Discontinuities usually rule the mechanical behavior of a rock mass. The free surface of geotechnical structures such as dam foundations, powerhouses, slopes, and tunnel walls, are also significantly affected by discontinuities. Besides, when the intact material is relatively strong, the effect of discontinuities and their properties would even increase. The direct shear test is a well-known test for determining the shear strength of saw-cut surfaces and natural joints of rocks, which provide the most valuable results for engineering design parameters. The shear strength of concrete layers in Rolling Compacted Concrete dams (RCC dams) is also considered a crucial engineering design parameter. This parameter is additionally determined by direct shear testing on the cored samples of a dam body. The in-situ direct shear test is the most precise direct shear test, among other direct shear test types. However, due to the enormous costs and difficult executive operations of the in-situ direct shear test at sites, the direct shear test would be conducted in the laboratory most of the time. The laboratory direct shear test could be conducted at small and Large scales. In case that the subjected project has great importance, by using the Large scale laboratory direct shear test, more precise results would be acquired. For this purpose, the Azmouneh Foulad Consultant Engineers Co. has designed and manufactured a Large scale direct shear box that can be used for more accurate simulation of the in-situ direct shear test. This shear box, which is unique in its category, is capable of 35×35 cm samples testing.

Reinforcement of ballast with the help of Geogrids is one of the methods that have been studied by various researchers in the technical literature to increase the load capacity as well as reduce the deterioration of the ballast through the reduction of crushing and settlement. In this article, by introducing a new type of geogrids made with the help of waste rubber belts called Geo-scrape, their effect on the shear behavior of ballast in a Large-scale shear test has been investigated. In this direction and in order to investigate the effect of the dimensions of the geo-scrap on the ballast shear behavior and by placing the geo-scrap with the dimensions of 5x5, 10x10 and 25x25 cm square in the upper layer, various tests were carried out under vertical loads of 50, 100 and 150 Kilopascal has been done and the results are presented in the form of shear stress-horizontal displacement curve, maximum shear strength, internal friction angle and dilatancy angle. The summary of the results shows that the mesh of 5x5 cm2 has provided the most favorable conditions for the ballast in terms of increasing the shear strength, increasing the internal friction angle and decreasing the dilatancy angle. So that by placing the geo-scrape with the dimensions the mesh of 5x5 cm2, the shear strength, internal friction angle and dilatancy angle are increased by 20%, 7% and 30% respectively compared to the unreinforced state.

The goal of this research is to measure the interface properties between a geogrid and a soil (i.e. the friction angle and dilatancy angle) as well as the strength parameters of materials used in the tests in order to be able to use the parameters in numerical analysis. A comprehensive set of Large shear box tests were conducted on the geogrid. Apart from the main findings, some interesting results concerning the mechanisms behind the behaviour of reinforcement in direct shear tests were obtained.

1. Introduction: Soil nailing is regarded as one of the cast-in-place reinforcement methods for soil slopes to limit the deformation and increase its safety the use of which is considerably increasing due to some advantages such as short-term construction and low-cost implementation. This method is commonly used in compact and dense soils, as well as slopes where heavy machinery is difficult to access, although its use is limited in loose soils. The reason for using this method in dense soil is that the fine particles are less in this type of soil and have poor cementation, which itself causes little adhesion in the soil. In addition, a proper interaction results from the friction between the soil and the nail wall in this soil...

In this paper a laboratory study has been carried out on the effect of changing the type of soil filling cylindrical reinforcing elements from SM to GM on behavior of sandy soil. In this study the primary tests for evaluation of the impact of reinforced sand and gravel columns with diameters of 5 cm and heights of 15 cm subjected to vertical stresses of 50, 100, and 150 KPa were carried out in a Large-scale direct shear apparatus (300×300×150 mm). Results showed that the shear stress and settlement of the reinforced sample with geogrid and a gravel column increases by 45.4% and decreases by 23.9% respectively compared to the non-reinforced sample.

