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 Experimental Study on Mechanical Behavior of Lean Cemented Sand and Gravel Material in Unloading and Reloading Paths

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Jie Yang ◽  
An-yu Yang ◽  
Yan-gong Shan ◽  
Miao-miao Yang ◽  
Jin-lei Zhao ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Hysteresis Loop ◽  
Triaxial Test ◽  
Volumetric Strain ◽  
Rate Of Change ◽  
Coarse Grained ◽  
Triaxial Tests ◽  
Water Drainage ◽  
Cemented Sand ◽  
Sand And Gravel

Lean cemented sand and gravel (LCSG) materials are subjected to unloading-loading when an LCSG dam is opened for water drainage and then refilled or a roadbed base is subjected to repeated wheel loads. To investigate the behavior of the LCSG materials under loading-unloading, previous studies utilized the complete loading triaxial test. In contrast, in this study, the consolidated drained triaxial tests in the unloading and reloading paths for materials with cementing agent contents of 60 and 100 kg/m3 under different confining pressures, for which each curve generates three loading-unloading cycles, were applied to investigate the unloading and reloading mechanical behavior. Experimental results indicated that the unloading and reloading behavior of the LCSG materials produced stress-strain curves exhibiting a crescent-shaped hysteresis loop, which differs from that exhibited by coarse-grained soil. Although the shape of the crescent-like hysteresis loop was preserved as stress levels increasing, it gradually expanded. Compared with that of the typical triaxial test, the cohesive force and the increasing internal friction angle increased. Further, as the confining pressure increased, the crescent-like hysteresis loops tapered, shear strength increased linearly, and the modulus of resilience increased nonlinearly; the latter’s rate of change, however, decreased. The change in volumetric strain was small during unloading as the stress level changed.

scholarly journals Técnica constructiva de terraplenes húmedos y su aplicación en la geotecnia moderna

2016 ◽  
Vol 17 (3) ◽  
pp. 311
Author(s):  
Gonzalo Carnero ◽  
Erasmo Carnero Carnero
Keyword(s):  
Three Dimensional ◽  
High Capacity ◽  
Sao Paulo ◽  
Triaxial Tests ◽  
Residual Soil ◽  
São Paulo ◽  
Three Dimensional Representation ◽  
Optimum Water Content ◽  
Unsaturated Condition ◽  
Optimum Water

<p align="center"><strong>RESUMEN</strong></p><p>La compactación de suelos en lugares con elevada precipitación pluvial presenta dificultades que afectan los cronogramas físicos y financieros de las obras. Comúnmente, el suelo requiere ser secado cerca a la humedad óptima (+/- 3%), sin embargo, existe la posibilidad de emplear la técnica constructiva de “terraplenes húmedos” que consiste en compactar el suelo con humedades altas, en las cuales, el suelo se encuentra en el “estado quasi-saturado”. Para poder emplear esta técnica, es importante conocer la succión que el suelo tendrá durante la construcción que puede ser obtenida en laboratorio mediante el tensiómetro de alta capacidad (HCT), equipo moderno que monitora la succión en tiempo real. El presente trabajo realiza una revisión de las investigaciones ejecutadas por Marinho y Massad (2011) y Carnero (2014) ambas realizadas con un suelo residual de la Universidade de Sao Paulo, Brasil que fue estudiado ampliamente para conocer su comportamiento en condición no saturada. Los investigadores realizaron ensayos de confinamiento constante (PH), ensayos triaxiales en condición saturada (CU) y no saturada (CW). Los valores de succión de los ensayos PH y CW fueron obtenidos con el HCT y demostraron la eficiencia del equipo. La investigación concluye definiendo el valor de presión de positivación, los parámetros de resistencia efectivos, las ecuaciones de resistencia no saturada según Bishop (1959) y Fredlund et al. (1978) y la representación tridimensional de resistencia en condición no saturada.</p><p> </p> <p> </p><p align="center"><strong>ABSTRACT</strong></p><p>The compaction of soils in places with high rainfall has problems that affects the physical and financial schedule of works. Commonly, the soils requires to be dry in the vicinity of the optimum water content (+/-3 %), however, there is the possibility to use the constructive technique of “wet fills” consisting in compact the soils with high moisture values, in which, the soils is the “quasi-saturated state”. To employ this technique, it is important to know the soil suction during the construction, which it may be obtained in laboratory using the high capacity tensiometer (HCT), modern equipment that monitors the suction in real time. The present work makes a revision of the investigations conducted by Marinho y Massad (2011) and Carnero (2014), both performed with a residual soil from the Universidade de Sao Paulo, Brasil which was broadly studied in order to know its behaviour in unsaturated condition. The researchers conducted constant confined test (PH), saturated (CU) and unsaturated (CW) triaxial tests. The values of suction of the PH and CW tests were obtained by the HCT and validated the equipment efficiency. The research concluded defining the positivation pressure value, the effective strength parameters, the equations of unsaturated resistance according to Bishop (1959) and Fredlund et al. (1978) and the resistance three-dimensional representation in unsaturated condition.</p>

