摘要 :
Standard mica was used to correct the X-ray powder diffraction instrument error and mathematic methods were employed to find the correction equation. By analyzing mullite sample and comparing the corrected and uncorrected analysis...
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Standard mica was used to correct the X-ray powder diffraction instrument error and mathematic methods were employed to find the correction equation. By analyzing mullite sample and comparing the corrected and uncorrected analysis results we found the former is obviously more reasonable. So the conclusion is that the X-ray powder diffraction instrument error greatly affects the crystalline structure analysis, and the above method is convenient and effective for the correction of instrument error.
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摘要 :
The strain monitoring and stress analysis of a new type of post-prestressed tunnel liner were carried out.The instrumentation block of the tunnel liner, with the dimensions of 12.06 m in length, 6 500 mm in diameter, and 650 mm in...
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The strain monitoring and stress analysis of a new type of post-prestressed tunnel liner were carried out.The instrumentation block of the tunnel liner, with the dimensions of 12.06 m in length, 6 500 mm in diameter, and 650 mm in thickness, was post-prestressed with the unbonded tendons, each of which consists of 8 pieces of double-looped strands and the axial spacing of the tendons is 500 mm.Concrete strain meters, rebar meters, Ioad cell and zero-stress meters were installed for the strain monitoring.The tensioning loads were applied incrementally in three cycles (50%, 77% and 100%) at the concrete age of 28 d and the tensioning work lasted for 187.1 h.Strain readings were taken before and after each cycle during tensioning period and at the specified time interval after tensioning period.It is found that concrete creep developed over tensioning period is 30% of total strain and 41.5% of elastic strain respectively.Prestress force in the unbonded tendon and concrete stress in the liner were evaluated according to the observed strain variations.Both of them are time-dependent, and about 5.3%, 8.3% and 9.0% of the prestress losses are observed at the age of 1 d, 30 d and 60 d respectively after stressing.The distribution of prestress in the liner is relatively uniform and meets the design requirement.
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