In this paper we investigate the mechanism of INTERNAL EROSION caused in the right abutment of the Shahghasem dam’s spillway. Shahghasem dam is an earthen dam located in Yasouj, in southwest of Iran. A significant hole and pipe have been observed in the corner of the right abutment from upstream view. The foundation is Marlstone, which has low cohesion and susceptible for INTERNAL EROSION and piping in some conditions. Going through details of the design maps has shown that Lane’s criteria for selecting safe dimensions of the seepage control measures have not been considered properly. A series of the supportive walls are designed to attach to the right part of the spillway in order to increase the length of seepage. The pipe route of the EROSION should also be grouted with high quality concrete.

INTERNAL EROSION is a common reason for dam failure, which is caused by soil subsidence and the formation of sinkholes. This phenomenon typically occurs in INTERNALly unstable soils. The dam is located in Neyshabour City and is built on a deep alluvial foundation with gap-graded and concave gradation soils. This study aims to investigate the potential for soil suffusion and the impact of compaction and surcharge on INTERNAL EROSION. Initially, Data was collected after the dam impounding, index tests were conducted on soil samples. Subsequently, three methods were used to assess the probability of suffusion based on the particle size distribution and experimental criteria. Two methods indicated soil was INTERNALly unstable, while one method indicated stability. To study the influence of compaction. Soil samples were tested at different densities under four water head conditions. The results indicated that the soil has the potential for suffusion and is INTERNALly unstable. Furthermore, the study found that compaction reduced soil EROSION, with the amount of washed fine particles decreasing from 4.5% at 70% relative density to 0.37% at 85% density. Moreover, increasing compaction from 70% to 85% resulted in a deformation decrease from 13.3% to 3.33%.

Owing to the fact that the world's population and their need for water are becoming increasingly larger, the construction of structures like dams and levees to profit from water sources and, also, the prevention of possible disasters, are inevitable. Moreover, embankments are more economical and have been immensely under consideration by the expert communities. INTERNAL EROSION plays a major role in the failure of embankments. Due to INTERNAL EROSION of an earth dam water that seeps through the dam, soil particles are carried away from the embankment, foundation, or abutments of the dam. INTERNAL EROSION may be a result of inadequate compaction during construction, differential settlement, desiccation, earthquakes, burrowing animals, and/or vegetation roots. The erodibility of the material in the INTERNAL EROSION flow path and hydraulic stresses are the most important factors in determining the degree of EROSION. The challenge in predicting failure due to INTERNAL EROSION characterizes the material properties relevant to the rate of failure. To prohibit this natural phenomenon, the addion of chemical additives and grouting is highly suggested. In the present study nanoclay devoid of any environmental detrimental effects was utilized. Erodibility of samples contained naoclay with 0, 1 and 1. 5 weight percent of dry soil and curing time of 0, 7, 14, 28 days went under investigation through image processing. Furthermore, to make a contrast between the modern and typical additives, another sample containing bentonite clay with 5 weight percent of dry soil was used. The results illustrated that the specimen containing 1 weight percent of nanoclay with a curing time of 14 days possessed the strongest resistance. Curing time of 14 days diminished erodibility in all the specimens; however, the allocation of more curing time had no beneficial effect. In addition, the sample containing 5 wt. % bentonite clay could decrease erodibility to a 10-fold extent, compared to the sample containing 1wt.

