Ratio Of Gravel Research Articles

Research on the effect of sand content on stress and durability of cement

With the progress of science and technology and the improvement of people’s quality of life, the demand for materials is getting higher and higher. As one of the most important civil engineering materials, concrete is widely used to repair a large number of broken infrastructures. Its production uses sand and aggregate from quarrying operation. If the use is unreasonable, a large amount of waste will be produced. In addition, there is a significant shortage of natural building raw materials in many regions (especially in developed regions). So improving the sustainability and durability of concrete materials can save transportation costs. This paper mainly discusses the influence of sand content in cement concrete on the performance of the material itself. The maximum pressure resistance of the corresponding specimen is measured by the pressure sensor and other experimental instruments, and compared with the specimen of different shape and volume under the condition of different sand rate. By changing the ambient temperature, the number of times that the specimen does not conform to the specified standard value is measured, and the durability of the specimen with different sand ratio is obtained. In this work, the optimal sand gravel ratio is successfully and relatively accurately measured. And it can be reasonably used in infrastructure construction.

Spatial pattern of hydrological and erosion behaviour along a dolomite hillslope in Southwest China

Dolomite hillslopes are highly vulnerable to rocky desertification, but the linkages among soil type, runoff mechanisms, and soil erosion remain unclear. During four hydrological years (2018–2021), soil type, plot-scale hydrological and erosion behavior at the upper, middle, and lower slopes along the dolomite hillslope in karst regions of Southwest China were investigated. The results indicated that along the downward slope direction, the degree of soil development gradually increased, forming a typical soil catena pattern. The soil types along the downward direction on the dolomite hillslope gradually transitioned from Entisol to Inceptisol and to Semi-Alfisol. The Entisol was thin and gravelly, with the highest volume ratio of gravel of 75 %. In contrast, Semi-Alfisol was thick and clayey, with the highest volume ratio of fine soil of 97 %. The surface runoff coefficient of the upper slope was only 2.3 % because of the high water infiltration capacity of shallow and rocky soil, and the runoff generation mode was dominated by discontinuous infiltration–excess runoff occurring on rock outcrop patches. Due to the higher soil water content (mean value of 37 %) and frequently occurring lateral flow, the lower slope exhibited the highest surface runoff coefficient of 21 %, mainly as saturation-excess runoff. Catenary soils and their correspondingly divergent hydrological regimes led to average annual soil losses of 0.4, 0.8, and 2.8 t·ha−1·yr−1 at the upper, middle, and lower slopes, respectively. These results advance the understanding of the relationship between hydrology and erosion on karst hillslopes and provide theoretical support for further rocky desertification control.

Vibration characteristics of mineral composite beams by experimental modal test method

Abstract Some machines, such as heavy presses and rammers, can be exposed to big shock and inertial forces under dynamic severe working conditions. Even if vibration isolation to the foundations of machines operating under dynamic loads is applied, the exposure of these machines to shock and resonance loads may not be adequately prevented. The sensitivity of these machines, the product quality, or life span can also incredibly decrease. Therefore, it is essential to know the vibration behaviors of machine bodies and parts. This study investigates vibration characteristics of polymer matrix composite (PMC) materials by the experimental modal test method. Nine different composite beam samples having sizes of 20 × 25 × 480 mm were produced for modal tests. Composite beams contain different ratios of aggregate and epoxy resin. Each composite beam’s natural frequencies and damping ratios were defined with frequency response and coherence functions taken from the experimental modal tests. The results from the modal analysis revealed that the most influential parameter on the vibration properties was the gravel ratio. As a result of the experimental study, it was concluded that while epoxy-resin, gravel and fine-sand additives increased the stiffness of PMC beam, gravel and fine sand additives also increased the damping rate of PMC beam.

Analysis of the effect of fines content and loading frequency on the shear modulus and damping ratio of gravels

Analysis of the effect of fines content and loading frequency on the shear modulus and damping ratio of gravels

Stormwater Gravel-Peat Infiltration Filter – An Ecohydrological Technology with Good Urban Design