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.

scholarly journals Compressive Behavior of Bamboo Sheet Twining Tube-Confined Concrete Columns

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4124
Author(s):  
Xunyu Cheng ◽  
Yang Wei ◽  
Yuhan Nie ◽  
Gaofei Wang ◽  
Guofen Li
Keyword(s):  
Concrete Strength ◽  
Concrete Columns ◽  
Confined Concrete ◽  
Test Results ◽  
Compressive Behavior ◽  
Concrete Core ◽  
Strain Relationship ◽  
Mode Stress ◽  
New Type ◽  
Good Agreement

This study experimentally investigated various axial compressive parameters of a new type of confined concrete, which is termed bamboo sheet twining tube-confined concrete (BSTCC). This new composite structure was composed of an outer bamboo composite tube (BCT) jacket and a concrete core. Under axial compression, the parameters of thirty-six specimens include concrete strength (i.e., C30 and C50) and BCT thickness (i.e., 6, 12, 18, 24, and 30 layers). The mechanical properties of the BSTCC specimens from the perspective of the failure mode, stress-strain relationship, effect of BCT thickness and dilation behavior were analyzed. The results showed that, in compression, with an increase in BCT thickness in the range of 18-layers of bamboo sheets, the strength increased remarkably. When the strength of the concrete core was high, the confinement effect of the BCT was reduced. In addition, the BCT thickness relieved the dilation of the BSTCC specimens. Finally, the experimental results were compared with predictions obtained from 7 existing FRP-confined concrete models. All the predictions had good agreement with the test results, which further confirmed that the models developed for FRP-confined concrete can provide an acceptable approximation of the ultimate strength of the BSTCC specimens.

scholarly journals Large-Scale Triaxial Tests on Dilatancy Characteristics of Lean Cemented Sand and Gravel

2021 ◽  
Vol 9 ◽  
Author(s):  
Hang Yu ◽  
Xue-mei Shen ◽  
Yu-chen Ye ◽  
Jie Yang ◽  
Chen-hui Zhu
Keyword(s):  
Plastic Strain ◽  
Strain Increment ◽  
Triaxial Tests ◽  
Volume Strain ◽  
Triaxial Loading ◽  
Cemented Sand ◽  
Plastic Strain Increment ◽  
Loading And Unloading ◽  
Sand And Gravel ◽  
Increment Ratio

The dilatancy equation, which describes the plastic strain increment ratio and its dependence on the stress state, is an important component of the elastoplastic constitutive model of geotechnical materials. In order to reveal their differences of the dilatancy value determined by the total volume strain increment ratio and the real value of lean cemented sand and gravel (LCSG) materials, in this study, a series of triaxial compression tests, equiaxial loading and unloading tests, and triaxial loading and unloading tests are conducted under different cement contents and confining pressures. The results reveal that hysteretic loops appear in the stress–strain curves of equiaxial loading and unloading tests, and triaxial loading and unloading tests and that the elastic strain is an important component of the total strain. The hysteretic loop size increases with an increase in the stress level or consolidation stress, whereas the shape remains unchanged. Furthermore, with an increase in the cement content, the dilatancy value determined by the total volume strain increment ratio becomes smaller than that determined by the plastic strain increment ratio, and the influence of the elastic deformation cannot be ignored. Thus, in practical engineering scenarios, especially in the calculation of LCSG dam structures, the dilatancy equation of LCSG materials should be expressed by the plastic strain increment ratio, rather than the total volume strain increment rati.

