| Our country starts to build the cement concrete pavement in the mid 60's in last century .Since 80's in last century, along with the fast development of our country's economy, the mission of road transportation continuously increases, the cement concrete pavement get rapid development in the whole country with its advantages of high stiffness, strong ability to spread the load, good stability. The total mileage of cement concrete pavement rises to 28049 km in 1993 from 1600 km in 1980 at very fast speed. Since 1994, the mileage built in each year exceeds 10000 km. Close till the end of 2005, the total mileage of the cement concrete pavement of the country already reached 306622 kilometers. The quiet great development of the cement concrete pavement promoted the booming development of highway transportation, and produced huge social performance and economic benefit.However, as to the usage condition of the cement concrete pavement in the whole country, there are still many problems, such as the imperfect of original design theories ,the shortage of construction experience and the ignorance of maintenance, which make a lot of cement concrete pavements appear structural damages or functional deficiencies, seriously influence the usage quality of highway. In the meantime, the existence of the joint in the cement concrete pavement not only influences the flatness of the pavement and the coziness of traveling, but also easily causes emit mire , split,taking off empty and other diseases. A lot of old roads have reached or exceeded its design time limit, and appear lots of diseases through the use of several decades , no matter the bearing capacity or normal use condition can't satisfy the need of existing traffic volume, these roads have to be rebuilt or heavy repaired. On the other hand, in recent years the sharply increase of the car traffic volume ,significant increase of the car loading capacity and the severe overload phenomenon , make many concretes road which built in early days quickly destroy, and face the problems that compensation and heavy repair. The cement concrete pavement differs from bituminous pavement, once starts to appear part damage and can not be repaired in time or get appropriate maintenance will seriously influence the usage function of road and even make the pavement appear structural breakage. Sometimes even the pavementstructure hasn't broke, but its flatness, anti- slippery can't satisfy the request of vehicle to drive on ,it also need to be overlaidand taken other measures at this time. Therefore, a research to the maintenance technique of cement concrete pavement, and put forward an appropriate protecting and maintaining countermeasure, have important meaning.The scientific investigation and analysis on the cement concrete pavement have an important meaning to establishment and implement of repair project of the old cement concrete pavement. Qualitative analysis and quantitative calculation can be carried on after obtaining a cruising data. The qualitative analysis is mainly about damaged condition of the old cement concrete pavement; damaged reason analysis of the existing cement concrete pavement; repair method and principle of the cement concrete pavement. Quantitative calculation is mainly to get calculation parameter in need of pavement repair design , such as the mold quantity of the top of base, the thickness of concrete road pavement, flexural-tensile strength and elastic modulus of concrete.The damaged condition of pavement is an important index in the investigation and evaluation on road situation .The damaged condition of pavement is described with damaged types, damaged degree and damaged area. There are artificial eyeballing measure method and automatic road noodles breakage photograph car method in the method of investigation of the damaged condition of pavement. Investigating damaged condition of old pavement and analyzing the reason to rebuild the road pavement by specific method. If the pavement was seriously damaged and needed to be rebuilt, full inquisition should be conducted on the reason of the damage of old pavement, to instruct to draw up pavement and rebuilding projects.The old concrete pavement overhauled with bituminous overlay layer involves two forms of structure ,which is rigid and flexible, not only the characteristics of materials have a large variation, the influence of temperature to cement slab is great , and there are joint and crack, and often company with,taking off empty and other damage phenomenon in the old road panel, these all urge the overlay layer to appear cracks towards the position of joint and crack at the old road panel, and this kind of crack are often called reflect crack. The environment factors and negative effects such as heat inflation and cold constringency in old cement tectonic plate usually make the crack quickly expand to all sides .If the depth of crack develops to run through the surfacecourse ,then the incursion of water would not only flush roadbed, but also will directly result in the damage of bituminous surface course by the water injer, will quickly cause chip and expand of the crack with the effect of vehicle load, make the adding layer to appear serious damage, consumedly shorten the service life of the bituminous adding layer. To ensure the service life of the bituminous adding layer and keep the surface flat, the creation and development of the reflect crack have to be controlled and decelerated. Because of the joint and crack in the old cement concrete road panel can't bear to pull stress and shear stress , therefore reflect cracks are generally response