Urban stormwater flooding and pollution are severe issues due to connected impervious surfaces. Over recent decades, solutions to these issues have been towards stormwater source control measures. We developed an innovative cost-efficient stormwater infiltration filter, made of gravel-peat mixture and geotextile. Laboratory column tests were conducted to compare a range of volumetric ratios of gravel (limestone and silica) to peat regarding their heavy metal removal efficiency (RE). The tested heavy metals were cadmium, lead and zinc. All ratios had a high RE (95.9%-100%), despite very high initial metal concentrations. The 5LG:1P mixture (i.e., volumetric ratio of limestone gravel to peat was 5:1) had the highest RE (99.6%-100%) and is suggested as a good candidate for implementation. If a longer-term use is required, a 5SG:10LG:3P mixture (i.e., volumetric ratio of silica gravel, limestone gravel, and peat of 5:10:3) is recommended as it kept the high heavy metal RE with a lower clogging potential and lower cost than the 5LG:1P mixture. The most convenient but expensive filter material with high RE is limestone gravel alone. Finally, we proposed two field designs for implementing the infiltration filter, which incorporate concepts of “treatment train” and “good urban design”. We also provided some suggestions for the installation of gravel-peat infiltration filters.

An Experimental Study on the Shear Characteristics of Typical Colluvial Soil with Gravel and the Stability of Slopes in Wenzhou, China

Slope disasters are an important area of concern in the prevention and mitigation of national land disasters. To study the stability of the slope in Wenzhou, China, the basic physical and mechanical properties of undisturbed soil in this area were obtained from laboratory experiments of typical colluvial soil. From experimental results, it was determined that the soil was low-liquid limit clay containing gravel. The shear characteristics of soil for different water content, gravel ratios, and burial depth were also obtained from large-scale indoor direct shear tests. The test results show that: (1) for colluvial soil without gravel, increasing water content increases cohesion, but decreases internal friction angle; (2) for colluvial soil containing gravel, the shear stress drops sharply when the shear displacement is close to approximately 15 mm; (3) for the same gravel ratio, the contribution of the gravel to the shear strength of the shear surface is not significant at lower vertical stresses, but increases at higher vertical stresses. A finite element strength reduction method has been used to numerically simulate the typical binary slope in Wenzhou. The simulation results show that the factor of safety of the binary slope is dependent on the strength of the overlying soil. The variations of the safety factor with water content and the gravel ratio are consistent with the variations of shear strength with the water content and the gravel ratio obtained from the tests. Simultaneously, the soil–rock interface strength needs to be addressed in the analysis of binary slopes.

Characterization of the Dynamic Properties of Clay–Gravel Mixtures at Low Strain Level

In order to support the dynamic design of subgrade filling engineering, an experiment on the dynamic shear modulus (G) and damping ratio (D) of clay–gravel mixtures (CGMs) was carried out. Forty-two groups of resonant column tests were conducted to explore the effects of gravel content (0%, 10%, 20%, 30%, 40%, 50%, and 60%, which was the mass ratio of gravel to clay), gravel shape (round and angular gravels), and confining pressure (100, 200, and 300 kPa) on the dynamic shear modulus, and damping ratio of CGMs under the same compacting power. The test results showed that, with the increase of gravel content, the maximum dynamic shear modulus of CGMs increases, the referent shear strain increases linearly, and the minimum and maximum damping ratios decrease gradually. In CGMs with round gravels, the maximum dynamic shear modulus and the maximum damping ratio are greater, and the referent shear strain and the minimum damping ratio are smaller, compared to those with angular gravels. With the increase of confining pressure, the maximum dynamic shear modulus and the referent shear strain increase nonlinearly, while the minimum and maximum damping ratios decrease nonlinearly. The predicting equation for the dynamic shear modulus and the damping ratio of CGMs when considering confining pressure, gravel content, and shape was established. The results of this research may put forward a solid foundation for engineering design considering low-strain-level mechanical performance.

Experimental study on sand production characteristics in natural gas hydrate deposits

During the process of natural gas hydrate exploitation, the cementation state of the stratum changes due to the decomposition of skeleton hydrate. Fine sand in the reservoir will migrate to the wellbore with the fluid, which is the so-called sand production phenomenon. Sand production will bring great harm to hydrate exploitation. In this paper, a set of visualized sand production simulator was designed to obtain the factors influencing the sand production characteristics in different working conditions. It is found that fine sand will invade and block the gravel layer and it is accompanied by the subsidence of the sand layer. Fluid flow rate and initial hydrate saturation are important factors affecting the characteristics of sand production. In addition, it is of certain guiding significance to select the appropriate median diameter ratio of gravel to sand for sand control in the actual exploitation process.

