scholarly journals Ricochet of Spheres on Sand of Various Temperature

2018 ◽  
Vol 68 (2) ◽  
pp. 150 ◽  
Author(s):  
Yoon Keon Kim ◽  
Woo Chun Choi
Keyword(s):  
Shear Stress ◽  
Kinetic Energy ◽  
Internal Friction ◽  
Initial Conditions ◽  
Fem Analysis ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Depth Of Penetration ◽  
Safety Distance ◽  
Sand Temperature

The debris generated by the explosion of a building or ammunition is flown far away through the ricochet phenomenon. The debris contains a very large amount of energy, and a risk factor surrounding it may be applied. The safety distance from debris is set from experiments or FEM analysis. The ricochet of debris is affected not only by the initial conditions of the debris, but also by the conditions of the medium. In this paper, the effect of sand temperature on the ricochet of sphere projectiles was investigated through experiments and FEM, by measuring the shear stress and internal friction angle when the sand temperature increases. As the temperature of the sand increases, the shear stress and the internal friction angle decrease, and the penetration depth of the projectile increases. As the depth of penetration becomes longer, the kinetic energy is lost more by the friction force with the sand and, the sphere projectile speed decreases more. This is mainly caused by the energy loss of the projectile, so the kinetic energy of the ricocheted projectile is reduced. Therefore, when setting the optimized inhabited building distance (IBD), the conditions of the medium should be taken into account.

scholarly journals Ricochet of steel spheres on sand with varying water content

2020 ◽  
Vol 12 (12) ◽  
pp. 168781402097728
Author(s):  
Yoon Keon Kim ◽  
Woo Chun Choi
Keyword(s):  
Kinetic Energy ◽  
Internal Friction ◽  
Energy Loss ◽  
Water Content ◽  
Yield Stress ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Element Analysis ◽  
Lower Yield Stress ◽  
Safety Distance

The explosion of a building generates plenty of debris that flies far away. The flying debris is hazardous because it contains large amounts of kinetic energy. Therefore, determining the safety distance from the debris is essential. However, debris ricochet that collides onto the ground affects the safety distance because the ricochet phenomenon is influenced by the condition of the medium. In this study, experiments and finite element analysis were performed to investigate the ricochet based on the water content of sand. From a direct shear test, the internal friction angle and cohesion of sand were obtained based on the water content. The effects of internal friction angle and adhesion on the yield stress and ricochet were investigated. The results indicated that as the water content increased, the internal friction angle increased and then decreased, and the cohesion continued to decrease. The yield stress was proportional to the internal friction angle and inversely proportional to adhesion. Therefore, lower yield stress resulted in deeper penetration of debris, leading to higher energy loss, which increased the kinetic energy loss factor. Thus, the condition of the medium should be considered for setting a proper safety distance suitable for the surrounding environment of the building.

Characterization of Shear Strength and Interface Friction of Organic Soil

2020 ◽  
Vol 857 ◽  
pp. 203-211
Author(s):  
Majid Hamed ◽  
Waleed S. Sidik ◽  
Hanifi Canakci ◽  
Fatih Celik ◽  
Romel N. Georgees
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Internal Friction ◽  
Moisture Content ◽  
Water Content ◽  
Friction Angle ◽  
Structural Materials ◽  
Organic Soil ◽  
Internal Friction Angle ◽  
Interface Friction

This study was undertaken to investigate some specific problems that limit a safe design and construction of structures on problematic soils. An experimental study was carried out to examine the influence of loading rate and moisture content on shear strength of organic soil. Influece of moisture content on interface friction between organic soil and structural materials was also attempted. A commonly used soil in Iraq was prepared at varying moisture contents of 39%, 57% and 75%. The experimental results showed that the increase in water content will decrease the shear stress and the internal friction angle. An increase of the shearing rate was found to decrease the shear stress and internal friction angle for all percetanges of water contents. Further, direct shear tests were carried out to detect the interface shear stress behavior between organic soil and structural materials. The results revealed that the increase in water content was shown to have significant negetavie effects on the interface internal friction and angle shear strength.