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 Evaluation of Softening of Clayey Soil Stabilized with Sewage Sludge Ash and Lime

2018 ◽  
Vol 4 (4) ◽  
pp. 743 ◽  
Author(s):  
Kamyar Norouzian ◽  
Nader Abbasi ◽  
Jahangir Abedi Koupai
Keyword(s):  
Sewage Sludge ◽  
Soil Stabilization ◽  
Clayey Soil ◽  
Hydrated Lime ◽  
Sewage Sludge Ash ◽  
Optimum Water Content ◽  
Strength Tests ◽  
New Type ◽  
Sludge Ash ◽  
Optimum Water

Production of sewage sludge have raised increasing concerns due to negative environmental effect. Sewage Sludge Ash (SSA) is used as a new type of additive for clay. Laboratory tests were performed on clay samples to study the mechanism of sewage sludge ash (SSA) and Hydrated Lime (HL) soil stabilization. Different SSA contents (0, 5, 10, 15%) and hydrated lime (0, 1, 3 and 5%) were added to the soil samples. 288 samples were prepared, and unconfined compressive strength tests were carried out. The samples were tested under optimum water content and also saturated conditions with three replications. The results of the coefficient of softening indicated that by adding SSA and hydrated lime to clay soil simultaneously, the stabilized clay soils can be applied in the moist and saturated condition. According to the results, the samples of SSA contents 0% with hydrated lime 5% and SSA contents 10% with hydrated lime 5% can be placed in the vicinity of moisture.

scholarly journals Small-Strain Dynamic Properties of Lean Cemented Sand and Gravel Materials under Different Cementing Agent Contents

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Jie Yang ◽  
Xin Cai ◽  
Yangong Shan ◽  
Miaomiao Yang ◽  
Xingwen Guo ◽  
...  
Keyword(s):  
Dynamic Properties ◽  
Damping Ratio ◽  
Confining Pressure ◽  
Small Strain ◽  
Triaxial Tests ◽  
Dynamic Shear Modulus ◽  
Engineering Applications ◽  
Cemented Sand ◽  
Sand And Gravel ◽  
Cementing Agent

Lean cemented sand and gravel (LCSG) materials are increasingly being used in dams, embankments, and other civil engineering applications. Therefore, their mechanical properties and stress-strain behavior should be systematically understood. In this study, the small-strain dynamic properties of LCSG materials were examined. A series of dynamic triaxial tests were performed to investigate the effects of the confining pressure and cementing agent content of the material on its dynamic shear modulus (Gd) and damping ratio (λ). The results show that Gd increased and λ decreased with increasing confining pressure and cementing agent content; however, under the same confining pressure and cementing agent content, Gd decreased gradually in accordance with shear strain. Furthermore, new expressions were derived for Gd and λ, as well as for their maxima. The results of this study could provide a reference for practical engineering applications, including the construction of dams using LCSG materials.

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.

scholarly journals Molecular Simulation and Theoretical Analysis of Slide-Ring Gels under Biaxial Deformation

Gels ◽  
2021 ◽  
Vol 7 (3) ◽  
pp. 129
Author(s):  
Kotaro Tanahashi ◽  
Tsuyoshi Koga
Keyword(s):  
Theoretical Analysis ◽  
Molecular Mechanism ◽  
Elastic Properties ◽  
Mechanical Characteristics ◽  
Slip Model ◽  
Biaxial Deformation ◽  
New Type ◽  
Cross Links ◽  
Nonlinear Stretching ◽  
Stretching Effect

Slide-ring (SR) gels, a new type of gels that have cross-links moving along the chains, are known to have unique mechanical characteristics. In the case of biaxial deformations, it has been experimentally shown that the stress–strain (S–S) relationships of SR gels can be well described by the neo-Hookean (NH) model. This behavior is quite different from that of conventional chemical gels, where the S–S curves deviate from the NH model. To understand the molecular mechanism of such peculiar elastic properties of SR gels, we studied the effects of movable cross-links by using molecular simulations and theoretical analysis. We calculate the S–S relationships in biaxial deformation for two types of models: slip model, where the cross-links can slide along chains representing SR gels, and non-slip model, which corresponds to conventional chemical gels. In the theoretical analysis, we calculate the S–S relationships by using the models with the Gaussian and the Langevin chains to investigate the nonlinear stretching effect of the chain in the slip and non-slip models. As a result, we found that the peculiar elastic behaviors of SR gels in biaxial deformations are well explained by the effect of movable cross-links suppressing the nonlinear stretching of the chain.

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