한강 수변구역 복원지의 표토 특성 및 유기탄소 저장량 추정

This study was carried out to investigate and analyze the environmental characteristics of restoration areas in the riparian zones of the Han River, and to quantify the amount of topsoil organic carbon storage. As a result of investigation and analysis of 21 survey sites, the total number of species planted was found to be 17, and the mean number of species was 2.86±0.13 species per site. At least one species and a maximum of 7 species were planted at each site. The mean diameter at breast height was 9.1±0.6cm, the mean height was 6.2±0.3m and the root content in soil was 0.13±0.18 g/cm². As a result of the analysis of the soil characteristics, 6 out of 21 items, such as the bulk density, solid ratio, gravel ratio, soil hardness, sand content, and pH increased as the soil layer deepened. The topsoil organic carbon storage by layer was 11.54±1.08 ton/ha at 0-10cm, 8.69±0.81 ton/ha at 10-20cm, 7.97±0.79 ton/ha at 20-30cm, and the total from 0 to 30cm was 28.21±7.31 ton/ha. The highest amount of topsoil organic carbon storage by land use in the past was 35.17±5.31 ton/ha in agricultural lands, followed by 28.16±8.31ton/ha in residential areas, 21.87±9.05 ton/ha in commercial areas, 19.23±12.48 ton/ha in industrial areas, and 17.07±11.33 ton/ha in the barren areas. The highest amount of topsoil organic carbon storage in the restored areas was 38.46±3.14 ton/ha in 2006, followed by 28.57±7.84 ton/ha in 2016, and 16.78±6.06 ton/ha in 2011. The results of this study are expected to provide a basic database and evaluation criteria for enhancing the carbon abatement effects of the restoration sites in riparian zones in the future.

Palaeo-tsunami inundation distances deduced from roundness of gravel particles in tsunami deposits

Information on palaeo-tsunami magnitude is scientifically and socially essential to mitigate tsunami risk. However, estimating palaeo-tsunami parameters (e.g., inundation distance) from sediments is not simple because tsunami deposits reflect complex transport processes. Here, we show a new approach to estimate tsunami inundation distance based on the mixture ratio of gravels from several sources in tsunami deposits. We measured the roundness of source gravels in modern beach and fluvial deposits in a coastal valley in Japan through image analysis and then calculated the mixture ratio of both sediment types in tsunami deposits. Normalising the mixture ratios by inundation distances revealed an abrupt change in the mixture ratio at a constant percentile, regardless of tsunami magnitude. This relation allowed estimation of the inundation distance of palaeo-tsunamis during the last 4000 years.

A study on the characteristics and microstructures of GGBS/FA based geopolymer paste and concrete

Abstract The purpose of this study is to focus on the durability of geopolymer concrete after nine months of an indoor and outdoor curing period. The geopolymer paste was prepared with fly ash and ground granulated blast furnace slag as raw materials and sodium silicate/sodium aluminate as an alkali activator. The geopolymer concrete was prepared with a 1:2.5:2.4 geopolymer:sand:gravel ratio. The influence of sodium aluminate, wollastonite additions and NaOH concentration on the microstructure, physical and mechanical properties were evaluated. The compressive strength of the geopolymer concrete can reach 67 MPa and 53 MPa after 180 days of indoor and outdoor curing, respectively. Rapid Chloride Ion Permeability Test (RCPT) shows the geopolymer concrete has excellent chloride resistance over prolonged curing time. After 180 days of accelerated wetting-drying cycles, the continued growth of compressive strength indicates the good weathering resistance of geopolymer concrete. According to the test results obtained during this study, the geopolymer has a high potential to be a key material for civil construction.

Evaluation of physical erosivity factor for interrill erosion on steep vegetated hillslopes

The process of interrill erosion is complex by interaction of raindrop impact and sheet flow. Their relative contribution to interrill erosion is difficult to be evaluated even on bare soil. This study presents the new erosivity factor to evaluate the interrill erosion on steep vegetated hillslope with the more relevant understanding of the physical processes. The effective energy, the erosivity factor, is defined as the sum of the effective kinetic energy of rainfall and effective potential energy of surface runoff based on the energy balance. The effective kinetic energy of rainfall is determined by the horizontal component for slope of kinetic energy deducting energies dissipated by structure of vegetation canopies and a litter layer. The effective potential energy of surface runoff is equal to potential energy of the available surface water following rain-mass allocations of interception and infiltration. The data from experimental field plots with various vegetation coverage after wildfire were used to verify the effective energy equation. On densely vegetated slopes sediment yield depended greatly on effective kinetic energy of rainfall, while they from hillslopes having sparse coverage were dominated by effective potential energy of surface runoff. The dissipated energy due to interrill erosion showed the highest correlation coefficient with the effective energy under various cover conditions. The kinetic energy of raindrops was greatly reduced by the litter layer and the potential energy of rainwater decreased predominantly due to infiltration. The ratio of effective potential energy of surface runoff to total effective energy was the highest at 71.2% in the plots with low vegetation coverage. The energy efficiency for interrill erosion increased with decreasing vegetation coverage and reached maximum 1.35% in extreme rainfall event under low vegetation coverage. The constant and exponent of power-law functions between the effective energy and the soil erosion work were strongly correlated with gravel ratio and litter coverage, respectively. The results indicate that the effective energy is useful erosivity factor to evaluate the interrill erosion occurred by the complicated interaction of rain splash and sheet flow on vegetated hillslopes.

