| Summary: | 碩士 === 國立臺北科技大學 === 土木工程系土木與防災碩士班（碩士在職專班） === 103 === A tilted 8-story reinforced concrete building with 1-story basement on a thick soft clay deposit is leveled with a special two stage grouting program.After looking into all the possible alternatives to level this building,grouting method is selected because of two reasons.The first is that the concentrated high grouting pressure at injection point is distributed over the rigid mat foundation and will not damage the integrity of the building itself.The second reason is that the unoccupied basement provides free and easy access to install grouting tubes and other controlling units and computer.
The first grouting stage conducted by injecting mild setting grout through sleeved pipe is used to stabilize soft soil zone in depth.Due to the low permeability of clay,the grouting mode in clay is usually governed by fracture pattern which also allow the re-grouting at the same injection point.As soon as the foundation soil is hard enough to act as a reaction block,the second stage of grouting is conducted.Since the soils below the mat foundation is a 2-meter thick silty sand layer.In which quick setting grout is injected right under mat foundation to jack and level building.The fracture grouting can generate higher pore water pressure than compaction grouting due to easy traveling of low-viscosity particulate grouts in soil.Therefore re-grouting is needed to improve the normally consolidated or lightly to heavily overconsolidated condition, and any subsequent grouting activity will generate only negative pore pressure, so that re-settlement will not occur and final grouting efficiency is dramatically improved.
The grouting duration at each grouting tube and grouting order of each cycle monitored by a central processing computer is scheduled each day based on the elevation surveying results.The elevated volume of mat foundation due to grouting and re-settled volume from excessive pore water pressure dissipationd are estimated from the elevation surveying results.This can be used to evaluate the grouting efficiency and verify the building being successfully and permanently leveled.
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