scholarly journals Experimental Study on the Effects of Initial Shear Stress and Vibration Frequency on Dynamic Strength of Saturated Sands

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Jian Zhang ◽  
Jiuting Cao ◽  
Sijie Huang
Keyword(s):  
Shear Stress ◽  
Internal Friction ◽  
Vibration Frequency ◽  
Stress Ratio ◽  
Dynamic Strength ◽  
Friction Angle ◽  
Cyclic Stress ◽  
Internal Friction Angle ◽  
Shear Stresses ◽  
Cyclic Stress Ratio

The cyclic triaxial system is used to investigate the effects of confining pressure, initial shear stress, cyclic stress ratio, and vibration frequency on the dynamic strength characteristics of saturated sand in the Wenchuan area. Results show that when the vibration frequency is constant, the dynamic strength of sand increases with the increase of the consolidation ratio. However, when the consolidation ratio exceeds a certain value, the dynamic strength of sand decreases or increases slowly. The dynamic internal friction angle first increases and then decreases with the increase of consolidation ratio, and the dynamic internal friction angle under different initial shear stresses differs by a maximum of about 12%. When the failure cycles are constant, the dynamic strength and the dynamic internal friction angle of the sand increase with the increase of vibration frequency, and the dynamic internal friction angle at different frequencies differs by a maximum of about 7%. When the cyclic stress ratio is constant, the higher the vibration frequency, the greater the cycles required to achieve the failure. As the cyclic stress ratio decreases, the influence of the vibration frequency on the failure cycles is gradually reduced.

Effects of stress on failure behaviour of shallow-marine muds from the northern Gulf of Mexico

2018 ◽  
Vol 477 (1) ◽  
pp. 523-536 ◽  
Author(s):  
Brandon Dugan ◽  
Xin Zhao
Keyword(s):  
Shear Stress ◽  
Internal Friction ◽  
Gulf Of Mexico ◽  
Pore Pressure ◽  
Slope Failure ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Failure Behaviour ◽  
Northern Gulf Of Mexico ◽  
Peak Shear Stress

AbstractDirect simple shear experiments on mud samples from 0 to 15 mbsf (metres below seafloor) in the Ursa Basin (northern Gulf of Mexico) document that stress level impacts shear strength and pore pressure during failure. As burial depth increased (from 7.35 to 13.28 mbsf), cohesion decreased (from 12.3 to 6.5 kPa) and the internal friction angle increased (from 18° to 21°). For a specimen from 11.75 mbsf, an increase in maximum consolidation stress (from 45 to 179 kPa) resulted in an increase in the shear-induced pore pressure (from 29 to 150 kPa); however, the normalized peak shear stress decreased (from 0.37 to 0.25). Our results document that consolidation at shallow depths induces a positive feedback on pore-pressure genesis. For resedimented samples, which lack a stress history, cohesion was 3.6 kPa and the internal friction angle was 24°. As the maximum consolidation stress increased (from 40 to 254 kPa) on resedimented samples, the shear-induced pore pressure increased (from 22 to 203 kPa), whereas the normalized peak shear stress decreased (from 0.32 to 0.25). Our experiments showed that resedimented samples have similar strength and failure behaviour to intact samples. By constraining pore pressure, strength and initial stress state, we gain a better insight into slope-failure dynamics. Therefore, our experiments provide constraints on strength and shear-induced pore pressure at the onset of shallow failure that could be included in slope-failure and hazard models.

scholarly journals Improvement Methods for Reduction of the High Stress of Ultra-High Asphalt Concrete Core Dams

2019 ◽  
Vol 9 (21) ◽  
pp. 4618
Author(s):  
Jun Gao ◽  
Faning Dang ◽  
Zongyuan Ma ◽  
Yi Xue ◽  
Jie Ren
Keyword(s):  
Shear Stress ◽  
Internal Friction ◽  
Tensile Stress ◽  
Stress Level ◽  
Asphalt Concrete ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
High Shear ◽  
High Shear Stress ◽  
Concrete Core