The two most common causes of embankment failure are embankment overtopping and INTERNAL EROSION. INTERNAL EROSION of soil resulting from seepage flow is the main cause of serious hydraulic structures (dykes, dams) failure, in terms of the risk of flooding areas located downstream. The EROSION characteristics are described by the EROSION Rate Index, which measures the increase in EROSION rate with respect to an increase in the hydraulic shear stress; and the Initial Shear Stress, which represents the minimum hydraulic shear stress when EROSION starts. The EROSION Rate Index ranges from 0 to 6, indicating that the changes in EROSION rates in response to changes in hydraulic shear stress can differ by up to 106 times across different soils. Coarse-grained, noncohesive soils, in general, erode more rapidly and have lower Initial Shear Stresses than fine-grained soils. The challenge in predicting failure due to INTERNAL EROSION is characterizing the material properties relevant to the rate of failure. Therefore, it is very important to improve the EROSION resistance of soils using appropriate and cost effective techniques. In order to control INTERNAL EROSION and treat erodible soil, the important point is to use modern stabilizers instead of traditional ones which are harmful. In this study, polyvinyl acetate polymer material has been used as a treatment for the erodibility of kaolinity clay sand. To conduct this research, kaolinity clay sand has been treated with different percentages of polyvinyl acetate polymer and it has been tested with hole EROSION apparatus in different hydraulic gradients. The hole EROSION test (HET) is one of several available procedures for characterizing the erodibility of cohesive soils that might be susceptible to INTERNAL EROSION, in dams and levees. It was first developed in a constant-flow configuration (Lefebvre et al. 1984) and more recently in a constant-head configuration by Wan and Fell (2004). The HET utilizes an INTERNAL flow through a hole pre-drilled in the specimen, a flow condition similar to that occurring during piping EROSION of embankment dams. In the constant-head configuration, the test head is typically doubled, starting from 50 mm, until progressive EROSION of the pre-drilled hole is produced. Measurements of accelerating flow rate through an eroding pre-drilled hole in a test specimen yield estimates of the critical shear stress and EROSION rate coefficient. The initial and final eroded hole diameters are used to compute initial and final friction factors, and intermediate hole diameters are then computed according to the flow rates measured during the course of the test. Result showed that the EROSION rate of kaolinity clay sand is extremely rapid and polyvinyl acetate polymer stabilizer increased the resistance of kaolinity clay sand to EROSION. It was also found out that with the addition of polyvinyl acetate polymer, the EROSION type changes from extremely rapid to moderately slow. Adding polyvinyl acetate polymer caused the unconfined compression strength of kaolinity clay sand to increase by 60%.

Sound is one of the forms of mechanical energy and the two main characteristics of sound are intensity or power and frequency or wavelength of sound.their performance against the incoming sound wave, industrial silencers can be divided into two general groups of resonating and absorption silencers, the main difference between these silencers is the release of sound energy from the channeling system, which is one of the common examples of the use of resonating type silencers, their use in It is the INTERNAL combustion engines that distinguish absorption silencers from the resonator type based on the fact that the main and visible part of the act of muting the sound is achieved by changing sound energy to heat energy.The goal of this article is to design a muffler based on the breaking of sound frequencies resulting from the movement of fluid in the exhaust output of vehicles, which leads to a reduction of at least 50 db of sound and gives the operator enough peace and concentration. In this article, after examining three types of mufflers, absorbent mufflers that use the properties of porous absorbent material to absorb passing sound and are the simplest form of mufflers, have been selected, analyzed and reviewed and are suitable for the OM457 engine of Idem Industrial Company. It designed for maximum inlet exhaust temperature is 520 and for the maximum kW power is 315 with the maximum discharge relative pressure of 185 mbar for homogenization with the standard atmosphere.

INTERNAL EROSION refers to the seepage-induced movement of a fraction of soil particles in such a way that the initial state of the soil structure changes. Accordingly, severity and mechanism of the particle movement depend upon the geometric, mechanical, and hydraulic conditions, which is of a higher probability in the case of concave upward and gap-graded soils. INTERNAL EROSION is one of the long-lasting challenges in the design of earth dams and engineering fills to which considerable attention has been given. To date, extensive studies have been conducted on the four regular types of INTERNAL EROSION such as concentrated leak EROSION, contact EROSION, backward EROSION, and suffusion; subsequently, various techniques and criteria have been proposed for identification and assessment of this phenomenon. Hence, the previous studies are mainly focused on the geometric parameters (e. g., gradation, void ratio, etc. ), whereas the mechanical and hydraulic factors have gained less attention. However, most of the studies and experimental apparatuses for evaluating the occurrence of these phenomena in susceptible soils have been in terms of one-dimensional (upward or downward) flow applied perpendicular to the soil layers. There is also no mention of the effect of flow direction and direction of the layers in the existing criteria for evaluating INTERNAL stability, whereas natural deposits and even engineering fills are not necessarily perpendicular to the direction of the layers. Also, flow direction towards gravity is not necessarily zero or 180 degrees and may be present in any case Therefore, in this study, a special physical model was designed and developed to study samples of gravel size and different directions of layers and inflow. The results of experiments carried out on gap-graded soils show that the critical gradients are more in soils with perpendicular layers than those with parallel layers. Also, as the angle of flow relative to the direction of gravity increases, the critical gradients generally increase; in addition, the direction of the layers relative to the inlet flow to the soil specimen completely affects the shape of eroded pipes in the soil.

