least thickness of Cement Concrete is 0.18m, and the maximum of it is 0.22m. Cement stabilized aggregate which is 0.18m was generally used as the base material of road and rubble which is 0.20m was generally used as the cushion material of road. The road structure could bear the comprehensive action from the pavement load and temperature fatigue stress. The pavement thickness of footway was 6-12cm and the material of was cast-in-place concrete, which could meet the need of local agricultural production.From what has been discussed above, the pattern and design system were studied and made up the weakness of research on rural road. It did not always focus on the research of highway and high-grade road any more. Thus the optimization of pattern and design system was made on rural roads in the hilly region of Chongqing. Five indicators (density of road network, detour, connectivity and the proportion of connected residential points and field) were selected and the internal structure of rural road was analyzed in the paper. But the results of statistics would become different as the change of economic and policy in the area. Therefore, the dynamic pattern change of rural road network should be further studied in future.