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Research review of the cement sand and gravel (CSG) dam

Xin CAI, Yingli WU, Xingwen GUO, Yu MING

《结构与土木工程前沿(英文)》 2012年 第6卷 第1期   页码 19-24 doi: 10.1007/s11709-012-0145-y

摘要: The cement sand and gravel (CSG) dam is a new style of dam that owes the advantages both of the concrete faced rock-fill dam (CRFD) and roller compacted concrete (RCC) gravity dam, because of which it has attracted much attention of experts home and abroad. At present, some researches on physic-mechanical property of CSG material and work behavior of CSG dam have been done. This paper introduces the development and characteristics of CSG dam systematically, and summarizes the progress of the study on basic tests, constitutive relation of CSG material and numerical analysis of CSG dam, in addition, indicates research and application aspect of the dam.

关键词: cement sand and gravel (CSG) dam     cement sand and gravel (CSG) material     research review    

胶结颗粒料坝——环境友好的新坝型

贾金生, Michel Lino, 金峰, 郑璀莹

《工程(英文)》 2016年 第2卷 第4期   页码 490-497 doi: 10.1016/J.ENG.2016.04.003

摘要:

笔者于2009年提出了胶结颗粒料坝的概念,目的在于修建更安全、更经济的环境友好的大坝。该坝型包括胶结砂砾石坝(曾用名胶凝砂砾石坝)、堆石混凝土坝(或胶结堆石坝)和胶结土坝。本文基于研究和实践,进一步阐述了胶结颗粒料坝的概念和原则,介绍了胶结砂砾石坝、堆石混凝土坝和胶结土坝的新进展。

关键词: 胶结颗粒料坝     胶结砂砾石坝     堆石混凝土坝     胶结堆石坝     胶结土坝     材料特性    

Utilization of MSWI fly ash as partial cement or sand substitute with focus on cementing efficiency and

Lei Zheng, Xingbao Gao, Wei Wang, Zifu Li, Lingling Zhang, Shikun Cheng

《环境科学与工程前沿(英文)》 2020年 第14卷 第1期 doi: 10.1007/s11783-019-1184-6

摘要: Washed MSWI fly ash was used as partial cement or sand substitute. Sand replacing is beneficial for strength, while cement replacement reduces strength. Cementing efficiency factor and mortar pore structure explain the strength results. Health risk assessment was conducted for MSWI fly ash blended cement mortar. CR and HI contributed by different exposures and heavy metals were analyzed. The strength of cement substituted mortar decreases with the increase in fly ash amount, whereas the strength increases when the fly ash is blended as sand substitute. A mortar with highest strength (compressive strength= 30.2 Mpa; flexural strength= 7.0 Mpa) was obtained when the sand replacement ratio was 0.75%. The k value (cementing efficiency) of fly ash varied between 0.36 and 0.15 for the fly ash fraction in binder between 5% and 25%. The k values of fly ash used for sand replacement were all significantly above that used for cement substitution. The macropores assigned to the gaps between particles decreased when the fly ash was used as sand replacement, providing an explanation for the strength enhancement. The waste-extraction procedure (toxicity-sulphuric acid and nitric acid method (HJ/T 299-2007)) was used to evaluate metal leaching, indicating the reuse possibility of fly ash blended mortar. For the mortar with the mass ratio of fly ash to binder of 0.5%, the carcinogenic risks (CR) and non-carcinogenic hazard quotient (HQ) in sensitive scenario for blended mortar utilization were 9.66 × 10-7 and 0.06, respectively; these results were both lower than the threshold values, showing an acceptable health risk. The CR (9.89 × 10-5) and HQ (3.89) of the non-sensitive scenario for fly ash treatment exceeded the acceptable threshold values, indicating health risks to onsite workers. The main contributor to the carcinogenic and non-carcinogenic risk is Cr and Cd, respectively. The CR and HQ from inhalation was the main route of heavy metal exposure.

