ROCK SLOPE SURFACE STABILITY ANALYSIS: A CASE STUDY ON HON LON ISLAND, KIEN HAI DISTRICT, KIEN GIANG PROVINCE, VIETNAM

The research aimed to study 24 rock slope surfaces along the road around Hon Lon Island, Kien Hai district, Kien Giang province, Vietnam. The analytical results have determined slope failure, wedge failure, and toppling, which occurred on almost slope surface and the average percentage of plane failure is the largest. The average percent of plane failure is 19.23%, the wedge failure is 15.35%, and the toppling fault is 6.73%. Besides, the analytical results have also identified the slope surfaces which can be the key blocks: ND-13, 18, 23, 25, 34, 37, 45, 51, 62, 63. The other analytical results show that the existence of key blocks at the rock slope surfaces in the N-S direction, dip to E at the survey locations: ND-13, 23, 63 and dip to W at the survey locations: ND-37, 45; in the NE-SW direction, dip to SE at the survey locations: ND-15, 62 and dip to NW at the survey locations: ND-18, 34; in the NW-SE direction, dip to SW at the survey location ND-51. These results have important significance to support for protecting slope surface safety.

Environmental and Economic Impact of Retrofitting Techniques to Prevent Out-of-Plane Failure Modes of Unreinforced Masonry Buildings

This paper presents an innovative methodology to assess the economic and environmental impact of integrated interventions, namely solutions that improve both structural and energy performance of existing masonry buildings, preventing out-of-plane modes and increasing their energy efficiency. The procedure allows the assessment of the environmental and the economic normalized costs of each integrated intervention, considering seismic and energy-saving indicators. In addition, the work introduces in relative or absolute terms two original indicators, associated with seismic displacement and thermal transmittance. The iso-cost curves so derived are thus a powerful tool to compare alternative solutions, aiming to identify the most advantageous one. In fact, iso-cost curves can be used with a twofold objective: to determine the optimal integrated intervention associated with a given economic/environmental impact, or, as an alternative, to derive the pairs of seismic and energy performance indicators associated with a given budget. The analysis of a somehow relevant case study reveals that small energy savings could imply excessive environmental impacts, disproportionally increasing the carbon footprint characterizing each intervention. Iso-cost curves in terms of absolute indicators are more suitable for assessing the effects of varying acceleration demands on a given building, while iso-cost curves in terms of relative indicators are more readable to consider a plurality of cases, located in different sites. The promising results confirm the effectiveness of the proposed method, stimulating further studies.

Numerical Prediction of Failure in Unidirectional Fiber Reinforced Composite

Fiber-reinforced polymer composites exhibit orthotropic mechanical properties and particularly low strength in the out-of-plane direction. The use of classical failure criteria that consider transverse isotropy to evaluate these composite materials implies an overestimation of their out-of-plane strength, which could lead to a nonconservative and even catastrophic design. The Molker failure criteria developed for orthotropic materials consider the LaRC05 failure modes as a basis, with two additional failure modes for the out-of-plane direction of noncrimp fiber (NCF)-reinforced composites. Given the similarity in configuration and orthotropic behavior of unidirectional fiber fabric reinforced composites to NCF-reinforced composites, Molker failure criteria are implemented and applied in this research to determine the initiation of out-of-plane failure in unidirectional fiberglass fabric composites. The criteria are programmed in the form of a module coupled to a constitutive model available in a finite element method (FEM) package. Then, the mechanical properties and failure parameters of the unidirectional fiber-reinforced composite are determined. Model validation is accomplished by comparing numerical and experimental results of out-of-plane failure in a corrugated panel. In addition, several failure criteria used in unidirectional fiber-reinforced composite that consider transverse isotropy are evaluated. The results of critical load at the onset of transverse out-of-plane failure obtained by using the Molkerorthotropic criterion prove to be superior in accuracy compared to those obtained with the criteria commonly applied to this type of materials.

