Study On Mechanical Behavior Of Spilt Anchorage Caisson Foundation Under Long-Term Lateral Load

Spilt anchorage caisson foundation is a new type of caisson foundation. This thesis is based on the project of "long-term bearing evolution and performance design of deep foundation under complex environment", which is a branch of the national 973 project named "study on the disaster control and bearing performance design of extra-large-span bridge". Based on the laboratory model test, mechanical behaviors of split anchorage caisson foundation under long-term lateral load are studied. The main work and conclusions are as follows:1. Due to the interaction of the two individuals of the split anchorage caisson foundation, the ability of anti-overturning of the foundation was improved compared with usual caisson. Under the same load, the center of rotation of the foundation is lower than the usual caisson. So split anchorage caisson moves in the same lateral direction accompanied by a small rotation, comparing with the obvious rotation of the usual single caisson.2. The laboratory model tests of the split anchorage caisson has been carried out in sand to investigate the optimum distance between the two caissons of the foundation. The results show that the reasonable distance is about 2 times the length of the former or latter caisson’s side-length, which is parallel to the direction of the lateral load.3. According to the laboratory model test, influence range of lateral load is about 2 times the side-length of the total split anchorage caisson’s (including the length of the soil between the two caissons), which is parallel to the direction of the lateral load.4. Using the traditional sensors and the membrane pressure sensors and the PIV test method, the full and half model tests of split anchorage caisson in remolded saturated clay were designed and carried out to study the lateral displacement, the earth pressure distribution of the former (latter) caisson’s sidewalls and bottom, and their evolution with time, when the foundation was loaded by the lateral load. This can provide experiment data for the design method when considering the affection of soil creep.5. According to the fitted long-term experimental data fitting, got the P-Y curves were obtained which can be used in the theoretical calculation of split anchorage caisson. The influence of lateral load loading time and the depth of the foundation was taken into consideration when fitting the P-Y curves.6. A simplified theoretical calculation method of split anchorage caisson was established according to the distribution of the lateral loads and restrict moments of the former and latter caissons of the foundation. For the single caisson, the lateral bearing capacity of split anchorage caisson by time can be calculated use the software named Lpie and Matlab, and the fitted P-Y curve, considering the computing width.7. The theoretical calculation method was applied an engineering case to check the validation of the method for practical application. The results show that the proposed method in this thesis is useful for the practical projects.