In this article, the computational methodology of the catenary–train–track system vibration analysis is presented and used to estimate the influence of vehicle body vibrations on the pantograph–catenary dynamic interaction. This issue is rarely referred in the literature, although any perturbations appearing at the pantograph–catenary interface are of great importance for high-speed railways. Vehicle body vibrations considered in this article are induced by the passage of train through the track stiffness discontinuity, being a frequent cause of significant dynamic effects. First, the most important assumptions of the computational model are presented, including the general idea of decomposing catenary–train–track dynamic system into two main subsystems and the concept of one-way coupling between them. Then, the pantograph base vibrations calculated for two train speeds (60 m/s, 100 m/s) and two cases of track discontinuity (a sudden increase and a sudden decrease in the stiffness of track substrate) are analyzed. Two cases of the railway vehicle suspension are considered – a typical two-stage suspension and a primary suspension alone. To evaluate catenary–pantograph dynamic interaction, the dynamic uplift of the contact wire at steady arm and the pantograph contact force is computed. It is demonstrated that an efficiency of the two-stage suspension grows with the train speed; hence, such vehicle suspension effectively suppresses strong sudden shocks of vehicle body, appearing while the train passes through the track stiffness discontinuity at a high speed. In a hypothetical case when the one-stage vehicle suspension is used, the pantograph base vibrations may increase the number of contact loss events at the catenary–pantograph interface.
The article presents problem of non-uniform foundation of structures in weak wet subsoil. The problem is illustrated with the case study of two-chamber-reinforced concrete water tank constructed in 1920s of 20th century, which cracked during construction. Under part of foundation, where the peat was found, the concrete piles were introduced.
The results of five-year measurement of crack widths with crack gauges and geodesic measurements of vertical displacement of tank were presented. These results indicate that the tank is not stable and part of broken tank supported on piles is movable.
On the basis of the presented data, the general conclusions concerning the non-uniform founding of tanks are formulated.
Iman Faridmehr, Mohammad Reza YazdaniPour, Mohammad Javadi Jokar and Togay Ozbakkaloglu
Water seepage is one of the most important features of embankment dams. To prevent and reduce seepage, it is necessary to seal the dam. Plastic concrete cutoff walls are one of the most efficient methods in waterproofing the foundation of embankment dams on permeable alluvial substrates. Sufficient resistance to loads, low permeability to maintain dam sealing, high ductility compatible with the foundation and deformation under load without cracking are the main requirements in plastic concrete cutoff walls. In this paper, the construction and implementation of the cutoff wall of Karkheh Dam, which is one the world’s largest water sealing projects, was studied. In addition, a numerical model using Seep-3D software was developed to evaluate the efficiency of the cut-off wall to decrease the seepage over the dam’s foundation. The numerical results validated by instrumentation statistics resulted from 17-years dam operation. According to the results, after the drainage of the reservoir, the cutoff wall optimally reduced the hydraulic gradient by 0.08 from 2.35 and the water leakage by 3.1 m/s from 18.3 m/s.
Sara Rachdi, Emad Jahangir, Michel Tijani and Jean-François Serratrice
This paper presents an enhanced constitutive model integrating deviatoric hardening with a modified yield surface for overconsolidated clayey soils in a general framework of Cam-clay type models. Its performance was assessed with the simulation of drained and undrained triaxial tests on three clays at different consolidation states in comparison to two critical state models. The proposed model satisfactorily estimates the shear resistance, while capturing the smooth nonlinearity of the soil response.
Shear triaxial tests at constant mean pressure were performed on an overconsolidated marl to study the shear response. Their simulation attests the importance of deviatoric hardening integration.
Hala Hammadeh, Farzat Askifi, Andrzej Ubysz, Marek Maj and Amjad Zeno
This paper presents an experimental investigation of the discharge flow pressure in the vertical silo and the hopper due to the use of insert (top cone with trunk cone bottom). Using the Insert inside the silos is one of the proposed solutions to avoid the problems of having funnel flow pattern, which has a significant effect on the distribution of flow pressure exerted on the silo wall and the hopper. The experiments were performed on a metal cylinder prototype; corn was used as a granular material, and the wall and hopper pressure distribution was measured by a special pressure transducer. The experiments revealed an important result in the flow pressure due to the change in the location of the insert. The experiments were conducted in Damascus University laboratories.
Imad Kadiri, Younès Tahir, Omar Iken, Saïf ed-Dîn Fertahi and Rachid Agounoun
Extractive industries often use explosives to destroy rocks, and productivity requirements tend to increase the charges of the explosives. The blasts induce vibrations, which result in a potential damage of the surrounding structures. Therefore, the prediction of vibrations should be described with accuracy, in order to ensure the safety of engineered structures. However, the prediction of vibrations’ levels remain a complicated issue, because it involves numerous parameters correlated to the quarry site.
