| Qingdao North Station is located in the reclamation area of landfill. As a researchobject, the station had been monitored thoroughly during construction. The stratumfrom top to bottom is construction solid waste, municipal solid waste, argillaceoussilty clay, silty clay, rhyolite, argillaceous sandstone, tuff, etc. Solid waste layers is4~12m. The main structure of this station is constructed by open-cut method.The mainresearch includes four parts as followed:(1) Landfill garbage soil physical and mechanical properties testing: research athome and abroad for reference, the physical and mechanical properties of garbage soiltest method, test by test means the4m,8m,12m garbage landfill site soil physicaland mechanical properties, and connecting with the field measured data, given thelandfill garbage soil shearing strength index in the suggested value;(2) During the construction of the bored piles method, it found that the holecollapse become serious, it will not only affect the quality and the speed of pile, butalso cause serious waste of cement, so the garbage soil hole wall stability is a problemurgently to be solved. Bored piles based on the investigation and study of theengineering hole and the hole diameter of pile collapse phenomenon, from theengineering properties of garbage soil, leachate and waste soil layer thickness andconstruction machinery, such as factor analysis of the mechanism and reason of thesephenomena, and puts forward corresponding preventive measures, to providereference for similar engineering;(3) A mechanical behavior of solid waste during foundation pit excavation isdiscussed on the base of the in-situ monitoring results of earth pressure and fieldmeasured data in solid waste. During excavation, the soil strength increases, which ismostly because of the variances of characteristics of soil in unloading state.Measurement of earth pressure is less than computation, and the value graduallydecreases during excavation. In the end, it tends to be stable or slightly higher than theminimum. Compared with soft soil, the change is not only related to the deformationbut also the change of soil property, especially, the influence of fiber to the shearstrength of solid waste. By analyzing changing characteristics of earth pressure in solid waste, from the surface of earth within0m~5m, experience value of lateral earthpressure coefficient is0.35during excavation and0.25after excavation, and within5m~10m, the value is0.55during excavation and0.45after excavation.Theconclusions will provide the reference for future similar projects;(4) Based on the measured data of garbage soil retaining structure deformationcharacteristic and the waste soil excavation characteristics research: combined withfield measured data, the deformation and stress in retaining structure deformation,supporting axial force and the surface deformation law, this paper analysis thegarbage soil retaining structure deformation characteristics of soil and the deformationcharacteristics, and compare the three kinds of palisade structure under the conditionof the measured data. Combining numerical analysis software, the flexible supportingsystem, double row piles under the two different support forms of garbage in theprocess of soil excavation deformation are analyzed in numerical calculation, keyresearch garbage in the process of soil excavation deformation, gives a rationalcalculation model and the waste soil excavation parameters.In recent years, urban land is expanding to the surrounding areas, some oldlandfill site is planning for construction. Lacking of data about foundation pitexcavation in old landfill site, the collection of in-situ monitoring data is verynecessary. Monitoring the earth pressure on retaining structure in the solid wasteduring excavation. Combined with the engineering properties test results and the fielddata, engineering properties of solid waste during excavation could be analyzed,which will provide the reference for future similar projects. |
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