Study On Differential Settlement Controlling Technology To Widen Sandy Roadbed In Yellow River Flood Area Of The Henan Easten

From the view of satisfying with the growing traffic,improving the service level,developing thelong-term ecnomic and transport requirements,the repairment and expansion to the national highway is the themeof highway construction.As the silty soil has distributed in large areas in our country, and even some roads inthese areas can not meet the needs of the traffic, so it is necessary to study the nature of aeolian sand soil,theeffection to widen the the silty soil roads and difference settlement control technology.First this paper does experimental study on the physical characteristics, chemical character andMechanical Characters of silty soil in the east of Henan province combining the distribution and maincharacteristics of silty soil. Some research was done on road broaden projects, and analyzes the advantages anddisadvantages of several silty soil road broaden project and the choice of such projects; Second through the finiteelement, we can analyze the factors caused differential settlement and the method to control differential settlement.Last do indoor experiment research on slope cutting, excavation step and paving geogrid at the joint of old andnew subgrade combining with the three fine sand subgrade broaden models. And already got some results.Silty soil aspects: summarize the different properties of domestic silty. Experiments show that thediameter of the silty in the east of Henan province is between0.074mm and0.100mm, plasticity index is about5.4,the capillary water height is about109cm, the total content of SiO2, Al2O3, CaO is more than90%, the bestmoisture content is about10.2%and the maximum dry density is1.93g/cm3.All silty soil are medium or lowcompressibility soil, internal friction angle is13°or so and the cohesion is small.Silty sandy subgrade broaden aspects: The finite element software analysis and indoor experimentsshow that with the increase of widened width to bilateral and unilateral the biggest differential settlement value of embankment top is bigger. The differential settlement value of bilateral widen is smaller than unilateral widen,bilateral widened has obvious advantages. The bigger of subgrade height and the smaller of compression modulus,the subgrade settlement value and differential settlement value will be bigger. The settlement of embankment topand the maximum differential settlement value will decrease with the increase of new and old subgrade modulus.The settlement of embankment top decrease with the increase of slope cutting gradient, but the maximumdifferential settlement value will increase. The settlement of embankment top and the maximum differentialsettlement value decreased with the increase of excavation step width. The settlement of embankment topincreases with the increase of excavation height, the maximum differential settlement value will increase first thendecrease. After the processing of gravel pile, the settlement of wet and soft embankment top and the maximumdifferential settlement decreased with the increase of length of gravel pile, quantity of modulus, the quantity ofsoil modulus between gravel piles, the cohesion of soil. After the processing of cement power spraying piles, thesettlement of wet and soft embankment top and the maximum differential settlement decreased with the increaseof length of gravel pile, quantity of modulus, the quantity of soil modulus between gravel piles, the cohesion ofsoil. Compared with grave pile, cement power spraying pile is better. The paving of geogrid can reduce the literaldisplacement of new subgrade to a certain degree. And pave at the basement and the top is the best. The lowerlevel of the geogrid the smaller of the differential settlement.