5 research outputs found
Correlation of Dynamic and Static Young’s Modulus for Limestone
The application of rock mechanics in the area of geotechnical engineering is
important especially, in describing the strength of rock material for essessing the stability of
excavations, foundations and slopes in rock. In this study, the characterization of the rock
material was investigated through the Young’s modulus parameter, which describes the
relationship between the stress applied to the rock material and the resulting strain. For an
elastic and homogeneous solid, the measurement of Young’s modulus can be determined either
from the static or dynamic measurements. Numerous studies outline the differences between
the Young's modulus obtained from static and dynamic measurement in the laboratory.
Comparatively, the measurement using static methods are more direct and realistic, as it
describes the behaviour of rock deformation until failure occurs. The dynamic methods are
more versatile and continuous, as they rely solely on the measurement of elastic wave
velocities. However, one of the most notable disadvantages of rock material characterization by
means of dynamic methods is that it overestimates the failure of rock material when compared
to its actual value. With this in mind, the aim of this study is to obtain the measurements of
Young’s modulus using both the static and dynamic methods. Based on the comparison made,
an empirical equation of Est = 0.9264 (Edy) + 0.4976 with coefficient of determination, R2 of
0.8 is obtained for estimating the static Young’s modulus for limestone. The equation is
applicable in situation where static measurement could not be carried out, and also serves as
reliable estimation of Young’s modulus from dynamic measurement
Application of a Comprehensive Rock Slope Stability Assessment Approach for Selected Malaysian Granitic Rock Slopes (Pengaplikasian Pendekatan Penilaian Kestabilan Cerun Batu Komprehensif untuk Cerun Batu Granit Malaysia yang Terpilih)
In Malaysia, rock slope stability analysis has been largely confined to kinematic analysis with rock mass rating
systems as assessment tools for stability analysis. While this method addresses the fundamental issues of rock slope
stability including identifying potential failure modes, an information gap still exists between geologists and engineers
in designing proper mitigation measures for rock slopes. This paper aims to address this issue by incorporating several
methodologies, including kinematic analysis, slope mass rating and the Barton-Bandis criterion for the limit equilibrium
method. Four rock slopes with potential instabilities namely KSA, KSB, LHA, and LHB were studied. KSA and KSB were
located near Kajang, Selangor while LHA and LHB were located near Rawang, Selangor. Each slope exhibits multiple
potential failures, with attention given on sliding-type failures in planar or wedge form. A slope mass rating value was
assigned to each potential failure based on rock mass ratingbasic and the slope mass rating based on readjustments for
discontinuity orientation and excavation method. Factor of safety from limit equilibrium method show potentially
unstable blocks and failed blocks (Factor of Safety <1.00) with confirmation on site. Water filling of discontinuity
apertures plays an important role in destabilizing rock blocks, especially in wet conditions experienced in Malaysia’s
tropical climate. Several geometries are identified as potentially unstable due to low slope mass rating (Class V) and
factor of safety of <1.2, such as planar J5 and wedge J2*J5 at KSA, wedge forming with sets J3, J4 and fault plane at
KSB, planar J2 at LHA, and wedge J3*J4 at LHB. Stabilization structures such as rock bolts can be better designed with
the determined factor of safety values coupled with relevant geological and geotechnical inputs. In this comprehensive
rock slope stability assessment approach, limit equilibrium method serves as a useful method in analyzing rock slope
stability to complement kinematic analysis and stability ratings often used in Malaysia
Seismic Interpretation and Reservoir Static Model: A Case Study in Block MFK, Riau Province, Indonesia
MFK Block was located between Kampar and Rokan Hulu, Riau Province and 135
from Pekanbaru City, Indonesia. There are 33 wells in Field X, MFK Block with 27 active wells.
