The Analysis On Influential Factors And Control Indicators Of Roadbed Broaden In Reconstruction Project Of First-class Highway

In the design and construction process of first-class highway reconstruction project and operation stage, the differences between the new and old roadbed settlement is unavoidable. To analyze the key influencing factors and control standard problems of differential settlement in widening first-class road subgrade, the paper basing on a practical engineering, selecting finite element analysis software of ABAQUS and finite element method, using unidirectional saturated soil consolidation theory, this paper calculates on the first class road widening subgrade differential settlement, analyzes the influence of the factors such as the roadbed broaden the width, height of embankment and subgrade modulus of subgrade modulus to differential settlement, and gets the following research conclusions from studying widening subgrade differential settlement control index in the Angle of design, construction and pavement structure using:(1)This paper Analyses the main disease forms of first-class highway roadbed widening engineering, and summarizes the cause of subgrade differential settlement mainly including widening insufficient roadbed compaction degree, high filling embankment, the insufficient intensity integration of the new and old roadbed and so on, and it should be taken effective engineering measures to avoid or reduce uneven settlement in each link of design and construction.(2) Broaden the settlement changing curve is generally been "scoop" sharping, though the overall level of equivalent stress is not big between old roadbed and widening subgrade, the top position in middle of the new widening subgrade appears stress concentration phenomenon, it should be taken measures such as placing the geogrid between the old and new embankment to prevent stress layer leading to structure destruction in the practical widening subgrade construction.(3) By the method of orthogonal experimental design, this paper does the comprehensive analysis on the four key factors including roadbed broaden width, height of embankment, subgrade filling modulu and subgrade modulus, takes the vertical surface settlement and horizontal displacement as evaluation indexes, and concludes that the most influence factors on the vertical settlement is roadbed broaden width.(4) The analysing Of different roadbed broaden ways under different broaden width of top of the subgrade settlement shows that after the width of roadbed broaden increasing to 8 m, widening subgrade settlement location appears the slope effect, and suggestes the advisable unilateral broaden width is from 8 to 12 m.(5) From the analysis of the top widening subgrade differential settlement changings in different subgrade soil broaden height shows that widening subgrade differential settlement values increase gradually with the increasing height of the subgrade soil; The elastic modulus of subgrade soil impacts new broaden subgrade section most, with the elastic modulus increasing, the top new broaden uneven settlement tends to decline, when in construction the properties of subgrade soil must be in strict test for guarantee.(6) The proposal is under construction completion taking the horizontal slope deviation i is less 0.3% as control indicators of testing road engineering construction quality, the road surface changing slope rate i is less 0.46% as differential settlement control standard for pavement structure using phase from research; The fitting equation concluding limiting values of differential settlement of roadbed widening S, the ratio of new and old subgrade widen values l, elastic modulus ratio of new subgrade filling k and subgrade height h, can veritably reflect the internal law between factors and differential settlement control indicators, which may provide some references for design and construction in actual roadbed widening engineering.