With the rapid development of asphalt concrete core rockfill dams (ACCRDs), the construction of ultra-high asphalt concrete core rockfill dams (UACCRDs) has been improved significantly. However, the security problems of asphalt concrete core (ACC) become very prominent with the increase of dam height. The shear failure control standard and tensile failure control standard of ACC are suggested. The mechanisms of ACC that generate high shear stress and high tensile stress are investigated. Based on the definition of stress level and the transmission mechanism of arch structures, the improvement methods that reduce the high shear stress and high tensile stress of ultra-high asphalt concrete core (UACC) are proposed and investigated. The results show that the stress level of ACC can be reduced significantly by the increase of the strength parameters of ACC (failure ratio, cohesion, and internal friction angle). The following value ranges of the failure ratio, cohesion, and internal friction angle of ACC for the suitable construction of UACCRDs are recommended: Rf ≥ 0.75, C ≥ 0.30 MPa, and φ ≥ 28.5° (h = 150 m), with the growth gradient adjusted by 5%, 15%, and 5%/25 m. The tensile stress and tensile stress area can be reduced obviously by the new type of dams (curved asphalt concrete core rockfill dams (CACCRDs)). The value ranges of the curvature of CACC (k ≥ 1.0 × 10−3) for the suitable construction of UACCRDs are recommended.

scholarly journals Influence of Structural Plane Microscopic Parameters on Direct Shear Strength

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Yanhui Cheng ◽  
Weijun Yang ◽  
Dongliang He
Keyword(s):  
Particle Size ◽  
Shear Strength ◽  
Internal Friction ◽  
Direct Shear Test ◽  
Shear Test ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Direct Shear ◽  
Stiffness Ratio ◽  
Structural Plane

Structural plane is a key factor in controlling the stability of rock mass engineering. To study the influence of structural plane microscopic parameters on direct shear strength, this paper established the direct shear mechanical model of the structural plane by using the discrete element code PFC2D. From the mesoscopic perspective, the research on the direct shear test for structural plane has been conducted. The bonding strength and friction coefficient of the structural plane are investigated, and the effect of mesoscopic parameters on the shear mechanical behavior of the structural plane has been analyzed. The results show that the internal friction angle φ of the structural plane decreases with the increase of particle contact stiffness ratio. However, the change range of cohesion is small. The internal friction angle decreases first and then increases with the increase of parallel bond stiffness ratio. The influence of particle contact modulus EC on cohesion c is relatively small. The internal friction angle obtained by the direct shear test is larger than that obtained by the triaxial compression test. Parallel bond elastic modulus has a stronger impact on friction angle φ than that on cohesion c. Under the same normal stress conditions, the shear strength of the specimens increases with particle size. The shear strength of the specimen gradually decreases with the increase of the particle size ratio.

Stability Analysis of Dam Slope by Double Safety Factors of Dynamic Local Strength Reduction Method

2015 ◽  
Vol 744-746 ◽  
pp. 593-596
Author(s):  
Yuan Meng
Keyword(s):  
Internal Friction ◽  
Reduction Method ◽  
Failure Process ◽  
Friction Angle ◽  
Strength Reduction ◽  
Internal Friction Angle ◽  
Material Strength ◽  
Strength Reduction Method ◽  
Strength Parameters ◽  
Local Strength

When calculating the dam slope failure process, traditional strength reduction method doesn't consider the difference of decay rate between cohesion and internal friction angle and discount the strength parameters for all elements. This paper uses two different reduction factors for material strength parameters, slope cohesion and internal friction angle. Based on the yield approach index criterion, we change the reduction region in time and put forward a double safety factor of dynamic local strength reduction method for engineering analysis of dam slope stability.

scholarly journals Stabilization of Algerian Clayey Soils with Natural Pozzolana and Lime