Effects of granular shape on shear modulus and damping ratio of gravel

The effects of the consolidation ratio, effective confining pressure, gravel content, and granule breakage on the shear modulus and damping ratio of gravel have been extensively researched in recent years. However, studies on the effect of the granular shape are rare. Thus, under different confining pressures, dynamic triaxial tests were performed on gravel specimens to investigate the effect of granular shape on the shear modulus and damping ratio of gravel specimens by using a multifunctional triaxial testing instrument. The samples consisted of two kinds of gravel with the same grain composition and relative density of 45%. The test results indicate that, when the confining pressure and shear strain amplitude exceed 300 kPa and 7×10-4, respectively, gravel with a round granular shape has a higher shear modulus compared to an angular shape. Conversely, when the shear strain amplitude exceeds 2×10-4, the damping ratio of angular gravel exceeds that of round granules.

Variation in plant functional groups indicates land degradation on the Tibetan Plateau

Plant functional groups (PFGs) have been increasingly introduced in land degradation (LD) studies; however, it is unclear whether PFGs can indicate LD. Here, we selected five different degraded lands (i.e., pristine and, lightly, moderately, seriously and extremely degraded) higher than 4650 m on the Tibetan Plateau. In addition, we investigated floristic metrics (i.e., composition, height, cover, biomass and abundance) and soil conditions (e.g., moisture, temperature and gravel ratio) by sampling 225 subplots. We found 75 vascular plants that consist of sedges (Cyperaceae), grasses (Gramineae), legumes, forbs, cushion plants and shrubs PFGs. LD dramatically deteriorated soil conditions, vegetation cover and productivity, however, improved species diversity. Moreover, cover and productivity showed a hump-shaped relationship with LD intensification in legumes, grasses and forbs and decreased mainly in sedges. Productivity increased considerably in cushion plants and shrubs on the extremely degraded land. Major characteristics of the LD process were the replacement of Kobresia spp. by Carex spp. in sedges; cushion plants significantly expanded, and shrubs appeared on the extremely degraded land. We, thus, confirm that the PFG variations are likely to indicate a LD process and demonstrate ways of using PFGs to assess LD status on the Tibetan Plateau.

Bathymetry and siltation rate for Dokan Reservoir, Iraq

AbstractThe Dokan Reservoir dam is a concrete cylindrical arch with gravity abutments, located on the Lesser Zab River about 60 km from the city of Sulaimani in north‐eastern Iraq. A bathymetric survey was conducted in November 2014 for a period of 10 days, using an echo sounder of 200‐kHz single beam. The survey results indicated an annual average sediment deposition of 3.8 million m3. Thirty‐two sediment samples were collected from the reservoir bed. The ratio of gravel, sand, silt and clay was 15:14:48:23, respectively. The reservoir bed is covered mainly with silt. The sediments are composed of silty clay (77.6%), silty sandy clay (10%), sandy gravely silty clay (1.2%) and gravely sandy silty clay (1%).

회귀분석을 이용한 경주·울산 지역에 분포하는 단층 핵의 전단강도 범위 설정

A fault is one of the critical factors that may lead to a possible ground collapse occurring in construction site. A fault core, however, possibly acting as a failure plane in whole fault zone, is composed of fractured rock and gouge nonuniformly distributed and thus can be characterized by its wide range of shear strength which is generally acquired by experimental method for stability analysis. In this study, we performed direct shear test and grain size distribution analysis for 62 fault core samples cropped from 12 different spots located in the vicinity of Kyongju and Ulsan, Korea. As a result, the range of shear strength representing the characteristics of fault cores in the study regions is determined with regard to vertical stress using a regression analysis for experiment data. The weight ratio of gravels in the samples is proportional to the shear strength and that of silt and clay is in inverse proportion to the shear strength. For most samples, the coefficient of determination is over 0.7 despite of inhomogeneity of them and consequently we determined the lower limit and upper limit of the shear strength with regard to the weight ratio by setting the confidence interval of 95%.

