The Research Of Construction Technology For Super-deep Pile Under The Complicated Geological Conditions

More than 40 meters deep in-situ concrete pile construction has been common in the bridge construction,but in the complex geological conditions which is different from the silt soil,whether in construction machinery or pile construction methods,both of them have put forward the higher request than the traditional construction technology.Catic My TOWN Commercial Area B project is located in Lanxin Avenue which is in two-way town of Chongqing Yubei District.The construction area of the project is about183676 square meters,most of it is one basement,partial is two basements.The project has included six 14-16 storeys high buildings.There are 1105 pile foundations in the project and the diameters of them are 1000 mm,1200mm and 1500 mm,232 pile foundations are in the garage position and 873 are in the main building.The length of the pile foundations are between 17-73 m,10% of the total number is between 10~20m,35% of the total number is20 ~ 30 m,30% of the total number is 30 m ~ 40 m,20% of the total number is 40 m ~ 50 m,5% of the total number is 60 m ~ 70 m.Site belongs to shallow weathered and denuded hills landform areas.Since the large areas of the field are completed move plant land,so the depth of the backfill is greater.According to the early earthworks information,the deepest depth of the filling is 68.8m.The characteristics of the soil are loose,poor stability,bedrock face steep ups and downs,no rules;While the diameter of Upper backfill section of the solitary stone is large,the largest up to 3-5 meters,when the pile foundations construct are easy to sticking and not easy to determine the bedrock surface.In this paper,the complex backfill situ pile construction has been researched,and achieved the following results:(1)According to the design depth of pile and geological prospecting of soil conditions,the project has completed the increased torque and power head extended mast design;(2)Designed a new line reaming drill bit which effectively reduces the resistance of rock breaking sense by changing the direction of the force,saving the cost of steel,and make the construct carried out more smoothly;(3)Designed a new casing which can assemble on site construction,and recyclable.It isimproving the construction speed and saving the cost;(4)Not only the empirical data that for control of materials and construction during the process of pouring concrete has been concluded,but also gave the methods and suggestions for solving the occupying the space of machine and walk way.(5)The pile construction process has been systematically summarized,and the application results were multifaceted assessment of costs,working hours,pile quality,environmental impact,etc.It has achieved expected effect of study.The findings in this article are concluded through the actual construction of 1105 pile foundations.It is the most reasonable construction process.The findings can guide the site management and construction of the similar projects.