关键词: MSWI fly ash     Cementing efficiency     Health risk assessment of heavy metal     Sand replacement     Cement replacement    

In situ-based assessment of soil liquefaction potential–Case study of an earth dam in Tunisia

Ikram GUETTAYA,Mohamed Ridha EL OUNI

《结构与土木工程前沿(英文)》 2014年 第8卷 第4期   页码 456-461 doi: 10.1007/s11709-014-0259-5

摘要: The present paper examines the evaluation of liquefaction potential of an earth dam foundation in Tunisia. The assessment of soil liquefaction was made using deterministic and probabilistic simplified procedures developed from several case histories. The data collected from the field investigation performed before and after the vibrocompaction are analyzed and the results are reported. The obtained results show that after vibrocompaction, a significant improvement of the soil resistance reduces the liquefaction potential of the sandy foundation. Indeed, in the untreated layers, the factor of safety drops below 1 which means that the soil is susceptible for liquefaction. However, in the compacted horizons, the values of exceed the unit which justifies the absence of liquefaction hazard of the foundation.

关键词: liquefaction     cone penetration test (CPT)     standard penetration test (SPT)     vibrcompaction     sand    

Long-Term Performance and Microstructural Characterization of Dam Concrete in the Three Gorges Project

Chen Lyu,Cheng Yu,Chao Lu,Li Pan,Wenwei Li,Jiaping Liu,

《工程(英文)》 doi: 10.1016/j.eng.2023.04.017

摘要: This study investigates the long-term performance of laboratory dam concrete in different curing environments over ten years and the microstructure of 17-year-old laboratory concrete and actual concrete cores drilled from the Three Gorges Dam. The mechanical properties of the laboratory dam concrete, whether cured in natural or standard environments, continued to improve over time. Furthermore, the laboratory dam concrete exhibited good resistance to diffusion and a refined microstructure after 17 years. However, curing and long-term exposure to the local natural environment reduced the frost resistance. Microstructural analyses of the laboratory concrete samples demonstrated that moderate-heat cement and fine fly ash (FA) particles were almost fully hydrated to form compact microstructures consisting of large quantities of homogeneous C-(A)-S-H gels and a few crystals. No obvious interfacial transition zones were observed in the microstructure owing to the long-term pozzolanic reaction. This dense and homogenous microstructure was the crucial reason for the excellent long-term performance of the dam concrete. A high FA volume also played a significant role in the microstructural densification and performance growth of dam concrete at a later age. The concrete drilled from the dam surface exhibited a loose microstructure with higher microporosity, indicating that concrete directly exposed to the actual service environment suffered degradation caused by water and wind attacks. In this study, both macro performance and microstructural analyses revealed that the application of moderate-heat cement and FA resulted in a dense and homogenous microstructure, which ensured the excellent long-term performance of concrete from the Three Gorges Dam after 17 years. Long-term exposure to an actual service environment may lead to microstructural degradation of the concrete surface. Therefore, the retained long-term dam concrete samples need to be further researched to better understand its microstructural evolution and development of its properties.

关键词: Three Gorges Dam     Long-term performance     Microstructural analysis     Moderate-heat cement     Fly ash    

Numerical simulation of compaction parameters for sand-filled embankment using large thickness sand filling

Wentao WANG, Chongzhi TU, Rong LUO

《结构与土木工程前沿(英文)》 2018年 第12卷 第4期   页码 568-576 doi: 10.1007/s11709-017-0444-4

摘要: The study uses the finite element method to simulate a new technique of highway sand embankment filling in Jianghan Plain district, which can raise the thickness of sand-filled layer from 30 cm to 70 cm and can significantly shorten the construction period based on the guarantee of sand embankment construction quality. After simulating the three compacting proposals carried out on the field test, the study uses COMSOL software to research on the compacting effects of sand-filled layers in larger thicknesses by 22 ton vibratory roller alone, and then to investigate the steady compacting effect of 12 ton vibratory roller. The simulation results indicate that the sand-filled layer thickness of 70 cm is suitable for the new sand filling technique, and the sand-filled embankment project with tight construction period is suggested to choose the 12 ton vibration roller for steady compaction.

