Search

AbstractIn rock engineering, evaluating the post-peak strength and deformation of rock is necessary. To explore the elasto-plastic behavior of sandstone in the post-peak stage, a series of strain-controlled triaxial tests were conducted under different confining pressures. According to the post-peak characteristics, a constitutive model based on nonlinear elasticity and generalized plasticity is proposed. This proposed model is characterized by the following features: (1) Nonlinear elasticity is observed under hydrostatic and shear loading; (2) the associated flow rule is followed; (3) substantial plastic deformation occurs during shear loading; and (4) post-peak softening behavior is accurately predicted. This model requires twelve material parameters, three for elasticity and nine for plasticity. The proposed model was validated by comparing the triaxial test results of Mushan sandstone at different hydrostatic pressures under dry and saturated conditions. In addition, the model is versatile; it can simulate the deformational behavior of two other sandstones. In summary, the proposed model can reasonably predict the complete stress–strain curve of sandstone.

AbstractSince a conventional petrographic analysis does not allow a systematic and detailed study on how the microscopic factors affect the macroscopic behavior of inter-layered rocks, this research adopted a numerical model, the bonded particle model, to explore the micro-mechanisms associated with the strength and stiffness of inter-layered rocks. The model was first calibrated by comparing the simulations to the actual behavior until they tally with each other. Following, the microscopic factors, including the bond strength, the bond stiffness, type of bonds and friction of particles and type of bond stiffness, are varied to study their influences. As expected, the bond strength and the bond stiffness are found to have a direct and significant influence on the macroscopic uniaxial compressive strength and stiffness, respectively. Furthermore, close observations on the breaking of bonds during the loading process reveal interesting phenomena, including the transition of shear/normal bond breaking, the type of internal fracture and the factors controlling internal failure, etc. These phenomena enlighten the interpretations about the micromechanisms accounting for the macroscopic strength and stiffness of inter-layered rocks.

Data from continuously monitored creepmeters across the active Chihshang Fault in eastern Taiwan are presented. The Chihshang Fault is an active segment of the Longitudinal Valley Fault, the main suture between the converging Philippine and Eurasian plates in Taiwan. Since the 1951 earthquake (Mw=7.0), no earthquake larger than magnitude 6.0 occurred in the Chihshang area. At least during the last 20 years, the Chihshang Fault underwent a steady creep movement, resulting in numerous fractures at the surface. Five creepmeters were installed in 1998 at two sites, Tapo and Chinyuan, within the Chihshang active fault zone. One-year results (from August 1998 to July 1999) show a horizontal shortening of 19.4±0.3mm and 17.3±0.7mm, at Tapo and Chinyuan, respectively. These annual shortening rates are in a good agreement with other estimates of strain rate independently obtained from geodetic measurements and geological site investigation. The creepmeter measurements were made on a daily basis, providing accurate information on the previously unknown evolution of creep during the year. The records of fault creep at the Tapo site thus revealed close seasonal correlation with average rainfall: the period of high creep rate coincides with the wet season, whereas that of low creep rate coincides with the dry season. Also, in comparison with the Tapo site, the creep behaviour as a function of time is complex at the Chinyuan site. Possible factors of irregularity are under investigation (thermal effect acting on the concrete basement of the creepmeters, earth tide effect, water table variations in a nearby rice field, and rainfall). The comparison between GPS measurements across the Longitudinal Valley (31mm/year of horizontal displacement) and the creepmeter measurement across the Chihshang Fault zone (17–19mm/year of horizontal displacement) suggests that there exists other shortening deformation across the active fault zone in addition to those we have measured from the creepmeters.

Chen CC, Wang SS, Chao Y, Chen SJ, Lee SD, Wu SL, Jeng FS, Lo KJ. Serum pancreas-specific protein in acute pancreatitis. Its clinical utility in comparison with serum amylase. Scand J Gastroenterol 1994;29:87-90.To compare the clinical utility of serum pancreas-specific protein and serum amylase in the diagnosis of acute pancreatitis, the study was conducted in 134 normal subjects and 70 patients (36 with acute pancreatitis and 34 with other acute abdominal diseases as control group). The serum level of pancreas-specific protein in 134 healthy adults was 29.6 ± 1.6μg/l, with 95% within 7.3-67.2 μg/1. The upper reference limit was set at 70μg/1. Serum levels of pancreas-specific protein and amylase within 12 h of arrival were significantly higher in patients with acute pancreatitis than in the control group (647.3 ± 79.3 versus 33.8 ± 4.8μ.g/1 (p < 0.0001) and 2536 ± 344 versus 175 ± 35 IU/1 (p < 0.0001)). No significant difference in the levels of pancreas-specific protein was noted between biliary and alcoholic pancreatitis or between severe and mild attacks. The sensitivity, specificity, and accuracy of diagnosing acute pancreatitis were 100%. 94.1%, and 97.1% with serum pancreas-specific protein > 70 μg/1 and 97.2%, 91.2%, and 94.3% with serum amylase >360IU/1. The result demonstrated that pancreas-specific protein may be a good serum marker in the diagnosis of acute pancreatitis.

Summary Propellant embedded anchors can be used to secure offshore platforms by rapidly anchoring them in seafloor rock. Field tests conducted by the U.S. Navy showed inconsistent results. A more promising approach seems to be modelling of anchor penetration and pullout resistance in jointed rock based on first principles.

Serum type-III procollagen aminopropeptide (PIIIP) has been considered a marker of hepatic fibrogenesis. In an attempt to evaluate the clinical significance of serum PIIIP in patients with hepatitis B virus (HBV)-related liver diseases, the levels of the peptide were measured in 66 healthy adults and 200 patients with HBV-related liver diseases. As compared with the healthy adults (12.3 ± 3.1 ng/ml), the serum PIIIP levels were significantly elevated in patients with acute hepatitis (17.4 ± 6.6 ng/ml), chronic persistent hepatitis (18.3 ± 4.9 ng/ml), and inactive liver cirrhosis (22.1 ± 7.1 ng/ml). The PIIIP levels in patients with chronic active hepatitis (CAH) (33.9 ± 23.1 ng/ml) were the highest among HBV-related liver diseases and had a tendency to increase with the severity of CAH. Of the liver-diseased patients with serum PIIIP levels greater than 30 ng/ml, 91% had a recent episode of severe hepatocellular damage, whereas 56% of patients with greatly elevated serum liver aminotransferase levels had no associated high increase in serum PIIIP levels. Thus, we suggest that fibrogenesis in HBV-related liver diseases is initiated by severe hepatocellular damage, but liver damage can also take place without prominent hepatic fibrogenesis. Serum PIIIP may be a serum marker to predict the active fibrogenesis of HBV-related liver diseases.