In this paper, the effects of the atmospheric boundary layer as well as the inflow turbulence on the performance of a Large-scale wind turbine are investigated. The reference wind turbine is the NREL 5 megawatts with a rotor diameter of 126 meters. Wind shear modeling is carried out using the mixing length theory. Due to the importance of turbulence analysis, the Sandia method is applied. According to the reference level, the roughness coefficients of 0. 01, 0. 2 and 0. 5 and disturbances in the roughness of 0. 5 with the intensity of 1, 5 and 15 percent are studied. The aerodynamic forces of the rotor are calculated based on the modified blade element momentum theory. The results show that in the case of maximum roughness the averaged output power is reduced to 160 kW. Moreover, at 15% turbulence intensity, 50 kN and 25 kN are added to the maximum/minimum thrust force value, respectively.

This study investigates the deformation behavior of layered sedimentary rocks with diverse geotechnical properties under Large-scale lateral loading conditions. These loads, primarily induced by tectonic activities, significantly alter the stress-strain distribution in geotechnical structures such as tunnels and roads built on slopes. Understanding these deformations is crucial for assessing the stability and performance of such structures. To analyze these effects, a series of controlled laboratory experiments were conducted using a specialized testing device designed to simulate lateral loading scenarios. The device measures layer deformations in meganeutons per square meter, providing precise insights into the mechanical response of bedded rock formations. The experimental setup involved systematically applying varying lateral loads while monitoring deformation patterns in different sedimentary rock samples. The recorded results highlight how weak sedimentary rocks respond to stress redistribution and lateral forces. The findings reveal critical deformation trends, structural weaknesses, and failure mechanisms that influence the long-term stability of geotechnical structures. This research contributes to a better understanding of the lateral load effects on layered rock formations and provides valuable data for designing more resilient infrastructure in geologically active regions.

Aim of this study is to measure shear stress in smooth rectangular and trapezoidal open channels. A new approach is presented to measure direct shear on wet perimeter of open channels. A water flume with a section on a frictionless support (called knife edge flume) along with a system of load cell was used to measure total force on the wet perimeter. The local boundary shear stress in rectangular and trapezoidal cross sections was measured using a 4mm diameter Preston tube connected to a differential pressure transducer and a data acquisition system. The calibration curves proposed by Patel were used to convert the pressure readings to shear stress. Local and total shear measurements were used to differentiate the channel wall and bed shear forces. This method allows minimizing of the error as result of the Preston tube diameter. Comparison of the results confirmed advantage of the momentum method over the energy method in term of accuracy. Results are presented for smooth rectangular and trapezoidal channel cross sections with side slopes of 1, 1.5, and 2.

Due to the increasing production of plastic materials, there is an international concern about disposal or recycling of plastic waste in the world. One of the ways to reuse plastic waste is to use it in the engineering works to modify mechanical properties of loose soils. The purpose of this research is to find a way to reuse a particular kind of plastics (bottles of dough, soft drinks, mineral water, etc. ) in geotechnical works to improve soil. In this paper, the mechanical behavior of Anzali Port sand, reinforced with 1×1 cm polyethylene terephthalate crumbs and 1×5cm strips, to 0, 0. 1, 0. 5, 1 and 2% and polyethylene terephthalate fibers to 0 and 0. 1 and 0. 5% of the dry weight of the soil which were arranged separately, was evaluated. Samples were prepared at the relative density of 75%. The effects of parameters such as dimensions, the weight percentage of reinforcers in the soil and vertical stress were investigated. The results of the experiments showed that although the polyethylene terephthalate crumbs and strips improve the mechanical behavior of sandy soil, but the effect of fiber reinforcers on soil mechanical properties has been much higher. Also, the optimum percentage of polyethylene terephthalate crumbs and strips reinforcers was 1% of sand dry weight. The comparison between reinforced and unreinforced samples showed that reinforced specimens had more ductility and resistance.