Analytical and Experimental Investigations on Mechanical Properties of Weak Plane Bedding in Mudstone

Wellbore instabilities frequently occur in mudstone formation with weak plane bedding because of strong anisotropies. The mechanics parameters of weak plane bedding are of vital significance to the wellbore stability analysis for mudstone formations. The conventional method for determining the mechanics parameters is to fit lots of triaxial test data due to the blindness of coring. In this paper, an evaluation method of the mechanics parameters of weak plane bedding is proposed to improve the accuracy of weak plane bedding mechanical properties. The mechanics parameters of weak plane bedding are obtained by combing the single-weak plane failure criterion with the compressive strength of rock obtained by the triaxial test of cores with different coring angles. It is seen that the new evaluation method is simple and convenient. On the other hand, a validation method of the mechanics parameters of weak plane bedding is proposed to ensure their accuracy. The compressive strength obtained from the core with the special coring angle is compared with the theoretical compressive strength for verifying the accuracy of weak plane bedding mechanical properties. It is observed that the proposed evaluation and validation methods can be used to measure the value of weak plane bedding mechanical properties precisely. The proposed methods are general and can be used for measuring the mechanical properties of fracture weak-plane and joint weak-plane.

Geomechanics Insights for Successful Well Delivery in Complex Kutch - Saurashtra Offshore Region

Subsurface lithofacies sequences encountered in the Kutch & Saurashtra Basin has its own set of challenges brought about due to its complex geological settings. These challenges are related to drilling, logging and completion and demand rigorous planning for the upcoming wells with detailed analysis of hazards associated with the overburden and reservoir rocks. In the study, these challenges are found to be linked with three prime geological sequences. Detailed integrated geomechanical analysis with inputs from drilling parameters, real-time formation experience, geophysical and geological are conducted for the improvement in borehole condition and improvising the effective drilling rate. A customized geomechanical workflow has been adopted to construct Mechanical Earth Model (MEM, Plumb et al., 2000) for strategic wells across the basin. Wellbore stability events related to geomechanics were reproduced and analyzed. The cause of the events was established and mitigatory methods were proposed. In addition, stress orientation along the wellbore trajectory and across the basin was estimated using breakouts identified on images and multi-arm calipers. Fast shear azimuth from Dipole Shear Sonic anisotropy analysis was also integrated to provide more robust and accurate estimates. Wells in the region are characterized by slow ROP, high torque and drag, wellbore instabilities (severe held ups, cavings, stuck pipes, string stalling etc.) and challenges while logging and running casing. The study has characterized these challenges and identified required solutions linked to the three geological sequences - weak Tertiary, Late Cretaceous Deccan Trap and Early Cretaceous to Jurassic clastic formations. The Tertiary formations are relatively weak (UCS∼300 to 1500psi) and prone to sanding and cavings due to breakouts. MEM based mud weight window estimation predicts that shear/failure hole collapse can be prevented using 10ppg to 11ppg mud weight. The formations below the Deccan Trap are locally categorized under Mesozoic sequence. The Deccan Trap and Mesozoic formations are extremely hard, tight, extremely stressed, heavily fractured and in some areas are also of HPHT nature. Rock strength shows a wide variation (UCS ∼5,000psi to 25,000psi) making bit selection a difficult task. Borehole failure is complex and cuttings analysis shows the signature of both shear and weak plane failure. Fractures on the image logs, rotation of breakouts, and fast shear azimuth support this theory. Mixing fracture sealing agents along with the use of optimal mud weights is found to be the most likely drilling solution. The understanding developed in the region and implementation of recommended steps assisted in successful drilling of two recent wells wherein gun-barrel shape borehole condition in both Tertiary and the Mesozoic sequence was achieved. The non-productive time was reduced by nearly 40 days increasing the effective ROP by 40%. In addition, smooth borehole prevented any major issues while carrying out casing and cementing operations.

