scholarly journals A New Type of Cemented Sand-Gravel (CSG) Mixtures for Water-Tightening of Hardfill Dams

2021 ◽  
Author(s):  
Sina Karimi ◽  
Hamed Farshbaf Aghajani
Keyword(s):  
Cement Hydration ◽  
Cement Content ◽  
Weight Ratio ◽  
Sem Images ◽  
Cemented Sand ◽  
Native Soil ◽  
New Type ◽  
Sand And Gravel ◽  
Compaction Properties ◽  
Native Soils

Abstract This paper aims to achieve a specific type of cemented sand-gravel mixtures with low permeability to implement in the impervious zone of hardfill dams. To this end, various mixtures are prepared by blending two native soils of sand and gravel with different amounts of kaolinite or bentonite additives in presence of various cement content. The compaction properties, uniaxial compressive strength, permeability and scanning electron microscope (SEM) images of mixtures are measured. According to the results, the cemented mixture containing 10% of kaolinite additive regardless of native soil type exhibits the maximum strength. However, the bentonite disturbs the cement hydration in the mixture, and the strength of mixtures especially with high cement content decreases with increasing the bentonite content. The permeability of mixtures is related to the amount of cement and fine additive in the mixture. The permeability of both cemented sand and gravel mixtures decreases with increasing the bentonite additive. However, the kaolinite additive has a limited influence on the permeability of cemented gravel mixtures. The lowest permeability is achieved in the mixture involving the higher amount of bentonite (with a weight ratio of 30%) in presence of adequate cement.

Experimental Study on Mechanical Characteristics of CSG Materials

2011 ◽  
Vol 243-249 ◽  
pp. 2059-2064
Author(s):  
De Gao Zou ◽  
Dong Qing Li ◽  
Bin Xu ◽  
Xian Jing Kong
Keyword(s):  
Mechanical Characteristics ◽  
Shear Failure ◽  
Triaxial Tests ◽  
Cemented Sand ◽  
Optimum Water Content ◽  
Strain Relationship ◽  
Mode Stress ◽  
New Type ◽  
Sand And Gravel ◽  
Optimum Water

Cemented sand and gravel (CSG) is a new type of dam materials. It not only can reduce the waste of resources and environmental pollution, but has the merits of both gravel and concrete. In this study, Cemented sand and gravel specimens with three cement ratios were compacted at optimum water content and cured for 14 days. Based on the consolidated drained shear triaxial tests, the mechanical properties of different proportion of CSG are studied on shear failure mode, stress-strain relationship, shear strength. Research results showed that, with the increasing of the content of cement, the peak and residual strength of CSG were improved, but the failure strains were decreased. In addition, CSG material behaves distinctly softening.

scholarly journals Unified Failure Strength Criterion for Terrace Slope Reinforcement Materials

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Xuan Fang ◽  
Jie Yang ◽  
Jia-Ming Na ◽  
Zhen-Yuan Gu
Keyword(s):  
Cement Content ◽  
Strength Criterion ◽  
Confining Pressure ◽  
Material Strength ◽  
Failure Strength ◽  
Stability Calculation ◽  
Cemented Sand ◽  
Slope Reinforcement ◽  
Rate Of Increase ◽  
Sand And Gravel

This paper presents a study on the failure strength criterion of terrace slope reinforcement materials, such as lean cemented sand and gravel (LCSG) material, under a triaxial stress state. Cement content and confining pressure were selected as major factors to investigate their influence on the peak stress of terrace slope reinforcement materials based on experimental results and data from the literature. The mechanical properties of the LCSG samples, with cement contents of 60, 80, and 90 kg/m3, and noncemented sand and gravel materials were tested under four confining pressure levels (namely, 300, 600, 1000, and 1500 kPa). The results show that the strength of LCSG material improves as the confining pressure increases. When the confining pressure exceeds 1200 kPa, the rate of increase of the strength for LCSG material and other cemented grained materials declines generally. The material strength displays a linear increase with the growth of the cement content. When the axial load rises up to a certain value, damage will occur at the particle cemented site near the shear plane, and the resistance stress generated by the cementation shows a trend of growth first and then attenuation, and concurrently, the friction between particles increases by degrees. Based on the identified strength characteristics of LCSG material under different cement contents and confining pressures, a new strength criterion that incorporates the frictional strengths and the cementing strengths is proposed for LCSG and other similar materials. The results of this work can provide an important theoretical basis for the stability calculation of terrace slopes and LCSG dams.

scholarly journals Effect of Cement Content on the Deformation Properties of Cemented Sand and Gravel Material

2019 ◽  
Vol 9 (11) ◽  
pp. 2369 ◽  
Author(s):  
Jie Yang ◽  
Xin Cai ◽  
Xing-Wen Guo ◽  
Jin-Lei Zhao
Keyword(s):  
Cement Content ◽  
Axial Strain ◽  
Constitutive Models ◽  
Volumetric Strain ◽  
Prediction Method ◽  
Confining Pressure ◽  
Cemented Sand ◽  
Initial Modulus ◽  
Deformation Properties ◽  
Sand And Gravel

