Study On Settlement Calculation Of Filling Engineering With FCB At The Back Of Bridge Abutment

Highway traffic plays an important role in boosting the economic development and improving quality of life for people. In recent years, the highway construction have made great progresses in China, the highway mileage is rapidly increasing and the quality of road construction has been continuously improved. But there are still many technical challenges to be studied and resolved, the "abutment bump" phenomenon occurring in the soft roadbed nearby bridge abutment is one of them. As a part of the project of science and technology of Hubei Provincial Highway Bureau,the scheme of filling with foamed cement banking(FCB) in the back of bridge abutment is adopted to reduce post-construction settlement and eliminate "abutment bump" phenomenon. Combined with the construction practice, the research of settlement calculation and the design of FCB filling structure is conducted to provide guidance for on-site construction in the FCB backfilling project. The main research work and achievements obtained in this paper are as follows:(1) Through the analysis of the mechanism of "abutment bump" phenomenon,the two ultimate reasons for this are addressed in this paper: the excessive differential settlement and big longitudinal slope of the soft roadbed after construction. Based on the consolidation mechanism of soft ground, the relationship among the total settlement, consolidation settlement, construction settlement and the post-construction settlement is analyzed in this paper to find out a feasible method to calculate the post-construction settlement of the pavement behind the bridge abutment.(2) Compressive strength tests are conducted on FCB which is made based on different mix design to study its mechanical properties and a formula to describe the relationship between the compressive strength and elastic modulus is proposed in this paper. Combined with the morphology of FCB taken by SEM, the relationship between the micro-structure and mechanical properties of FCB is studied to provide guidance for the research of mix design of FCB.(3) The settlement calculation model based on layer-divide summation and the model based on finite element method are established to study the characteristics ofthose two methods of settlement calculation in this paper. Compared with the settlement calculation result of layer-divide summation method, the calculation result achieved based on finite element method is more reliable. Because the hypothesis for FEM settlement calculation model is less than layer-divide summation does and the interactions between abutment, slab and the filling structure are taken into account.(4) The study on the design of the properties and the structure of FCB is carried out in this paper when it is used for filling at the back of bridge abutment. The FEM method is used to study the influence the design scheme of mechanic property and structure of the FCB backfilling does on differential settlement in the back of bridge abutment. The result of the research shows it is a effective measure to reduce differential settlement at the back of bridge to raise compressive strength or reduce bulk density of FCB.(5) The production process of FCB, construction procedure and some caveats are introduced in this paper when FCB is used for on-site construction, the effects of filling construction is analyzed and evaluated, and then the successful experiences of the application of the FCB construction techniques are summarized in this paper.(6) According to the practice of on-site construction, such a FCB filling scheme was adopted: the compressive strength level of FCB is CF1.5 and bulk density of FCB is W7 and the length of the top of the filling structure is 11 m and the bottom is7 m. Combined with the construction scheme, the prediction research about post-construction settlement is carried out. The calculation result shows the differential post-construction settlement is 2.17 cm and maximum differential slope is0.38% at the back of bridge abutment, which are both less than they are entitled to,that is to say the "abutment bump" even "the second bump" problem is solved when the back of bridge abutment is filled with FCB according to the designed FCB filling scheme for on-site construction mentioned above.