关键词: sand embankment     compaction in large thickness     numerical simulation     small size vibratory roller     steady compaction    

Key technical innovations in the construction of Baihetan Hydropower Station Project

《工程管理前沿(英文)》 2023年 第10卷 第2期   页码 367-372 doi: 10.1007/s42524-023-0253-5

摘要: Key technical innovations in the construction of Baihetan Hydropower Station Project

关键词: ultra-high arch dam     columnar jointed basalt     low-heat cement concrete     temperature controlled crack prevention     million-kilowatt unit     intelligent construction    

Unified description of sand behavior

Feng ZHANG, Bin YE, Guanlin YE

《结构与土木工程前沿(英文)》 2011年 第5卷 第2期   页码 121-150 doi: 10.1007/s11709-011-0104-z

摘要: In this paper, the mechanical behavior of sand, was systematically described and modeled with a elastoplastic model proposed by Zhang et al. [ ]. Without losing the generality of the sand, a specific sand called as Toyoura sand, a typical clean sand found in Japan, has been discussed in detail. In the model, the results of conventional triaxial tests of the sand under different loading and drainage conditions were simulated with a fixed set of material parameters. The model only employs eight parameters among which five parameters are the same as those used in Cam-clay model. Once the parameters are determined with the conventional drained triaxial compression tests and undrained triaxial cyclic loading tests, then they are fixed to uniquely describe the overall mechanical behaviors of the Toyoura sand, without changing the values of the eight parameters irrespective of what kind of the loadings or the drainage conditions may be. The capability of the model is discussed in a theoretical way.

关键词: constitutive model     sand     stress-induced anisotropy     density     structure    

Investigation of the seismic behavior of grouted sandy gravel foundations using shaking table tests

Tiancheng WANG; Yu LIANG; Xiaoyong ZHANG; Zhihuan RUAN; Guoxiong MEI

《结构与土木工程前沿(英文)》 2022年 第16卷 第9期   页码 1196-1211 doi: 10.1007/s11709-022-0865-6

摘要: Sandy gravel foundations exhibit non-linear dynamic behavior when subjected to strong ground motions, which can have amplification effects on superstructures and can reveal insufficient lateral resistance of foundations. Grouting methods can be used to improve the seismic performance of natural sandy gravel foundations. The strength and stiffness of grouted sandy gravel foundations are different from those of natural foundations, which have unknown earthquake resistance. Few studies have investigated the seismic behavior of sandy gravel foundations before and after grouting. In this study, two shaking table tests were performed to evaluate the effect of grouting reinforcement on seismic performance. The natural frequency, acceleration amplification effect, lateral displacement, and vertical settlement of the non-grouted and grouted sandy gravel foundations were measured and compared. Additionally, the dynamic stress-strain relationships of the two foundations were obtained by a linear inversion method to evaluate the seismic energy dissipation. The test results indicated that the acceleration amplification, lateral displacement amplitude, and vertical settlement of the grouted sandy gravel foundation were lower than that of the non-grouted foundation under low-intensity earthquakes. However, a contrasting result was observed under high-intensity earthquakes. This demonstrated that different grouting reinforcement strategies are required for different sandy gravel foundations. In addition, the dynamic stress-strain relationship of the two foundations exhibited two different energy dissipation mechanisms. The results provide insights relating to the development of foundations for relevant engineering sites and to the dynamic behavior of grouted foundations prior to investigating soil-structure interaction problems.