砂礫州における礫率の空間分布が伏流水動態に与える影響

Subsurface water flow in a gravel bar is closely related to the river environment and stream ecological system. In this study, we investigated the characteristics of subsurface water flow focusing on a gravel bar which has various heterogeneous effects, such as permeability and porosity of gravels, and bar shapes, during normal flow stage. A network of wells was established to measure water table elevations in gravel bars of gravel bed rivers in Tokyo, Japan. Permeability and porosity of subsurface layer were surveyed by considering the relationship with "gravel ratio" as a new indicator. The characteristic results suggested are: 1) the subsurface water almost stop flowing in downstream part of gravel bar based on the consideration of the relationship between the gravel ratio and permeability, and 2) the binary particle groups is effective to present permeability and porosity of gravel bed in actual river. These above mechanisms are verified using by experiments and the numerical simulation model. Thus, this suggested that the water exchange characteristics through both of surface and subsurface layer in the gravel bar are restrictive.

静岡・清水海岸でトレンチ掘削調査により得られた砂と礫の堆積構造

Trenches were excavated to observe the sedimentary strata on three beaches in Shizuoka, Japan. The western trench was near the Abe River, which is the source of sediment transport; the eastern trench was on the Miho Spit that marks the end of the longshore sediment transport, and the third was in between the two. The strata of the walls of the trenches were recorded and the grain-size distribution of each stratum analyzed. It was found that the grain-size accumulation curve could be divided into five groups based on the ratio of gravel to sand. This shows that conditions of sediment transport affect sediment content. Trench wall strata provide evidence of the strata-forming events.

Study of Mechanical Behavior of Chips Reinforced Concrete

Mechanical behavior of steel fiber reinforced concrete has been studied by the direct tensile test. This fiber concrete is obtained by adding machining chips to the bare concrete. Six fiber contents were adopted (W=0.4%, 0.6%, 0.8%, 1%, 1.2% and 1.5%) for two sand over gravel ratio (S/G = 0.8 and S/G = 1). The results obtained showed that the fibers have substantially improved the stiffness and the strength of concrete and conferred a significant ductility to the material for the fiber volume fractions 0.4%, 0.6% and 0.8% (according to the S/G). The value of residual strength observed after cracking of the concrete matrix was of the same order as for the bare concrete for some of the compositions. Besides the tensile tests, compression tests have been performed. These tests showed that adding a low fiber percentage (W = 0.4%) provides a slight increase of the resistance to compression. Values of W greater than 0.8% lower this resistance. We can conclude that the presence of fibers in concrete is positive, bridging of micro cracks and recovery of the efforts through the developed macro cracks. Unfortunately, the reduction of the compactness has led to a decrease in the tensile strength and the compressive strength. The most advantageous fiber contents for compression are W = 0.4% and W = 0.6% for the two ratios .As for the tensile test, the most advantageous fiber contents are 0.6% and 0.8%.

Artificial neural network model for steel–concrete bond prediction

In this paper, an Artificial Neural Network (ANN) is proposed for modelling the bond between conventional ribbed steel bars and concrete. The purpose is to predict the ultimate pull-out load from the concrete mix constituents (first ANN model) or the compressive strength (second ANN model) and from the steel bar diameter according to the RILEM test configuration [RILEM. Essai portant sur l’adhérence des armatures du béton: essai par traction. Materials and Structures 1970; 3 (3) 175–78]. The ANN models were implemented using an experimental database of 112 pull-out test results performed with ribbed bars 10 mm or 12 mm in diameter and three concrete mixes with different constituent proportions. A Multi-Layer-Perceptron was trained according to a back-propagation algorithm. The first model has six inputs (ANN-6): the diameter of the ribbed bar, the water to cement ratio, the gravel to sand ratio, the crushed to rolled gravel ratio, the type of cement and the concrete maturity. The second model has two inputs (ANN-2): the diameter of the bar and the concrete compressive strength. The ultimate pull-out load was the output data for both models. The results show that the implemented models have good prediction and generalisation capacity with low errors. The ANN-6 model is more accurate, regarding the generalisation capacity, than the ANN-2 model. Concrete mix constituents as input parameter, instead of the compressive strength, are more representative of the local phenomenon at the steel-ribs-to-concrete interface.