Investigation of Shear and Static Pullout Behavior of Geocomposite Embedded in Two-Layers soil

Cost-effectiveness, fast performance, and relatively long service life have made geosynthetics widely used in geotechnical structures such as road pavement, retaining walls, slope stabilization and foundations, bridge abutments, embankments or at the boundary between embankments and subgrade to be used. The soil geocomposite used in this research, which is made in Iran under the brand name of GC Soil 40/40, is a combination of geogrid and geotextile and is used in various projects such as embankment bed reinforcement and separation to implement embankment on fine and loose subgrade. In general, in the design of geosynthetics, including soil geocomposites, interaction mechanisms including slip and pullout as well as interaction coefficient between soil and geosynthetic should be considered. Accordingly, to evaluate the soil-geocomposite interaction, direct shear and pullout tests were performed in one-layer soil (sand-geocomposite and gravel-geocomposite) and two-layers soil (sand-geocomposite-gravel) under different vertical stresses. The results of direct shear tests showed that reinforcing the soil with geocomposite reduced the angle of friction and increased soil adhesion. Despite the increase in shear stress and pullout resistance with increasing vertical stress, the interaction coefficients decrease with an increase in the vertical stress. This issue can be related to the nonlinear behavior of pullout force and soil-geocomposite shear stress with vertical stress. Vertical stress is an effective factor to increase the pullout resistance and type of mode geocomposite rupture and also has a significant effect on the displacement at the maximum pullout resistance. The results showed that under the same loading conditions, the placement of the geocomposite on the common surface of the two layers soil changes the pullout behavior compared to the one-layer soil. In general, it can be stated that the soil-geocomposite interaction, in addition to vertical stress, is sensitive to the type and size of soil particles, one- and two-layers of soil. For sand-geocomposite and gravel-geocomposite interfaces, the average coefficients of interaction( ) for direct shear are 0.8 and 0.91, respectively. Also, the average pullout interaction coefficients() for sandy and gravel soils reinforced with geocomposite (one-layer) are 0.35 and 0.47, respectively, and this coefficient is obtained as the average of 0.51 for sand-geocomposite-gravel (two-layer)

Using Micropiles to Improve the Anzali's Saturated Loose Silty Sand

Today, with the daily advancement of geotechnical engineering on soil improvement and modification of the physical properties and shear strength of soil, it is now possible to construct structures with high-volume and high service load on loose sandy soils. One of such methods is using micropiles, which are mostly used to control asymmetrical subsidence, increase bearing capacity, and prevent soil liquefaction. This study examined the improvement of Anzali's saturated loose silty sand using 192 micropiles with a length of 8 meters and diameter of 75 mm. Bandar-e Anzali is one of Iran's coastal populated cities which are located in a high-seismicity region. The effects of the insertion of micropiles on prevention of liquefaction and improvement of subsidence were examined through comparison of the results of Standard Penetration Test (SPT) and Plate Load Test (PLT) before and after implementation of the micropiles. The results show that the SPT values and the ultimate bearing capacity of silty sand increased after the implementation of the micropiles. Therefore, the installation of micropiles increases the strength of silty sand improving the resistance of soil against liquefaction

Efficient scheduling algorithms for real-time service on WDM optical networks

In this paper we study, the problem of providing real-time service to hard and soft real-time messages in wavelength division multiplexing (WDM) optical networks. We propose and evaluate a set of scheduling algorithms which schedule message transmissions in single-hop WDM passive star networks based on specific time constraints. We compare the performances of our algorithms with that of the typical WDM scheduling algorithm which does not consider the time constraint of the transmitted messages by discrete-event simulations and an analytical model. We find that the improvement on real-time performance can be attributed to our scheduling algorithms where the time constraint of messages has been taken into consideration. This study suggests that when scheduling real-time messages In WDM networks, one has to consider not only the problem of resources allocation in the network but also the problem of sequencing messages based on their rime constraints

Z. The Journal of Supercomputing, 13, 111132 1999

Parallel computing on clusters of workstations is receiving much attention from the research community. Unfortunately, many aspects of parallel computing over this parallel computing engine is not very well understood. Some of these issues include the workstation architectures, the network protocols, the communication-to-computation ratio, the load balancing strategies, and the data partitioning schemes. The aim of this paper is to assess the strengths and limitations of a cluster of workstations by capturing the effects of the above issues. This has been achieved by evaluating the performance of this computing environment in the execution of a parallel ray tracing application through analytical modeling and extensive experimentation. We were successful in illustrating the effect of major factors on the performance and scalability of a cluster of workstations connected by an Ethernet network. Moreover, our analytical model was accurate enough to agree closely with the experimental results. Thus, we feel that such an investigation would be helpful in understanding the strengths and weaknesses of an Ethernet cluster of workstation in the execution of parallel applications. Keywords: parallel computing, ray tracing, networked workstations, performance evaluation 1