Research On Adaptability Of Load Cell Under Complex Working Conditions

With the rapid development of China’s infrastructure construction,pile with large tonnage,large diameter as well as large length have been widely used in bridge and house construction.In order to ensure the quality and safety of buildings,bearing capacity of the pile is regarded as one of the necessary inspection items in many pile foundation codes.Compared with the traditional static load test,the self-balancing static load test,which is not restricted by the site and easy to operate,has better detection efficiency.Additionally,it greatly saves the detection cost and detection time leading to widely application in all kinds of pile foundation detection.Although it is an advanced detection technology at present,the problems existing in the application process is also growing with the widely application of self-balancing method,such as jack sealing performance and displacement measuring devices,load cell structure in the form of the density of concrete pouring box equipment factors such as the output value,the influence of load and load cell installation construction factors will affect the success rate of test,in order to adapt to the rapid development of pile foundation,it is necessary to upgrade the self-balancing test technology.According to practical engineering,this paper firstly summarizes the existing problems in the application of self-balancing method by collecting field test data of self-balancing method,and systematically studies and improves the test equipment of self-balancing method.Subsequently,the factors affecting the load cell output value are analyzed by using grey correlation analysis method,and the multiple regression analysis model of the load cell output value is established by using mathematical statistics correlation theory.On this basis,the upgraded load cell and other equipment were successfully applied to the actual project,and the construction technology of the new type load cell was analyzed.In addition,the research results promote the innovation and application of the self-balancing method,which has good practical value and engineering significance,and has created great economic and social benefits.The following research results are obtained in this paper:(1)Aiming at the shortcomings of displacement measuring devices,jacks and traditional load cell structures,a systematic study was carried out in this paper.An electronic displacement detection device is developed to make the displacement measurement of load cell more accurate.The special jack of load cell was improved,and the stopping ring and sealing device were added on the original basis,which limited the measuring range of the jack and effectively solved the problem of hydraulic oil leakage.By optimizing the load cell structure,a kind of hollow structure load cell and a kind of integral structure load cell suitable for pipe pile are designed to solve the problem of the influence of traditional load cell structure on concrete casting,which leads to the noncompactness of pouring.(2)In order to ensure the quality and design efficiency of load cell,according to verification specification requirements of the load cell,a kind of loading test device of multi-functional new-type load cell is developed,which has two kinds of detection: the overall reaction of verification of the load cell and jack pressure maintaining test.Furthermore,it is strict to ensure the production quality of the load cell and make full use of resources.A load cell standardized design software is developed,which can meet different engineering needs and design the optimal load cell and draw design drawings in the shortest time so as to reduce the workload of designers to improve work efficiency and achieve the standardized design of load cell.(3)By sorting out and analyzing 30 groups of self-balancing test data,the influence of the pile length,pile diameter,load location,friction resistance of the soil around pile and bearing capacity of the soil of pile tip on the output value of the load cell are found out by using the grey correlation analysis method.The results shows that the correlation degrees of each factor to the load cell output value are 0.9617,0.9314,0.8381,0.9525 and 0.9349,respectively,which indicates that the correlation degree of pile diameter is the biggest and that of load cell position is the smallest.(4)The multiple regression calculation model of the influence of different pile foundation parameters on load cell output value was established by using mathematical statistics related theories,which is verified by using mathematical statistics F test method,and the results were significant.Besides,the reliability of the calculation model is verified by an engineering example,and the output value of the load cell can be estimated by the calculation model,which provides a reference for the design of the load cell.