Study On Key Techniques Of Winter Onstruction Of Earth-Rockfill Dam With Asphalt Concrete Core

The construction quality of roller compacted asphalt concrete is greatly influenced bythe factors such as the temperature, and climate of the construction site. The adoption ofconventional construction technique in severe cold areas in winter can lead to a series ofproblems, i.e. the extention of construction period, low use efficiency of equipment, and theincrease of construction costs, etc. The study aims to solve the technique problems such asequipment selection and alteration, temperature control, technical parameters, continuousheating technique of interlayer in winter, and quality control, etc., which provides technicalsupport for the popularization of this technique in cold areas. Through the analysis ofinfluencing factors of mixed proportion of earth-rockfill dam with asphalt concrete core, andthe study of equipment selection and alteration, temperature control measures, field test inwinter and continuous heating technique of interlayer in winter, as well as the temperatureand quality control, the key construction technique problem of cofferdam of upper reaches ofKushitayi hydropower station under extreme climate conditions (temperature is-5℃～-16℃,and Beaufort scale category is3) has been solved, so as to meet the requirement of floodingrelief in April of the next year, and the construction of earth-rockfill dam with asphaltconcrete core in Kushitayi hydropower station is up to the design requirements with highquality.The conclusion is: first, to roller compact central core, then transition zone materials,new technique of continuous construction of2-3layers without interlayer heating canaccelerate the construction speed, save cost and achieve the construction aim; second, thetemperature control standard, including preheating temperature of mixing system is110～120℃, heating temperature of asphalt is160～170℃, heating temperature of aggregate is190～200℃, to mix aggregate and mineral filler for15s, then spray asphalt to mix for45s,temperature at exit is170～180℃, temperature loss of transportation process is10～15℃,placing temperature is155～170℃, preliminary compacted temperature is145～160℃, finalcompacted temperature is110～120℃, and interlayer temperature is70～80℃；third, whilethe environment temperature is under-2℃, the asphalt tube in asphalt concrete mixingsystem, pipes, valves, and dust-accumulating device are wrapped with two layers of mineral wool with resistance wire as interlayer to make measurement precision to meet therequirement. At the same time, insulation shield is put under and around the carriage of dumptruck to transport asphalt concrete. Under the climate condition of-16℃, the transportationdistance is within500m, the time is15min, the temperature loss is between10～15℃; fourth,to increase the diameter of steering wheel of XT120asphalt paver can effectively control theaxes of asphalt paving, the integrated feeder of XT120combined asphalt paver can be alteredto trailer one, which greatly upgrades the adaptability of the paver for constructionenvironment.