The phenomenon of INTERNAL EROSION in embankment dams is one of the threats to their stability and the presence of Dispersive Clayey soils on the embankment dam is one of the exacerbating and one of the reasons that causes INTERNAL EROSION which is associated with dam damages. Basically, Dispersive Clayey Soils in the vicinity of moisture and saturation will highly lose resistance Due to the presence of Na+. Due to the mentioned fact, stabilization of these soils seems to be of essential importance for the sake of making proper embankment of hydraulic projects. One way for soil amendment and confronting soil EROSION is the injection of additives. In this research, nanoclay (montmorillonite) has been used as a modern and eco-friendly additives for controlling INTERNAL EROSION in Dispersive soils. nanoclay materials had particle size ranges of 1– 2 nm and specific surface area value of 220– 270 m2/g. The dispersion ratio of soil was equal to 86%. In order to investigate the erodibility values, samples containing 0, 0. 5, 1, 1. 5 and 3 (weight percent) of dry soil were tested by Hole EROSION Test. After determining the optimal percentage of nanoclays, effects of hydraulic gradient (i= 7. 05, 7. 96, 11. 05) and processing time (t= 1, 2, 7, 14, 28 day) on erodibility of samples containing the optimum amount of nanoclays and also the effect of optimal amount of nanoclays on atterberg limits of soil were investigated. Experiment results on Dispersive Clayey Soils without nanoclay showed that the index of EROSION rate of soil was in the fairly fast group. The results show that adding nanoclay to soil increases the index of EROSION rate and decreases soil erodibility. So that the EROSION of the soil changes from fairly fast group in the control soil to laminar group. At the processing time of 1 day, the optimum amount of nanoclay in reducing EROSION was obtained 1% and the index of EROSION rate was 4. 33. The optimum amount of nanoclay in the processing times of 2 and 7 days was observed equal to 1. 5% and the index of EROSION rate was 4. 85 and 4. 72, respectively. It was also observed that in larger hydraulic gradients, the effect of nanoclay in reducing EROSION is more. In addition for optimal amount of nanoclays with increasing hydraulic gradient and processing time, the index of EROSION rate increased and sample’ s erodibility decreased. So that, in the hydraulic gradient equal to 11. 05, the index of EROSION rate increased by 5%. Also the index of EROSION rate has increased with increasing processing time. So, at the processing time of 28 days, the amount of increasing in the index of EROSION rate in hydraulic gradients equal to 11. 05, 7. 96 and 7. 06, is 23. 8%, 23. 4% and 20. 3%, to the control soil, respectively. Also adding the optimum amount of nanoclays because of absorbing water, has expands atterberg limits of soil. So that with adding 1 percent nanoclays increased liquid limit (about 4 percent), plastic limit (about 4. 2 percent) and plastic index (about 3 percent) of dispersive clayey soil and adding 2 percent nanoclays decreased atterberg limits of soil, compared to the control sample.