Knowing the deformation properties of cemented sand and gravel (CSG) material can help construct reasonable constitutive models for the material, which can be used to simulate the structural performance of various practical projects including CSG dams. In this study, to investigate the effect of cement content on the deformation properties of CSG material, we employ triaxial compressive tests for cement contents of 20, 40, 60, 80, and 100 kg/m3 with a confining pressure range of 0.3–1.2 MPa, and theoretically analyze the results by the regression analysis prediction method. Here, we show that both cement content and confining pressure influence the deformation properties of CSG material: for an increase in cement content, the failure strain decreases and brittleness of CSG material increases; the initial modulus of the CSG material increased exponentially with increasing cement content or confining pressure; the peak volumetric strain and its corresponding axial strain increase linearly with increasing confining pressures, which decrease with increasing cement content; the initial tangent volumetric ratio can also be determined by the peak volumetric strain and its corresponding axial strain.

scholarly journals Similar Materials and Engineering Application of Cemented Sand and Gravel Dam Model

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Qihui Chai ◽  
Zongkun Li ◽  
Juan Wang ◽  
Zelin Ding ◽  
Meiju Jiao
Keyword(s):  
Model Test ◽  
Engineering Application ◽  
Coarse Sand ◽  
The Body ◽  
Normal Operation ◽  
Cemented Sand ◽  
Similarity Principle ◽  
Similar Materials ◽  
New Type ◽  
Sand And Gravel

This paper takes the cemented sand and gravel dam (CSGD) in Shoukoubao reservoir as the prototype to introduce in detail the similarity principle of model test and describe the selection steps of materials for CSG model. It has developed similar materials for CSGD model by mixing coarse sand, barite powder, gypsum powder, cement, and iron powder so as to provide reference for CSGD model test in the future. The dam model test has studied the stress distribution and displacement deformation of the dam during construction and normal operation, in order to provide experimental support for the study of failure mechanism of the CSGD and facilitate the design and construction of dams of this kind. The stress level of the body and the foundation of the model dam varied from 1/9 to 1/17 of the designed compressive strength of dam material. The results showed that CSGD is a safe new type of dams.

scholarly journals Effect of Zeolite on the Compaction Properties and California Bearing Ratio (CBR) of Cemented Sand

2021 ◽  
Vol 11 (3) ◽  
pp. 229-239
Author(s):  
Ghasem Norouznejad ◽  
Issa Shooshpasha ◽  
Seyed Mohammad Mirhosseini ◽  
Mobin Afzalirad
Keyword(s):  
Cement Content ◽  
Correlation Coefficients ◽  
Dry Weight ◽  
California Bearing Ratio ◽  
Dry Density ◽  
Maximum Dry Density ◽  
Cemented Sand ◽  
The Impact ◽  
Compaction Properties ◽  
Cylindrical Samples

This research investigates the impact of zeolite on the compaction properties and California Bearing Ratio (CBR) of cemented sand. For this purpose, firstly, sand, cement (2, 4, 6, and 8% by the sand dry weight), and zeolite (0%, 30%, 60%, and 90% of cement content, as a replacement material) are mixed. Then, various cylindrical samples with sizes of 101×116 mm and 119×152 mm are prepared for compaction and CBR tests, respectively. After curing for 28 days, the samples are tested according to the standards of compaction and CBR tests. The results depict that the use of zeolite reduces Maximum Dry Density (MDD) while it increases Optimum Moisture Content (OMC) of cemented sand. Furthermore, the inclusion of zeolite up to 30% of cement content contributes to the highest CBR values due to the pozzolanic and chemical reactions. Finally, some correlations with high correlation coefficients are proposed between the CBR and MDD of zeolite-cemented sand.

scholarly journals Statistical Law and Predictive Analysis of Compressive Strength of Cemented Sand and Gravel

2020 ◽  
Vol 27 (1) ◽  
pp. 291-298
Author(s):  
Shoukai Chen ◽  
Yongqiwen Fu ◽  
Lei Guo ◽  
Shifeng Yang ◽  
Yajing Bie
Keyword(s):  
Compressive Strength ◽  
Back Propagation ◽  
Back Propagation Neural Network ◽  
Predictive Analysis ◽  
Distribution Law ◽  
Data Set ◽  
Cemented Sand ◽  
Mix Proportion ◽  
Kolmogorov Smirnov ◽  
Sand And Gravel

AbstractA data set of cemented sand and gravel (CSG) mix proportion and 28-day compressive strength was established, with outliers determined and removed based on the Boxplot. Then, the distribution law of compressive strength of CSG was analyzed using the skewness kurtosis and single-sample Kolmogorov-Smirnov tests. And with the help of Python software, a model based on Back Propagation neural network was built to predict the compressive strength of CSG according to its mix proportion. The results showed that the compressive strength follows the normal distribution law, the expected value and variance were 5.471 MPa and 3.962 MPa respectively, and the average relative error was 7.16%, indicating the predictability of compressive strength of CSG and its correlation with the mix proportion.

