Ground Treatment Technology For Bumping At Bridge Heads Of Operating Highways In Deep Soft Soil Areas

The construction of highways in China’s coastal areas must pass through a large number of deep soft soil foundations,and large-scale bridgehead jump problems have occurred during long-term operation,which has seriously affected driving safety and comfort.For maintenance in the form of a new one,a brand new technical solution for the treatment of bridgehead jumps in operating roads in deep soft soil areas is required.The thesis takes the "Yongtaiwen Expressway Wenzhou Section Overhaul EPC Project" as an example of the project,and takes the bridgehead jumpover management of the entire project as the background.By strengthening the foundation of the bridgehead and restricting the lateral displacement to control the settlement,a technical solution for the operation of the bridgehead jump of the operating highway in deep soft soil is proposed,namely "artificial hard shell + lateral pile".In order to verify the feasibility of the program,a series of theoretical and numerical analysis studies were carried out: the total settlement of the untreated foundation and the artificial hard shell layer was calculated by the layered sum method,and the 90% solids were predicted according to the consolidation theory The time required for the degree of completion;using FLAC3 D software to explore the effect of seepage-stress coupling,the technical solution to the settlement control of the foundation,combined with theoretical and numerical calculation results to determine the effectiveness and engineering feasibility of the solution.This paper has made the following progress through research:(1)Analyzed the achievements and experiences of current experts,scholars and engineering technicians in controlling the problem of bridgehead jumps on soft soil operating highways,and summarized the ideas and methods for the management of highways in soft soil areas.(2)Through on-site engineering geological survey work,select the bridgehead foundation under typical working conditions as the research object,obtain relevant site data and physical and mechanical parameters of rock and soil.With reference to the existing theory and engineering practice experience,combined with on-site geological survey data,the treatment plan of "artificial hard shell layer + lateral pile" was proposed,and the plan was designed in detail.(3)Based on the layered sum method,the total settlement of the untreated foundation and the artificial hard shell foundation were calculated respectively.According to the consolidation theory,it is predicted that it will take 25 years to reach90% consolidation.Considering that the highway has been in operation for 10 years,the settlement will be basically stable after 15 years.(4)According to the on-site geological data and design plan,FLAC3 D is used to establish the three-dimensional numerical model calculation of seepage-stress coupling under the action of embankment self-weight load,and the development trend of long-term settlement of the expressway with time is analyzed and calculated.(5)Use the established three-dimensional numerical model to simulate the "artificial hard shell" and "lateral pile" technical solutions,discuss the impact of hard shell thickness,pile length and pile spacing on displacement,and simulate four working conditions separately to obtain different working conditions.Cloud map of conditional displacement.By comparing the displacement cloud diagram and analyzing the settlement-time trend,combined with the theoretical calculation results,the control effect of the scheme on settlement is determined.After adopting the technical scheme for foundation treatment,the settlement was effectively reduced by 35.7%,and the consolidation degree reached 86% after 15 years.(6)According to the results of theory and numerical analysis,a technical solution for the treatment of road bumps in soft soil is proposed: a 6m artificial hard shell layer is constructed on the foundation by sloping jet grouting on both sides of the embankment,and two rows are arranged at the slope foot Pile structure,pile length 15 m,pile spacing 3.5m.After treating the foundation with this technical scheme,the settlement control ratio reached 30%～40%.With reference to the relevant specifications and engineering experience,the technical scheme was determined to meet the engineering settlement control requirements,and the feasibility and effectiveness of the scheme were verified.The results of the paper will provide model and data support for post-construction settlement prediction,and provide a new idea and direction for the management of highway bridgehead jumps in deep soft soil areas,which is of great significance to ensure the safe operation of highways.