| The soil nailing foundation pit retaining structure (SONFOPIRS) has become the mainstream in the domestic deep foundation pit retaining construction. In order to ensure the construction safety, the security monitoring must be ensured entirely through the construction course. In the active national code, the accumulated horizontal displacement is used as the SONFOPIRS security monitoring alarming criteria, which is the Result Control Methodology and has the limitation in the practical applications. Aiming at this, the SONFOPIRS horizontal displacement development security monitoring Trace-Control Methodology and the SONFOPIRS horizontal displacement development security-monitoring model is set up in this dissertation. According to the methodology, the SONFOPIRS horizontal displacement development is limited in the security trace-control curve from beginning to end, so that the accumulated horizontal displacement is controlled in one threshold parameter. As the decision-making basis of the construction project, the existing horizontal displacement monitoring result can be used to monitor and control the SONFOPIRS construction course effectively.The dissertation completes the following works:(1) Some horizontal displacement forecast theories on the SONFOPIRS have been analyzed and studied including the time-sequence analysis, the Artificial Neural Network, the Gray Color Forecast, the Failure Cause Tree Analysis and so on, and then such conclusions are given: these forecast models have their applicability respectively, however, they mainly focus on "forecast" instead of "security control", and the study methods centralize in rationalism deduce, and some forecast models are so complex that not easily to spread and apply.(2) A great deal of projects' deformation field survey data have been analyzed, and a dozen of typical project cases' horizontal displacement development rules have been studied with various sites, lithology and dialect construction procedures: the field survey horizontal displacement data in the construction course are draw on the displacement-time coordinate system as the test points, with the distribution of these points or the developing trend of these points forming curves, their horizontal displacement-time curve can be concluded, and then the SONFOPIRS horizontal displacement development rule can be studied and its approximate shape of thedisplacement-time curve can be judged.(3) After trying on some functions such as the hyperbola, index and logarithm, finally, the S-shapecl and the arctan functions are confirmed as the fitting ones for horizontal displacement-time curve. The research indicates: When being used to fit the horizontal displacement-time curve, the S-shaped curve has an abrupt change feature as a whole, although the regression parameters a and b have the closest linearity relation, therefore it is not suitable to use as the security monitoring. With its displacement-time model closes the survey curve with maximum, the arctan function model can be determined as the security displacement-time curve.(4) The horizontal displacement security-monitoring model is validated in the dozen of typical project cases: the correlative parameters are applied in the model's formula and draw their security displacement-time curve. After comparing with the survey curve, the security displacement-time curve is proved that its shape and development trend is consistent with the survey one.(5) Practical application: the SONFOPIRS security monitoring model is applied in two new building projects in Zhengzhou, the correlative parameters are applied in the model's formula and draw their security displacement-time curve before surveying, which are used as the control criteria of the SONFOPIRS construction course. The surveying data in the construction course are draw on time and compared with the security displacement-time curve. The alarming is given to the construction while the surveying data exceeds the security displacement-time curve. The project application indicates that the S... |
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