Study On The Supporting Technique Of Foundation Trench Of Meirengong Building In Xiamen City

Since the policy of reform and opening carried out in China, the special economic region, Xiamen city has developed rapidly. More and more foundation trenches appear. But engineering accidents also follow because the supporting technique of foundation trenches is so complicated, fargoing and diverse. Foundation trench supporting has become the most challenging technique in construction engineering. This dissertation mainly focused on the supporting technique of foundation trench of Meirengong Building in Xiamen City.Meirengong Building is the high-rise of the old city reconstructive project firstly presented to Xiahe Road in Xiamen. Because it is located in downtown area, detonation or slope cutting are not permitted. The author conduct a series of research work including the supporting system design, construction, monitoring and mixture ratio tests of mortar for anchoring in this research. Some research results of applicable value in engineering are presented also.(1) Contrast experiments on mortar with five kinds of mixture ratio have been conduced. The results indicate that the strength of mortar with early-strength admixture and UEA expansion admixture will improve largely. This kind of adglutinate mixed with U expansion admixture can grip anchor bolts tightly even underwater, as can be seen from the pull-out type tests for anchor bolts when the mortar age is over 10 days.(2) The author lays the supporting piles as a arched shape. This layout can transform the axial force of circular beam into a force which parallels the axial. Compression strength of the concrete on circular beam can bring into play adequately. The displacement of the pile top will also reduce effectively. The whole stability of the supporting structure improves.(3)Rock bolts are used as an extension of the supporting piles. This structure solves the embedding problem of cantilever pile and is newly applied in foundation trench in China. No environment contamination appears in this old crowed town because no detonation or mechanical drilling.(4) Diameter of bore for anchor bolt is 50mm, and diameter of reinforcing steel bar is 28mm. Both break through the rules which request that the bore diameter should be bigger than the steel bar diameter trebly or not smaller than the steel bar diameter adding 50mm.(5)The monitoring results of horizontal displacement along the pile in length indicate that pile bottom is not a fixed end as assumed. Displacement also occurs on the pile bottom. Assuming pile bottom as a elastic support will be more correct.(6) Displacement of soil around the foundation trench is associated with theatmospheric precipitation. Precipitation uplifts ground water level and weakens shearing strength of soil, thus results in large displacement in side direction. Catch well is not suitable for foundation trench drainage in this project, and should be adopted carefully in similar building sites.