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RISS 인기검색어
- 검색키워드
- 저자 : Mohd Ashraf Mohamad Ismail (검색결과 3 건)
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Mohd Ashraf Mohamad Ismail,Soon Min Ng,Ismail Abustan 대한토목학회 2017 KSCE Journal of Civil Engineering Vol.21 No.6
Horizontal drains are commonly used in stabilizing slopes. This paper presents a case study of slope failure in Precinct 9, Putrajaya, Malaysia which buried 23 cars and caused the evacuation of 1000 people from their apartments. Recorded data showed that it had been raining heavily with a total cumulative rainfall of 210 mm two days prior to the slope failure occurrence. Post failure investigations suggested that the slope failure is caused by the rise in groundwater level that increased the pore water pressure thus reducing the shear strength. Therefore, horizontal drains were proposed as a remedial measure to enable the lowering of groundwater level to a safe level. Parametric study was carried out to determine the suitable length and ideal location of horizontal drains installation. Geophysical electrical resistivity survey was carried out to determine the ideal location for installing the horizontal drains. The Finite Element seepage analysis and Limit Equilibrium method were used to examine the effect of horizontal drains on slope stability during rainfall. The minimum length required for the horizontal drains is 22.5 m and the best location for installation is at the toe below the lowest berm of the slope. Field monitoring results from piezometers and measurements of discharge rate verified that the installation of horizontal drains are able to lower the groundwater level effectively.
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Mazlina Razali,Mohd Ashraf Mohamad Ismail,Andrew Lee Kwan Yee,Raja Asyraf Azizan Raja Adnan,Kenichi Kawano,Kensuke Date,Yasuhiro Yokota,Sharan Kumar Nagendran,Zuraini Zainal 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.8
The in-situ elastic modulus (E) is a vital parameter for describing rock strength in many engineering projects on rock slopes. The elastic modulus and uniaxial compressive strength (UCS) are typically investigated via laboratory tests using core samples. However, the direct determination of E is costly and time-consuming in preparing many intact samples from highly weathered Setul limestone. The knocking ball testing method is a non-destructive test that can quickly and easily obtain the elastic modulus of rock in-situ by striking the surface of a rock mass with a spherical steel hammer. This study presents the relationship between the elastic modulus of knocking ball (Ekb) and the uniaxial compressive strength of the Schmidt hammer (UCS-Schmidt). Results show that the regression coefficient correlation, R2 is 0.851, indicating a positive trend with a few outliers. The measured Ekb were also verified with mineral propertiesand correlated to differential weathering grades to confirm the accuracy of measurement results. The finding compared to previous similar studies tested on several types of rock show a statistically significant. This research highlights the effectiveness of the knocking ball method for determining the modulus of rock slope at different weathering grades. A high elastic modulus corresponds to a high uniaxial compressive strength, verified by the laboratory test. This study shows that the knocking ball can be useful for predicting in-situ elastic modulus.
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Soon Min Ng,Mohd Ashraf Mohamad Ismail,Ismail Abustan 대한토목학회 2015 KSCE JOURNAL OF CIVIL ENGINEERING Vol.19 No.6
A massive slope failure occurred on the 22nd March 2007 after 3 days of continuous rainfall at Precinct 9, Putrajaya, Malaysia. Back analysis carried out identified that the main cause of failure is due to the existing high groundwater level within the cut slope. It is also observed that the continuous discharge from the horizontal drains yield approximately 100 ml/s even during dry season. Thus, it is suspected that the main contribution to the high groundwater level is due to the leakage from the large water tank constructed on the crest of the slope. Electrical resistivity survey was adopted to facilitate the investigation for the source of high groundwater level within the slope. A 3-dimensional resistivity model was developed using the Inverse Distance Weighting (IDW) interpolation method. The 3D resistivity model shows that the high water content zone is not caused by the leakage of water tank but is originated from an unknown source at the south-east side of the slope.
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