2017 ◽  
Author(s):  
Khelifa Harichane ◽  
Mohamed Ghrici ◽  
Said Kenai
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Plasticity Index ◽  
Engineering Properties ◽  
High Plasticity ◽  
Expansive Clay ◽  
Clayey Soils ◽  
Natural Pozzolana

Cohesive soils with a high plasticity index present difficulties in construction operations because they usually contain expansive clay minerals. However, the engineering properties of soils can be improved by different techniques. The aim of this paper is to study the effect of using lime, natural pozzolana or a combination of both lime and natural pozzolana on plasticity, compaction and shear strength of two clayey soils classified as CH and CL according to the unified soil classification system (USCS). The obtained results indicated that for CH class clay soil, the plasticity index decreased significantly for samples stabilized with lime. On the other hand, for the soil classified as CL class clay, a high decrease in the plasticity index value was observed for samples stabilized with natural pozzolana compared to those stabilized with lime. Also, both the cohesion and internal friction angle in lime added samples were demonstrated to increase with time. The combination of lime and natural pozzolana exhibits a significant effect on the enhancement of both the cohesion and  internal friction angle at later stages. The lime-natural pozzolana combination appears to produce higher shear strength parameters than lime or natural pozzolana used alone.

scholarly journals Effect of Glutinous Rice Slurry on the Reinforcement of Silt in the Yellow River Basin by Microbially Induced Carbonate Precipitation (MICP): Mechanical Property and Microcosmic Structure

2021 ◽  
Vol 2021 ◽  
pp. 1-23
Author(s):  
Jianwei Yue ◽  
Limin Zhao ◽  
Baoxi Zhang ◽  
Qingmei Kong ◽  
Siyuan Wang ◽  
...  
Keyword(s):  
Internal Friction ◽  
Yellow River ◽  
Friction Angle ◽  
Yellow River Basin ◽  
Reinforced Soil ◽  
Internal Friction Angle ◽  
The Yellow River ◽  
Mass Ratio ◽  
Glutinous Rice ◽  
The Yellow River Basin

The silty clay in the lower reaches of the Yellow River is characterized by loose structure, low strength, and strong capillary effect. Based on the technology of ancient glutinous rice mortar and microbial-induced calcium carbonate precipitation (MICP), experiments on optimal mass ratio of cementitious liquid to bacterial liquid and optimal concentration of cementitious liquid for MICP and improved MICP technology were carried out by measuring the production of CaCO3, and direct shear test and unconfined compressive strength test of plain silt, glutinous mixing silt, and improved silt with MICP and modified MICP were conducted. The microstructure of the reaction products of MICP and improved MICP technology were also evaluated based on scanning electron microscopy (SEM). Research results showed that the mechanical properties of silt with glutinous rice slurry were effectively improved. With the increase in the concentration of glutinous rice slurry, the strength and internal friction angle of soil samples first increased and then decreased, and the cohesion presented a linear increasing trend. When the concentration of cementitious liquid was 0.5 M and the mass ratio of cementitious liquid to bacterial liquid was 2 : 1, the amount of CaCO3 formed was the most, and the conversion rate of Ca2+ was more than 80%. The improved MICP could increase the conversion rate of Ca2+ (93.44%). An improved MICP showed that glutinous rice slurry could improve bacterial activity, increase the urease content in the bacterial solution, and promote the production of CaCO3. Silt cohesion and internal friction angle of the silt were improved by the improved MICP technology, and the strengthening effect of mechanical properties of modified MICP-reinforced soil is better than that of the MICP-reinforced soil; conventional MICP technology could also improve the soil cohesion, but the improvement in the internal friction angle was not obvious. The SEM results indicated that compared with the reaction product of MICP technology, the structure of the product of improved MICP technology is more compact, resulting in a marked reinforcement of MICP performance with glutinous rice slurry. This study provides new insights into enhancing the mechanical behaviour of MICP-treated silt in the Yellow River Basin with glutinous rice slurry.

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