In this paper, statistical analysis based on the peak particle velocity (PPV) and the attenuation law has been carried out to assess the safety charges (Q) for different distances (R) between the blast and the considered structure to secure. Moreover, the experimental investigations were conducted on the quarry site of “Sococim”, which is located on the south coast of Senegal. To ensure the safety of the “Conveyor belt” and “Panel 1 (Upper exploitation level)” sites, the PPV should be less than 10 mm/s. In fact, the attenuation model has been used to assess the safe charge weights of the explosive (Q) to be used at the “Conveyor belt” site and at the “Panel 1 (Upper exploitation level)” site. Therefore, the safe charge weights per delay (Q) were respectively 116 kg and 13.75 kg.
This work presents the geotechnical problems occurring in the interaction area between road embankments and the bridge structures in case a subsoil characterised by complex and complicated geological and engineering conditions. These significant problems that occur during the design, performance and exploitation of the abutment structures, are illustrated on the example of engineering practice in Lower Silesia, concerning a road embankment that constitutes access to the bridge. The results of numerical analyses concerning the process of consolidation of low-strength soils and their impact on the settlements of road embankment indicate the need to carry out such analyses also in the cases, when the soft soils occur in the direct geotechnical layer under the designed embankment. The Authors included in this article a discussion regarding other effective actions and solutions that can be used in the design and performance phase, leading to the elimination or reduction of problems concerning the connection of engineering structures with road embankments, which have been recurring for years, ultimately resulting in the improvement of quality, comfort and safety of road exploitation.
This article presents the results of tests on the energy properties of sedimentary rocks in the Upper Silesian Coal Basin. The rocks were tested both in an air-dry state and in a water saturation state. Samples of sedimentary rocks were collected from boreholes drilled in the underground workings of coal mines located within the area of the city of Jastrzębie, in the areas of the Chwałowice Trough and Rybnik Trough (south-western part of the Upper Silesian Coal Basin) and in the Main Trough. Influence of saturation condition on the values of the tested energy parameters was observed. The values of elastic energy and dissipated energy obtained for the samples tested in water saturation were lower compared to the values obtained for samples tested in air-dry state. As observed, an increase in the values of the given types of specific energy corresponds to an increase in the uniaxial compression strength in air-dry state and in water saturation state. Results of the tests are original and they can be applied while analysing the possibility of the occurrence of some dynamic phenomena and hazards in mine workings in Carboniferous rock mass in the Upper Silesian Coal Basin, caused by mining operations.
The main issue of the paper is the estimation of soil hydraulic permeability based on the DMT test. DMTA, DMTC and SASK methods performed in the Nielisz dam, Stegny and the SGGW Campus of the Warsaw University of Life Sciences sites are described. The article presents the implementation of the dilatometer Marchetti test (DMT) in the determination of soil fraction and effects of its occurrence in the subsoil, tested in the Nielisz dam located in the Wieprz river valley in the Lublin province, and in various sites in Warsaw (Stegny site and SGGW Campus of the Warsaw University of Life Sciences). In order to acquire the needed data, the flat dilatometer test (DMT) method was used. A direct and indirect pressure methodology of interpreting soil swelling was characterized in the article. The paper shows the possibilities of determining sand, silt and clay soil fractions based on po and p1 pressures from dilatometer tests (DMT) and the effective (σ’vo) and total (σvo) vertical in situ overburden stress. Additionally, the main advantage of this paper is the proposal of use of a new chart to determine hydraulic permeability and soil fraction, based on DMT tests.
Kheira Boutouba, Ismail Benessalah, Ahmed Arab and Ahmed Djafar Henni
Sands reinforced by hydraulic binders (cement) have constituted in recent decades a major asset for the expansion of several areas of engineering. The mechanical behavior of sand-cement mixtures has undergone some controversies studied on the Chlef sand. In this paper, we present an experimental study to investigate the mechanical behavior of a sandy soil reinforced by a hydraulic binder (cement), using the direct shear apparatus emphasizing on the shear strength characteristics and the vertical deformation variation of cemented reinforced sand. The parameters used in this study are mainly: relative density (Dr = 80%), normal stress (σn = 100, 200, 400 kPa), water content (3, 7 and 10%), cement content (2.5, 5, 7.5 and 10 %) and cure time (7, 14 and 28 days). The experimental results show that the mechanical characteristics in terms of internal cohesion (C) and internal frication angle (φ) give a better mechanical performance with the binder inclusion, and the cure conditions play an effective role on the improvement of the shear strength. This result also showed that 10% of the cement content gave us a maximum value of shear strength and an optimal influence on the mechanical characteristics. The addition of cement not only improves the shear strength of soil, but also provides diversity in the resistance against the deformations imposed load, which can be established by a dilatant character.