Study On Protecting Technology Of Rotary Excavation Method In Tunnel Spoil Layer

With the continuous development of society,now our country's infrastructure construction work is massive,and an increasingly large and complicated,including housing construction,the number of Bridges in the construction of pile foundation,wide variety,difficulty of construction technology is more and more big,the traditional maneuvering drill,impact drill hole formation efficiency has been difficult to meet the need of the pile foundation construction,to a certain extent,urgent need to introduce a new type of pile foundation,high efficiency pore forming machine,rotating drill is now a more advanced construction machinery,which is flexible,high hole rate,fast construction speed,civilization and environmental protection,and many other advantages,is widely used in housing construction,highway Bridges foundation engineering construction.Currently widely used in soil,sediment layers rotating drill,compacted gravel layer and hardness is less than 50 mpa of bedrock,the construction of main pore forming process is to use can be closed,open step drill bucket bottom and the sides of the telescopic pipe driven alloy drill pipe at high speed,cut off the surrounding soil layer,will cut dig soil into the drill pipe,and then through the pipe will be filled with mud bucket proposed holes,placed in a pack of ballastless truck,to abandon dross field accordingly,so cycle that is needed for the formation of the pile hole.However the highway bridge pile foundation construction often meet cover is loose,the virtual design of geology,depth is larger,virtual design to cover large quantities,such as clear dig discharge processing,certainly will greatly affect the construction period,but also increases the construction cost.This article through to huaiji guangdong province state highway 9 standard middle bridge 1#?3#pier pile foundation located about 10m ballastless overburden tunnel hole construction as the backing,the scene using vibrating sunken tube + cyclotron drill or impact drill into construction,due to the protection of bobbin rich large hardness higher ballast,around obstacles during vibration hammer vibration was taken down,liners can't down the pressure is too small,too much pressure will lead to deviation,protection tube vibrating sunken tube can not be achieved,difficult to store in the pile hole mud,mud can't form a loop,so can't construction.Late by rotating drill combining the artificial dig-hole pile wall construction process scheme,when using a single diameter of rotary digging the drill pipe in the construction,the first lock casting concrete platform,to 80%or higher design strength,to spin dig drill core construction,concrete is formed namely lock core is complete,continue drilling 2.0?3.0m,stop to drill out,and then backfill concrete,to 80%or higher design strength,again in hole drilling construction,enterprise core core to complete the concrete wall ring form then,continue drilling 2.0?3.0 m,stop to drill out,backfill concrete again,repeat core technology,until through virtual design covering layer,the implementation of this process,the construction to the 2nd or 3rd ring,because each ring wall thickness control,the weakest of the concrete wall is only 5 cm thick,caused by a lack of breast wall stiffness,making hole appear secondary landslide,unthreatening.Improved and field practice,and finally form the rotary digging "ring connection"wall concrete technology,which USES the many kinds of the diameter of the concrete wall,from the top down,large sets of small ring ring,ring in order to meet the method,to avoid the secondary collapse caused by the weakness of the concrete wall hole phenomenon.Rotary digging "ring connection" breast wall concrete construction craft when implemented with the above basic consistent,the difference is that in before through virtual design cover screw drill pipe diameter is different,use is greater than the first design rotary digging pile diameter of 50cm drill in drilling within the virtual ballast layer,again change than last time when coring drilling small drill pipe in the construction of 20cm in diameter,in circulation,the formation of "ring" wall,makes the concrete wall thickness has been effectively controlled,breast wall stiffness significantly been improved,success through the virtual design cover.Summarizes a set of mature rotary digging "ring connection" retaining wall construction technology,gives reference for the similar condition of pile foundation.