INTERNAL EROSION and scouring have always created many problems for earth dams. Since half of the world's earth dams damages result from INTERNAL EROSION, this process has been recognized as the second reason for the fracture of these dams and has raised major concerns. Although there have been many proven methods to control this phenomenon for over 50 years, this problem has not yet been completely resolved. It includes different processes such as piping and suffusion. The study of these phenomena is an important topic in many different fields such as hydraulic and geotechnical engineering. One of the ways to alleviate this phenomenon is soil remediation, which requires adding different percentages of additives to the soil. Since these additives may damage the environment or cost a lot, we need to find optimum quantities that reduce cost and environmental problems. In this study two additive substances like cement and nanoclay were added to the soil and according to research, cement and nanoclay were not environmentally and economically suitable in large volumes, respectively. In the present study, low percentages of these materials were used and the Hole EROSION Test (HET) was run to control the phenomenon of INTERNAL EROSION. Given that the soil used in this study was silty sand, we added 0. 25, 0. 5, 1, 2, and 3 percent cement and 0. 5, 1 and 1. 5 percent nanoclay to the soil and after passing the curing time (1, 7, 14, and 28 days), the soil was compressed by the compression hammer and tested. According to the results after 28 days, the EROSION rate index increased more than threefold in 1. 5% nanoclay and 1% cement compared to the control soil, which changed the soil group from relatively fast to very slow and leads to the reduction of erodibility. Moreover, at all the percentages and intervals, critical shear stress of soil samples with cement was higher than that of nanoclay.

Purpose: To compare the anatomical and functional results of deep vitrectomy with and without ILM peeling for full thickness macular hole.Materials & Methods: 37 eyes of 37 patients with full thickness macular hole (FTMH), confirmed by clinical examination and optical coherence tomography (OCT), enrolled in this clinical trial. Based on the stage of FTMH (stage 2, 3, 4) as described by Gass and the techniques of surgery (with or without ILM peeling) the patients were randomized into two different groups. All patients underwent preoperative Act and at least one OCT image was obtained during the postoperative follow up.After obtaining informed consent, deep vitrectomy and 20% SF6 injection was performed. The patients were unaware of their allocation status. Patients data & surgical outcome were collected and statistically analyzed. Anatomical success was defined as hole closure at postoperative OCT and functional success was referred to any improvement in visual acuity. Macular hole index (MHI) was defined as a ratio of the greatest height to the base diameter of the hole on cross-sectional OCT images.Results: 37 eyes of 37 patients (15 men & 22 women) were enrolled. The mean age of the patients was 56.4±21.94 years and FTMH were traumatic in 13 cases (35%) and Idiopathic in 24 (65%) cases. Twenty cases underwent deep vitrectomy with ILM peeling (ILM group) and the remaining cases underwent vitrectomy without ILM peeling (no ILM group).The mean preoperative 10gMAR visual acuity was 1.38±1 in the ILM group and 1.22±0.13 in the no ILM group, these improved to 0.95±1 and 0.77±0.31 postoperatively in the ILM and no ILM group, respectively (P=0.871). The overall anatomical success rate was 64%. The hole was closed in 70% of ILM peeling and 47% in the no ILM group (Chi-square test, P=0.15). In anatomically successful cases the mean of postoperative VA was significantly improved (P=0.001).In traumatic subgroup, ILM peeling seems did not affect the anatomical (P=0.2) and visual Success rates (P=0.5). There was no significant differences in hole closure rates between the traumatic and idiopathic FTMH (P=0.968). Visual acuity significantly improved after operation In MHI ³ 0.5 group compared with the MHk 0.5 group. The stage of the hole did not affect the anatomical success rate (P=0.52) or visual acuity improvement (P=0.741). Macular hole index ³ 0.5 had a prognostic value for postoperative visual acuity improvement. The hole duration was not related to anatomical success rate but there is an inverse relation between duration of the symptoms and improvement in VA.Conclusion: Deep vitrectomy and SF6 injection was a safe & effective surgical technique for full thickness macular hole and peeling of the ILM seems did not affect the anatomical or functional success rates. The hole duration, stage and origin of the hole (traumatic or idiopathic) does not related to the anatomical success or visual acuity improvement. MHI  ³ 0.5 seems to be a prognostic factor for postoperative visual improvement but not for closure rate.