to the crack and joint of old cement concrete road panel. When the old cement road panel moves, it will produce stress concentration in the adding layer on the top of crack and joint, and form reflect crack. But the movement of cement road panel is an inevitable result of temperature variety, running vehicles and comprehensive function of both of them. The reflect cracks which caused by temperature variety are usually called temperature type reflect crack, and those caused by vehicle load are called load type reflect crack. The temperature condition is different in everyplace , the transportation condition of each road segment and the structure condition of the existing pavement are also not same, as a result, the creation of reflect crack probably mainly due to temperature reason , or probably mainly due to the load effects. For circumstances of reflect crack which were mainly caused by temperature reason, the measures of lowering the glue between the adding layer and the old surface layer and improving the tensile strength of the adding layer can be adopted. According to concrete circumstances and conditions of the adding layer road segment, analyze the possible reasons of the reflect crack, thus accordingly put forward corresponding measures to prevent or defer them.The measures to prevent or defer the reflect crack of bituminous the adding layer of old concrete noodles layers the following a few kinds are as follows:(1)slice transverse joint on the bituminous the adding layer;(2)adopt thick the adding layer.(3) adopt alleviative layer of the crack(4)adopt various interlayer;(5)Fall to pieces and fix up old concrete surface course or smash old concrete surface course.Adding bituminous concrete surface course on the old cement concrete pavement is a kind of valid measure. But because it involvestwo kinds of different materials, so it's hard to analyze this kind of the adding layer with mathematics method. In theory ,the finite element sandwich(calculation program can be adopted to simulate a calculation . It takes bituminous the adding layer as the wearing course and the old concrete pavement as the base course. But because of the existence of crack, it is very hard to simulate. There isn't a uniform design method at home and abroad currently. There are mainly a few experience methods in common use ,such as the COE experience method, AASHTO experience method, AI(American bituminous academic association) method and so on.This article close mate engineering practice. It takes the rebuilding engineering of the old cement concrete pavement of the Gui-Liu express way as a study subject. Based on the investigation of the condition of this segment and the evaluation of loading ability, this text analyzes the main reason of various phenomenons of damaged pavements and puts forward settle measures aiming at different damaged condition.On the basis of drawing lessons from experiences and productions of home and abroad, through investigation of the old pavement condition and combining the need of the transportation development in future, this article carried on the design of the the adding layer structure composing which promised the rationality of bituminous the adding layer design technique, and inquired construction craft and control method of the the adding layer which promised the effect of modification. These have important academic and actual instruction meanings to investigate the evaluation of old cement concrete pavement of the Gui-Liu express way and other similar express way.Getting the following conclusions:1) Before overlaying with bituminous on the old cement concrete pavement, overall inquisition, evaluation, classification of the situation of old pavement should be regarded. According to the different classification of road situation, corresponding spreading project should be chosen.2) Before spreading bituminous surface layer, the diseases of old cement concrete slab should be valued. Combining overall investigation with objective evaluation of old pavement situation, then take corresponding processing measure for the various damaged circumstances of the old concrete pavement in order to raise the strength of old slab.3)The damage condition of the old cement pavement is very complex,and has a large variation, which make us should consider a lot of influence variables in the design of the adding layer , and difficult to ascertain design parameters; For spreading the bituminous overlay layeron the old cement concrete, our country hasn't mature design methods so far because of various technique problems haven't been resolved , however, the main factors that should be considered in bituminous the adding layer design are the strength of the old cement pavement structure and prevention of reflect crack. The thickness which gains with the different calculation method doesn't exert a homology for the same road segment. It is proper to adopt different methods to calculate in design, and carry on an analysis comparison to various results , and combine fulfillment experience to assurance the ultimate thickness of the adding layer.4)As long as we strengthen and pay attention to quality control under construction ,it is not only feasible in technique to carry on an bituminous mixture to overlay on old cement concrete pavement ,but also raises the quality of driving, improves the transportation condition, prolonged the service life of road, economized funds, shortened time limit of the old road rebuilding, have better economic benefit and social performance. The popularization of this technique has a wide application foreground.
|
PDF Full Text Request