关键词: sandy gravel foundation     grouting-treated reinforcement     shaking table test     seismic behavior    

Extending blending proportions of ordinary Portland cement and calcium sulfoaluminate cement blends:

《结构与土木工程前沿(英文)》 2021年 第15卷 第5期   页码 1249-1260 doi: 10.1007/s11709-021-0770-4

摘要: This study extended blending proportion range of ordinary Portland cement (OPC) and calcium sulfoaluminate (CSA) cement blends, and investigated effects of proportions on setting time, workability, and strength development of OPC-CSA blend-based mixtures. Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) were conducted to help understand the performance of OPC-CSA blend-based mixtures. The setting time of the OPC-CSA blends was extended, and the workability was improved with increase of OPC content. Although the early-age strength decreased with increase of OPC content, the strength development was still very fast when the OPC content was lower than 60% due to the rapid formation and accumulation of ettringite. At 2 h, the OPC-CSA blend-based mortars with OPC contents of 0%, 20%, 40%, and 60% achieved the unconfined compressive strength (UCS) of 17.5, 13.9, 9.6, and 5.0 MPa, respectively. The OPC content had a negligible influence on long-term strength. At 90 d, the average UCS of the OPC-CSA blend-based mortars was 39.2 ± 1.7 MPa.

关键词: calcium sulfoaluminate cement     cement blends     hydration reaction     setting     workability     compressive strength    

ITZ microstructure, thickness, porosity and its relation with compressive and flexural strength of cementmortar; influence of cement fineness and water/cement ratio

《结构与土木工程前沿(英文)》 2022年 第16卷 第2期   页码 191-201 doi: 10.1007/s11709-021-0792-y

摘要: A new insight into the interfacial transition zone (ITZ) in cement mortar specimens (CMSs) that is influenced by cement fineness is reported. The importance of cement fineness in ITZ characterizations such as morphology and thickness is elucidated by backscattered electron images and by consequences to the compressive (Fc) and flexural strength (Ff), and porosity at various water/cement ratios. The findings indicate that by increasing the cement fineness the calcium silicate hydrate formation in the ITZ is favored and that this can refine the pore structures and create a denser and more homogeneous microstructure. By increasing cement fineness by about 25% of, the ITZ thickness of CMSs was reduced by about 30% and Fc was increased by 7%–52% and Ff by 19%–40%. These findings illustrate that the influence of ITZ features on the mechanical strength of CMSs is mostly related to the cement fineness and ITZ microstructure.

关键词: cement fineness     interfacial transition zone     compressive and flexural strength    

Study of bond strength between various grade of Ordinary Portland Cement (OPC) and Portland PozzolaneCement (PPC) mixes and different diameter of TMT bars by using pullout test

A D POFALE, S P WANJARI

《结构与土木工程前沿(英文)》 2013年 第7卷 第1期   页码 39-45 doi: 10.1007/s11709-013-0193-y

摘要: Since last two decades, the Portland Pozzolane Cement (PPC) is extensively used in structural concrete. But, till to date, a few literature is available on bond strength of concrete using PPC mixes. There are many literatures available on bond strength of concrete mixes using Ordinary Portland Cement (OPC). Hence, a comparative study was conducted on bond strength between OPC and PPC mixes. In the present investigation, total 24 samples consisting of M20, M35 and M50 grades of concrete and 16 and 25 mm diameter of TMT bar were tested for 7 and 28 days. The pullout bond test was conducted on each specimen as per IS: 2770-1967/1997 [1] and the results were observed at 0.25 mm slip at loaded end called as critical bond stress and at maximum bond load called as maximum bond stress. It was observed that the critical bond strength of PPC mixes is 10% higher than OPC mixes. Whereas, marginal improvement was noticed in maximum bond strength of PPC mixes. Hence, based on these findings, it could be concluded that development length for PPC mixes could be reduced by 10% as compared with same grade of OPC mixes.

关键词: bond strength     Portland Pozzolane Cement (PPC) concrete     Ordinary Portland Cement (OPC) concrete     bond between concrete and steel     pullout test     development length    

Effects of microfine aggregate in manufactured sand on bleeding and plastic shrinkage cracking of concrete

