道桥专业外文翻译--沥青路面结构设计的低成本农村道路(编辑修改稿)

道桥专业外文翻译--沥青路面结构设计的低成本农村道路(编辑修改稿)内容摘要：

change of modulus of the roadbed. The increase in the modulus of roadbase or subbase is also effective to decrease the deflection of the road surface. On the other hand， the deflection of the road surface decreases gradually when the modulus of the surface increases， being the least effective factor. When the modulus of the road surface increases to a certain value， decrease in road surface deflection is not apparent. Fig. 2 shows the effect of the modulus of each layer on road surface deflection. From the above discussion， we conclude that the most sensitive layer for road surface deflection is subbase， and the next is roadbase. To decrease the road surface deflection of lowcost rural roads， the 5 strength and stability of the roadbed should be enhanced, and the materials with a certain thickness and relatively high density should be used to pave the subbase. The traffic volume or the accumulative equivalent axle load action times(frequency)within the designed life of road is used to determine the type and thickness of the asphalt pavement road surface, and the results are listed in Table 8，where veh/d means the number of the equivalent the passenger cars per day. For a low traffic volume rural road with Ne 500 000， graded broken stones(or gravel)can be used as a flexible base. The flexible base has good strength and effectively prevents reflection cracks of the asphalt pavement road surface, provided the graded broken stones(or gravel ) meets the requirements for high density(degree of paction ,100%. To ensure the sufficient strength and stability of the flexible base， its thickness is not less than 15 cm， the thickness of the aggregate subbase is not less than 20 cm， A semirigid base usually has a good bearing capacity For the rural roads with Ne)500 000， or those with low traffic volumes but relatively,the minimum thickness of semirigid base or subbase is 1618 cm 5 Calculation of the Thickness of Road Surface Deflection (1)Road surface deflection Road surface deflection is a vertical distortion caused by vertical load on the road surface. It not only reflects the whole strength and stiffness of asphalt pavement structure and roadbed， but also has a close internal relation with the service condition of the pavement. (2)Design deflection The design deflection is the index representing the stiffness of the pavement structure. It is also the deflection of the pavement which is established according to the accumulative equivalent axle load estimated to pass over a lane in the expected design life, road types, road classification， and the types of road surface and roadbase. The design deflection is not only the main basis for the design thickness of the pavement structure， but also the necessary index for the examination and acceptance of the project. Through theoretical analysis and experimental study，formulas for the design deflection value which are applicable to the pavement structure design of lowcost rural roads are as follows: semirigid base: 6 flexible base: where A, is the type coefficient of the road surface. The type coefficient of asphalt concrete road surface is。 that of hotmix asphalt macadam and that of emulsified asphalt macadam road surface are all 1. 1。 and that of asphalt surface treatment road surface is1 .2. (3)Allowable deflection Allowable deflection is the maximum deflection allowed at the end of the road39。 s service life under lim iting conditions in poor season. Through thoretical analysis and experimental study， the calculation for mulas for the allowable deflection of road surface which are applicable to the pavement structure design of lowcost rural roads are as follows}2}: When designing the asphalt pavement structure of lowcost rural roads, we should use formula (6) or (7 ) according to the types of roadbase to determine the thickness of asphalt pavement structure. Tensile stress Because the asphalt pavement structure of lowcost rural roads is not substantial enough and the heavy vehicles are allowed to pass over them, the maximum tensile stress should be checked by puting the stresses of the semirigid。