Study The Settlement Behavior Of Bridge Pile Foundation In Deep Soft Soil Of High Speed Railway In China And Over-Consolidated Soft Soil Of Highway In Iraq

The design of high speed railways need for very strict requirements of settlement control. The settlement calculations of deep bridge foundation suffer from many obstacles and inaccuracy. Therefore, there is a need for the accurate methods of calculations to match the reality in the field.The study of measuring the settlement values of the Bridge in Beijing-Shanghai High-speed Railway with the time and load is considered in this dissertation. The settlement is measured using the single-point settlement gauge and hydrostatic level. The results of field test show a new field measurement method to calculate the compressed layer thickness. A single settlement account with a single point measurement is used to overcome the difficulties, when the base bottom layer cannot be stable anchorage in the soft soil or rock layer be difficult to monitor. Field tests showed that the deep pile support layer compression thickness is closely related to soil properties.This dissertation is also a study on the behavior and prediction of settlement values of bridge pile foundations due to construction loads. The settlement is predicted using hyperbolic model and statistical regression. The field measurements are compared with the hyperbolic model results and those predicted by the statistical regression. The Neurofuzzy System (NFS) used in this dissertation to predict the settlement of deep pile foundations. The results obtained from this system give good agreement and high accuracy for prediction of settlement compared with hyperbolic model and statistical regression analysis. Also, this scenario can be applied for similar or more complicated problems in the Geotechnical engineering.A new formula for compression modulus modification that calculated from compression modulus provided by geotechnical test under pressure of100-200kPa along thick soft soil is proposed in this dissertation. Based on the new formula, comparative analysis of group piles settlement by existent national specifications is carried out. This finding modifies the codes calculations which are lack the accuracy and confidence of settlement calculations in the deep soft soils. Method of stress control is used to control compressive layer thickness, and adopted to calculate settlement of long friction group piles in thick soft soil. Through comparison with the field data, settlement values by this method using the modified compression modulus are close to the measured values, which prove the applicability in calculating settlement in thick soft soil.The dissertation also discusses the design and analysis of a bridge foundation subjected to load of train with three codes, namely AASHTO code, Code for Design of Building Foundations (GB50007-2011) and Code for Design on Subsoil and Foundation of Railway Bridge and Culvert (TB10002.5-2005). The study focuses on the design and analysis of bridge foundation and find which code is better to control the problem settlement due to the applied loads. Settlement of the bridge is calculated depending on the data collected from the project site. The vertical ultimate bearing capacity of single pile for the three codes is also discussed. The results indicate that the AASHTO code is safer in the bearing capacity of single pile, while Code for Design of Building Foundations (GB50007-2011) gives a good indicator of the risk to foundation settlement.The finite element Plaxis3D Foundation program is used in the analysis with the new empirical equation to modify the input parameters represented by the soil compression modulus. The results of the numerical analysis using the proposed empirical equation provide insight to the settlement analysis of pile groups in soft clayey soils and the finite element Plaxis3D program can be a useful tool for numerical analysis. In this dissertation, the numerical analysis calculations are modified using the correction formula to calculate the compression modulus from those obtained in the test which modify the results of the settlement and thus become close to the reality. The numerical finite element analysis produced accurate results as compared to the statistically derived equations and those calculated by hyperbolic model analysis.This dissertation finally studies on the Al-Rumaitha Bridge lies in the Muthanna province, south of Iraq, including the soil investigation taken from the project and settlement analysis for the designed bridge firstly manually according to the data provided, secondly using two and three dimensional Plaxis Foundation program of finite elements. The settlement calculated by the above three ways is nearly similar, and the results can be modified using the proposed formula in this dissertation. The bearing capacity of the bridge is also calculated and its value is larger than the applied load due to the effect of truck loading. The study found that this bridge can be used in the highway and can success for this purpose.