The Application And Analysis Of Foundation Underpinning Technology In Historical Masonry Constructions

Limited to construction techniques, historical masonry constructions weregenerally laid on compacted ground without proper foundations, so there are thediseases of uneven settlement in all historical masonry constructions. One of the usefulmethods is underpinning technology. Based on historical masonry constructions liftingengineering, some key questions were studied. The major work and relevantconclusions are as follows:(1) In the underpinning engineering, the pipe jacking method is used. The effectof pipe jacking construction on the settlements of the upper wall is mainly analyzed.The upper wall is simulated to a deep beam model, based on the study of Burland, theallowable settlement formulas combined with settlement and strain are deduced, theratio of elastic modulus to shear modulus and the location of neutral axis are considered,which can be used to analyzed the allowable settlements of different wall forms. Thestrains of upper wall under settlements are analyzed by finite element software. TheRVE is used to simulate the continuity and anisotropy; the effects of wall thickness, wallopening ratio and upper load to wall strain are analyzed.(2) The opening steel pipe pile is applied in engineering, so the pile-sinkingresistance of opening steel pipe pile is analyzed. Combined with the influence factors ofpile-sinking resistance, the soil sensitivity and soil plug are considered, the pile-sinkingresistance of small diameter open-end steel pipe pile are analyzed based on themeasured dates. According to the state of soil plug, the pipe driving process is dividedinto two stages, the corresponding pile-sinking resistance calculation formulas are putforwarded, and the corresponding fitting coefficients are derived. The set up effect tothe pile bearing capacity is analyzed. Based on the dates of the set up of pile bearing capacity and exist formula, deduced the formula of considering the set up of the bearingcapacity of open-ended pile, the draw ratio and friction angle are considered in theformula. The formula satisfies the accuracy of engineering and used easily, can be usedto estimate the set up to the bearing capacity.(3) The stability of steel pipe pile is analyzed. Based on energy method,considering the resistance of pile side soil, the effective length of pile is analyzed, andthe effective length formula is deduce in the conditions of homogeneous and layeredsoil. The effect of cushion blocks to the critical bucking capacity of pile is analyzed byfinite element method. The contact element is used to simulate the interaction of pileand cushion block, cushion block and cushion block, the linear and nonlinear bucklingload is analyzed. The relation of buckling load and radial displacement is analyzed indifferent effective length. The following conclusions are deduced: the buckling load ofpile without upper cushion block is bigger than that of with cushion block; if the pile isshort, the effect of cushion block can be neglect, if the pile is long, the effect of cushionblock is decrease.(4) In the underpinning engineering of steel pipe pile, the effect of liquefaction topile stability should be analyzed. The undrained liquefaction properties of sand areanalyzed, and the peak value of sand under monotonic loading is studied. Based on theanalytical method of pile settlement in elastic soil, the particle liquefaction model ispresent. Upper the liquefaction height, the decrease of soil strength should beconsidered; below the liquefaction height, the pile can be analyzed by elastic method.The formula of liquefying depth of soil is deduced, which can be used to analysis theeffect of pile stability and revise the bucking length of pile.The main original points are as follows:1. The effect of pipe jacking construction on the settlements of the upper wall ismainly analyzed. The upper wall is simulated to a deep beam model, the allowablesettlement formulas combined with settlement and strain are deduced, the ratio of elasticmodulus to shear modulus and the location of neutral axis are considered, which can beused to analyzed the allowable settlements of different wall forms.2. The pile-sinking resistance of small aperture opening steel pipe pile is analyzed.Combined with the influence factors of pile-sinking resistance, the soil sensitivity and soil plug are considered, the pile-sinking resistance of small diameter open-end steelpipe pile are analyzed based on the measured dates. According to the state of soil plug,the pipe driving process is divided into two stages, the corresponding pile-sinkingresistance calculation formulas are put forwarded, and the corresponding fittingcoefficients are derived. The set up effect to the pile bearing capacity is analyzed. Basedon the dates of the set up of pile bearing capacity and exist formula, deduced theformula of considering the set up of the bearing capacity of open-ended pile, the drawratio and friction angle are considered in the formula.(3) Considering the soil resistance, the stability of pile is analyzed. Based onenergy method, the effective length of pile is analyzed, and the effective length formulais deduce in the conditions of homogeneous and layered soil. Based on the analyticalmethod of pile settlement in elastic soil, the particle liquefaction model is present. theformula of liquefying depth of soil is deduced, which can be used to analysis the effectof pile stability and revise the bucking length of pile.