Numerical Simulation of Unreinforced Masonry Buildings with Timber Diaphragms

Though flexible diaphragms play a role in the seismic behaviour of unreinforced masonry buildings, the effect of the connections between floors and walls is rarely discussed or explicitly modelled when simulating the response of such buildings. These flexible diaphragms are most commonly timber floors made of planks and beams, which are supported on recesses in the masonry walls and can slide when the friction resistance is reached. Using equivalent frame models, we capture the effects of both the diaphragm stiffness and the finite strength of wall-to-diaphragm connections on the seismic behaviour of unreinforced masonry buildings. To do this, we use a newly developed macro-element able to simulate both in-plane and out-of-plane behaviour of the masonry walls and non-linear springs to simulate wall-to-wall and wall-to-diaphragm connections. As an unretrofitted case study, we model a building on a shake table, which developed large in-plane and out-of-plane displacements. We then simulate three retrofit interventions: Retrofitted diaphragms, connections, and diaphragms and connections. We show that strengthening the diaphragm alone is ineffective when the friction capacity of the wall-to-diaphragm connection is exceeded. This also means that modelling an unstrengthened wall-to-diaphragm connection as having infinite stiffness and strength leads to unrealistic box-type behaviour. This is particularly important if the equivalent frame model should capture both global in-plane and local out-of-plane failure modes.

A critical review based on Fault Tolerance in Software Defined Networks

SDN (Software-Defined Networks) is an incipient architecture of decoupling control plane and data plane involved in dynamic management of network. SDN is being installed in production based networks which ultimately lead to the need of secure and fault tolerant SDN. In the present investigation, we are discussing about the kind of failures with label happen in SDN. A critical survey based on the recently proposed mechanisms for handling failures in SDN. Initially, we discussed with the help of tabular data involving mechanism of data plane failure. We also discussed the various mechanisms for handling misconfiguration of drift able of switches and control plane failure handling mechanisms. We also epitomize issues with both data and control plane mechanism that are discussed earlier. In the end, we are stating that there is need of build much efficient and secure mechanism for SDN networks.

Identifikasi potensi longsoran lereng pada kuari batugamping menggunakan analisis kinematika

Kestabilan lereng adalah faktor penting pada pekerjaan penambangan kuari karena berkaitan dengan keamanan dan keselamatan pekerja dan peralatan. Kestabilan lereng dipengaruhi oleh beberapa faktor di antaranya dimensi lereng, sifat fisik dan mekanik batuan, struktur geologi batuan serta faktor gaya luar yang bekerja pada lereng tersebut. Pada studi ini, kestabilan lereng diprediksi menggunakan analisis kinematika berdasarkan jenis gerakan material lereng, tanpa menganalisis gaya-gaya penyebab material lereng tersebut bergerak, sehingga yang diamati adalah fenomena struktur batuan berupa arah utama bidang diskontinuitas. Tujuannya adalah memprediksi kemungkinan arah dan terjadinya longsoran lereng. Faktor yang diperhitungkan hanya arah bidang diskontinuitas terhadap arah bidang lereng, sudut kemiringan bidang diskontinuitas dan sudut kemiringan bidang lereng. Hasil analisis menunjukkan beberapa lereng berpotensi longsor dengan tipe planar (plane failure) dan baji (wedge failure). Dari 10 lokasi pengukuran yang ditentukan secara acak, diketahui ada 4 lokasi berpotensi longsor planar 4 dan 5 lokasi longsor baji. Dalam hubungannya dengan arah dan kemiringan lereng, potensi tersebut terjadi di 4 lokasi pengukuran, sedangkan di lokasi lainnya diperkirakan aman karena tidak searah dengan bidang lereng. Kekar dan rekahan tidak menunjukkan arah dominan tertentu tetapi terdapat tendensi pada kwadran 2 dan 4.

Creating the finite element mesh of non-periodic masonry from the measurement of its geometrical characteristics: a novel automated procedure

This paper presents an automated procedure that enables the creation of a finite element mesh directly from the image file representing the rasterized sketch of a generic masonry element. This procedure goes under the name “pixel strategy” if a 2D finite element mesh is needed, where the elements are planar and rectangular; conversely, its extension in the 3D case is named “voxel strategy”, and there the resulting finite elements are solid bricks. The finite element meshes so obtained are then used for extracting homogenized in-plane failure surfaces for historical masonry cells, which display a non-periodic arrangement of units. These surfaces are consistent with the expected results, and their shapes suggest that the behavior of such type of masonry may range between orthotropic (if bed mortar joints are clearly noticeable) and quasi-isotropic (if some units spread over two or more masonry layers).