This field has an area of about 79.65 km² that located in Central Sumatra Basin. The field was
discovered in 1976 and began to be produced in January 1979. Our research is focused on AK
reservoir intervals, which is also part of Bekasap formation. The main aims of this study are to
interpret field structure model, determine the distribution of reservoir properties, develop static
reservoir model for field as a reference for field performance enhancement, estimate oil reserves
in the field reservoir, and the prospect of hydrocarbons in the AK reservoir. The available data
are 2D seismic data, mudlog descriptions, well log data, and perforation data. The methods used
in this study are stratigraphic sequences, electrofacies analysis, geological structure analysis,
static reservoir modelling, and estimation of hydrocarbon reserve volumes. Based on mudlog
and electrofacies analysis, the study interval was arranged into 2 lithofacies units, namely sand
channel and sand bar. The depostion environment of Bekasap Formation is estuarine
environments. The interval of the study has an association of fasies moving northeast to
southwest. Based on the results of property reservoir analysis, facies that have good reservoir
quality is sand channel facies. Based on the static modeling method approach, the estimated
stock tank oil initially in place (STOIIP) for AK reservoir interval is 728 MBBL
Application of a comprehensive rock slope stability assessment approach for selected Malaysian granitic rock slopes
In Malaysia, rock slope stability analysis has been largely confined to kinematic analysis with rock mass rating systems as assessment tools for stability analysis. While this method addresses the fundamental issues of rock slope stability including identifying potential failure modes, an information gap still exists between geologists and engineers in designing proper mitigation measures for rock slopes. This paper aims to address this issue by incorporating several methodologies, including kinematic analysis, slope mass rating and the Barton-Bandis criterion for the limit equilibrium method. Four rock slopes with potential instabilities namely KSA, KSB, LHA, and LHB were studied. KSA and KSB were located near Kajang, Selangor while LHA and LHB were located near Rawang, Selangor. Each slope exhibits multiple potential failures, with attention given on sliding-type failures in planar or wedge form. A slope mass rating value was assigned to each potential failure based on rock mass ratingbasic and the slope mass rating based on readjustments for discontinuity orientation and excavation method. Factor of safety from limit equilibrium method show potentially unstable blocks and failed blocks (Factor of Safety <1.00) with confirmation on site. Water filling of discontinuity apertures plays an important role in destabilizing rock blocks, especially in wet conditions experienced in Malaysia’s tropical climate. Several geometries are identified as potentially unstable due to low slope mass rating (Class V) and factor of safety of <1.2, such as planar J5 and wedge J2*J5 at KSA, wedge forming with sets J3, J4 and fault plane at KSB, planar J2 at LHA, and wedge J3*J4 at LHB. Stabilization structures such as rock bolts can be better designed with the determined factor of safety values coupled with relevant geological and geotechnical inputs. In this comprehensive rock slope stability assessment approach, limit equilibrium method serves as a useful method in analyzing rock slope stability to complement kinematic analysis and stability ratings often used in Malaysia
Empagliflozin in Patients with Chronic Kidney Disease
Background The effects of empagliflozin in patients with chronic kidney disease who are at risk for disease progression are not well understood. The EMPA-KIDNEY trial was designed to assess the effects of treatment with empagliflozin in a broad range of such patients. Methods We enrolled patients with chronic kidney disease who had an estimated glomerular filtration rate (eGFR) of at least 20 but less than 45 ml per minute per 1.73 m(2) of body-surface area, or who had an eGFR of at least 45 but less than 90 ml per minute per 1.73 m(2) with a urinary albumin-to-creatinine ratio (with albumin measured in milligrams and creatinine measured in grams) of at least 200. Patients were randomly assigned to receive empagliflozin (10 mg once daily) or matching placebo. The primary outcome was a composite of progression of kidney disease (defined as end-stage kidney disease, a sustained decrease in eGFR to < 10 ml per minute per 1.73 m(2), a sustained decrease in eGFR of & GE;40% from baseline, or death from renal causes) or death from cardiovascular causes. Results A total of 6609 patients underwent randomization. During a median of 2.0 years of follow-up, progression of kidney disease or death from cardiovascular causes occurred in 432 of 3304 patients (13.1%) in the empagliflozin group and in 558 of 3305 patients (16.9%) in the placebo group (hazard ratio, 0.72; 95% confidence interval [CI], 0.64 to 0.82; P < 0.001). Results were consistent among patients with or without diabetes and across subgroups defined according to eGFR ranges. The rate of hospitalization from any cause was lower in the empagliflozin group than in the placebo group (hazard ratio, 0.86; 95% CI, 0.78 to 0.95; P=0.003), but there were no significant between-group differences with respect to the composite outcome of hospitalization for heart failure or death from cardiovascular causes (which occurred in 4.0% in the empagliflozin group and 4.6% in the placebo group) or death from any cause (in 4.5% and 5.1%, respectively). The rates of serious adverse events were similar in the two groups. Conclusions Among a wide range of patients with chronic kidney disease who were at risk for disease progression, empagliflozin therapy led to a lower risk of progression of kidney disease or death from cardiovascular causes than placebo