Factors affecting at-rest lateral stress in artificially cemented sands

1995 ◽  
Vol 32 (2) ◽  
pp. 195-203 ◽  
Author(s):  
Fanyu Zhu ◽  
Jack I. Clark ◽  
Michael J. Paulin
Keyword(s):  
Cement Content ◽  
Vertical Stress ◽  
Specimen Preparation ◽  
Test Results ◽  
Lateral Stress ◽  
Stress History ◽  
Cemented Sand ◽  
Vertical Loading ◽  
Cemented Sands ◽  
Dry Sand

This paper presents the results of a laboratory study on the at-rest lateral stress and Ko of two artificially cemented sands. A modified oedometer ring was used to measure the lateral stress of cemented and uncemented sands. Test materials were No. 3 Ottawa sand and a marine sand with Portland cement. The specimens were prepared using the method of undercompaction to minimize the influence of specimen preparation on test results. The cement contents were 0, 0.5, 1.0, 2.0, 4.0, and 8.0% by the weight of dry sand. The water content of the specimens was 4% of the weight of dry sand and cement. When the sands were cured under zero confining pressure, the test results indicated the following: the at-rest lateral stress in cemented sands decreases significantly with increasing cement content; the relationship between the vertical and at-rest lateral stress is nonlinear and the value of Ko increases with increasing vertical stress; and the lateral stress decreases with sand density and curing period. When the specimens were cured under vertical stress, the value of Ko during the removal of vertical loading increased with both overconsolidation ratio and cement content. Stress history has a significant influence on the behaviour of at-rest lateral stress in cement sands. Key words : cemented sand, Ko, lateral stress, overconsolidation, stress history.

scholarly journals Mechanical Properties of Chitosan-Starch Composite Filled Hydroxyapatite Micro- and Nanopowders

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
Jafar Ai ◽  
Mostafa Rezaei-Tavirani ◽  
Esmaeil Biazar ◽  
Saeed Heidari K ◽  
Rahim Jahandideh
Keyword(s):  
Sol Gel ◽  
Weight Ratio ◽  
Tensile Modulus ◽  
Mechanical Analysis ◽  
Sem Images ◽  
Chitosan Hydrogel ◽  
Size Particle ◽  
Average Size ◽  
Hard Tissue Engineering ◽  
Nano Size

Hydroxyapatite is a biocompatible ceramic and reinforcing material for bone implantations. In this study, Starch-chitosan hydrogel was produced using the oxidation of starch solution and subsequently cross-linked with chitosan via reductive alkylation method (weight ratio (starch/chitosan): 0.38). The hydroxyapatite micropowders and nanopowders synthesized by sol-gel method (10, 20, 30, 40 %W) were composited to hydrogels and were investigated by mechanical analysis. The results of SEM images and Zetasizer experiments for synthesized nanopowders showed an average size of 100 nm. The nanoparticles distributed as uniform in the chitosan-starch film. The tensile modulus increased for composites containing hydroxyapatite nano-(size particle: 100 nanometer) powders than composites containing micro-(size particle: 100 micrometer) powders. The swelling percentage decreased for samples containing hydroxyapatite nanopowder than the micropowders. These nanocomposites could be applied for hard-tissue engineering.

scholarly journals Effects of zinc acetate and cucurbit[6]uril on PP composites: crystallization behavior, foaming performance and mechanical properties

e-Polymers ◽  
2018 ◽  
Vol 18 (6) ◽  
pp. 491-499 ◽  
Author(s):  
Yuhui Zhou ◽  
Li He ◽  
Wei Gong
Keyword(s):  
Impact Strength ◽  
Flexural Strength ◽  
Zinc Acetate ◽  
Crystallization Behavior ◽  
Cell Structure ◽  
Weight Ratio ◽  
Crystallization Rate ◽  
Sem Images ◽  
Improvement Effect ◽  
Lower Temperature

AbstractIn this study, polypropylene (PP) foams were prepared with 1.0 wt% of cucurbit[6]uril (Q[6]), zinc acetate (Zn(Ac)2), Zn@Q[6] (a supramolecular compound synthesized from Q[6] and Zn(Ac)2), or a mixture of Zn(Ac)2 and Q[6] (weight ratio of 1:1) through injection molding in the presence of a chemical blowing agent, azodicarbonamide. The effect of the additions on the crystallization behavior and foaming performance of PP and the mechanical characterizations of the foaming samples were determined. The results showed that the additions can change the crystallization type from homogeneous to heterogeneous, increase the crystallization rate and shrink the size but increase the density of spherulites. Among the additions, Q[6] most significantly altered the crystallization properties. Scanning electron microscopy (SEM) images revealed that the PP foaming performance can be improved by Zn(Ac)2 addition at a lower temperature (175°C); however, further increasing the temperature had an undesirable effect. Q[6] exhibited the optimum foaming improvement effect on PP in a wide temperature range (175–195°C). Adding nanoparticles also enhanced the tensile properties, flexural strength and impact strength of foaming PP at low temperatures. However, with increasing temperature, the poor cell structure demonstrated undesirable effects in terms of tensile strength, flexural strength and impact strength.

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