CRD Method Research Articles

The Comparative Study on the Impact of Tunnel Excavation with Footage Different CRD to Testability of Surrounding Rock

This article used Geotechnical Engineering General Software FLAC3D to simulate the tunnel CRD method under 1.5m, 2.0m, 2.5 m, 3.0 m footage separately and analysis the influence to the tunnel surrounding rock stability in the different footage construction. This paper selected a real tunnel project as the research object and analysis comparatively the rule and characteristic of various methods of tunnel surrounding rock displacement, stress distribution and the plastic zone size through simulated computing the different footage construction. The results show that,Ⅰ.Considered from the surrounding rock stress control that the 1.5m footage adjacent formation stress adjustment effect is best, next is 2.0m, 2.5 m, 3.0 m;Ⅱ.Considered from the plastic zone size that the 1.5m footage control effect is best, next is in turn 2.0m, 2.5 m, 3.0 m;ⅢConsidered from the surrounding rock displacement control that 1.5 meter footage adjacent formation control effect is best, but 2.0 meter, 2.5 meters and 3.0 meter phase differences are not big.

Shallow depth of the tunnel excavation response research based on CRD method

Most bids of Dalian Metro are carried out with shallow tunneling method. However, for the section of Xianggong Street Station of Line 2, the geologic condition, which is mainly composed of strong-weathered rock, is so poor that it brings great difficulties in tunnel excavation. To solve the problem of stability of surrounding rock, numerical simulation and field monitoring are used to analysis the displacement field, stress field and plastic zone in every step of construction which use CRD method and also though the contrast of both consequence, The safety of the construction process has been studied and analyzed. The result not only has important guiding meaning after the construction of the tunnel, but also provides the reference for the design and construction of similar projects.

New ECCC assessment of creep rupture strength for steel grade X10CrMoVNb9-1 (Grade 91)

A first assessment of creep rupture strength for steel grade X10CrMoVNb9-1 (Grade 91) was performed by ECCC in 1995. The results were included in the European standard EN 10216. Due to a significant increase of test data and test duration it was decided in 2005 to make a re-assessment of the extended database. Different procedures have been used independently by different assessors. The method with the best overall fit of the data set has found to be the ISO CRD method. This is characterized by a two steps procedure: in the first step the mean isotherms are evaluated from the test data, afterwards the evaluated isotherms are used for averaging by a Manson–Haferd master-curve. The results have been chosen as the basis to specify long term creep rupture strength values in a new ECCC data sheet for X10CrMoVNb9-1 (Grade 91).

Cavity ring-down lossmeter using a pulsed light emitting diode source and photon counting

A new mode of cavity ring-down measurements in which an incoherent, broadband light emitting diode (LED) is used as the spectroscopic source is described. Light from a pulsed LED (570 nm, 12 nm FWHM) was coupled into a 32 cm linear optical resonator and a ring-down waveform obtained on a gated photon counter. Cavity time constants observed were on the order of 3–4 µs, yielding effective optical path-lengths in excess of 1 km. In an effort to demonstrate the function of the instrument we have measured absorption and Rayleigh scattering by gases introduced into the measurement cell. Measurements of Rayleigh scatter by CO2 and 1,1,1,2 tetrafluoroethane (R-134a) were used to calibrate the instrument. The Rayleigh extinction coefficients determined through the LED–CRD method were found to agree with literature values to within 12% on average. In an additional set of experiments, a laboratory-generated vapour containing either iodine or ozone was introduced into the measurement cell in an effort to demonstrate the technique's ability to monitor absorbing gases. The ring-down time constants (τ) observed were found to decrease by 15–75% when the absorbing gases were added to the measurement cell. The observed decrease in cavity time constant was proportional to the quantity of absorbing gas within the measurement cell. Minimum detectable extinction coefficients (2s) of ≈2.5 × 10−7 cm−1 were achieved. The LED–CRD approach may lead to development of inexpensive gas sensors or monitoring systems for atmospheric extinction/visibility.

Using CRD method for quantification of groundwater recharge in the Gaza Strip, Palestine

Using CRD method for quantification of groundwater recharge in the Gaza Strip, Palestine

Uji coba pembuatan sol karet cetak sesuai SII 0944 – 84 sistem cetak “hand press”

The trial on making of rubber sole fulfilling the SII 0944 – 84 with hand press molding system was using rubber compound on the formula of : RSS I 100 parts; Reclain rubber 30; ZnO 3; Carbon black 60; Paraffinic oil 6; Stearic acid 2; PBN 1; MBT 0,5; MBTS 0.5; TMT 1 and Sulfur 2. The vulcanization condition with time interval 0.5 minutes. Physical testing of rubber sole trial result, statistical evaluation with CRD method for determining vulcanization time for resulting optimal physical testing. Optimal physical test value was reached on the time of vulcanization 6 to 7 minutes and temperature of vulcanization between 150-160 0 C.