Research And Application Of The Pile Foundation Construction Technology In Lhasa Stadium

With the fast development of engineering construction in Plateau, high altitude and anoxic region in our country, the traditional construction method for foundation pile will result in difficulty for construction, low efficiency for personnel and equipment. Rotary drilling and cast-in-situ bored pile method has advantages such as flexible and convenient, large output torque, fast to pore-forming, strong adaptability to formation, low energy consumption and high quality of drilling hole over other methods. So it is suitable for the pile construction of frozen earth and extreme climate in Qinghai-tibet Plateau.Based on the analysis of existing related literatures and the engineering survey data, and combined years of study and work experience accumulated in the construction process, the author adopt rotary digging hole and double sleeve technology to solve the difficulty for construction, low efficiency for personnel and equipment problems.Taking the pile foundation engineering of Lhasa Stadium as an example, this paper analyzed the high altitude climatic conditions, engineering geology and hydrogeological conditions in the local. Then the construction process and the operating points of the drilling of the rotary drilling rig in the plateau area and post-pressure grouting technology were summarized. At last, the quality standard and quality control measures of rotary drilling bored pile were concluded, which would provide technical support for construction quality. The technology of double sleeve process was developed creatively to eliminate the effect of the soil frictiona above the foundation during pile test. It was successful to integrate the stage of test pile into the foundation pit support stage, which made the foundation pit support and pile test conducted simultaneously. Thus the time to support the foundation pit and test piles was saved.Through the designing and processing of double sleeves, pile foundation construction and pile foundation testing, static load test for single pile, the new technology has showed its advatanges in eliminating part of side friction resistance of invalid soil part of foundation pile. The results of high strain detection showed that the total resistance of the pile is greater than the design ultimate bearing capacity, which meets the design requirements. The low strain detection results showed that the pile is intact and no defect is found. And all of the piles are category?. The static load test showed that the eigenvalues of the vertical compression bearing capacity of the tested piles(32m, no post grouting and 35 m, without post grouting) are not less than 750 k N and 1400 k N, respectively, and the corresponding eigenvalue of the bearing capacity is 1.35 Mm to 1.58 mm and 2.06 mm to 2.23 mm; The eigenvalues of the vertical compression bearing capacity of the tested pile(35m, post grouting) are not less than 1900 k N, and the eigenvalue of the corresponding bearing capacity is in the range of 2.46 mm ~ 3.29 mm, which meet the design requirements. The eigenvalues of the vertical pullout capacity of single pile are not less than 400 k N, and the corresponding eigenvalues of the bearing capacity are in the range of 0.96 mm ~ 1.27 mm, which meet the design requirements. The eigenvalues of the horizontal bearing capacity of the tested single pile are 200 k N, and the maximum displacement is within the range of 0.58 mm ~ 0.83 mm, which meets the design requirements. The process can improve the quality of the pile and significantly shorten the construction period. Moreover, it could be a reference to similar projects in the next decades.