Branavan ARULMOLY; Chaminda KONTHESINGHA; Anura NANAYAKKARA

《结构与土木工程前沿(英文)》 2022年 第16卷 第11期   页码 1453-1473 doi: 10.1007/s11709-022-0877-2

摘要: Construction industries have started to utilize manufactured sand (MS) as an effective alternative for river sand in concrete. High-grade parent rocks are crushed to obtain MS, which also produces a considerable amount of microfine aggregate (MFA). The higher percentage of MFA could lead to both positive and negative effects on the performance of cement-based mixes. This research was done to examine the influence of varying MFA levels, specifically 0%, 3%, 6%, 9%, and 12% (by weight) as the partial replacements of MS on bleeding and plastic shrinkage cracking of concrete. In addition to the varying MFA levels, some concrete mixes also included fly ash (FA) and superplasticizer to investigate the effect of free-water content in the mixes. The bleeding test data were taken as on-site measurements, while the cracks from the plastic shrinkage cracking test were evaluated using an image processing technique. The results concluded that the MFA replacements and the effective water-to-cement ratio have a significant effect on the selected concrete properties. With the increasing replacement levels, cumulative bleeding and crack initiation life gradually decreased, while a progressive increase was observed for crack width, crack length, and crack area.

关键词: manufactured sand     fresh concrete     microfines     admixtures     shrinkage     cracking    

Impacts of backwashing on micropollutant removal and associated microbial assembly processes in sand

《环境科学与工程前沿(英文)》 2023年 第17卷 第3期 doi: 10.1007/s11783-023-1634-z

摘要:

● Backwashing in sand filters with 2-h and 4-h EBCTs was simulated.

关键词: Sand filter     Backwashing     Recovery     Micropollutants     Community composition    

Evaluation of the stability of terraced slopes in clayey gravel soil using a novel numerical technique

《结构与土木工程前沿(英文)》 2023年 第17卷 第5期   页码 796-811 doi: 10.1007/s11709-023-0922-9

摘要: Conventional geotechnical software limits the use of the strength reduction method (SRM) based on the Mohr–Coulomb failure criterion to analyze the slope safety factor (SF). The use of this constitutive model is impractical for predicting the behavior of all soil types. In the present study, an innovative numerical technique based on SRM was developed to determine SF using the finite element method and considering the extended Cam–clay constitutive model for clayey gravel soil as opposed to the Mohr–Coulomb model. In this regard, a novel user subroutine code was employed in ABAQUS to reduce the stabilizing forces to determine the failure surfaces and resist and drive shear stresses on a slope. After validating the proposed technique, it was employed to investigate the performance of terraced slopes in the context of a case study. The impacts of geometric parameters and different water table elevations on the SF were examined. The results indicated that an increase in the upper and lower slope heights led to a decrease in SF, and a slight increase in the horizontal offset led to an increase in the SF. Moreover, when the water table elevation was lower than the toe of the terraced slope, the SF increased because of the increase in the uplift force as a resistant component.

关键词: terraced slope     safety factor     finite element method     ABAQUS     extended Cam–clay    

标题 作者 时间 类型 操作

Research review of the cement sand and gravel (CSG) dam

Xin CAI, Yingli WU, Xingwen GUO, Yu MING

期刊论文

胶结颗粒料坝——环境友好的新坝型

贾金生, Michel Lino, 金峰, 郑璀莹

期刊论文

Utilization of MSWI fly ash as partial cement or sand substitute with focus on cementing efficiency and

Lei Zheng, Xingbao Gao, Wei Wang, Zifu Li, Lingling Zhang, Shikun Cheng

期刊论文

In situ-based assessment of soil liquefaction potential–Case study of an earth dam in Tunisia

Ikram GUETTAYA,Mohamed Ridha EL OUNI

期刊论文

Long-Term Performance and Microstructural Characterization of Dam Concrete in the Three Gorges Project

Chen Lyu,Cheng Yu,Chao Lu,Li Pan,Wenwei Li,Jiaping Liu,

期刊论文

Numerical simulation of compaction parameters for sand-filled embankment using large thickness sand filling

Wentao WANG, Chongzhi TU, Rong LUO

期刊论文

Key technical innovations in the construction of Baihetan Hydropower Station Project

期刊论文

Unified description of sand behavior

Feng ZHANG, Bin YE, Guanlin YE

期刊论文

Investigation of the seismic behavior of grouted sandy gravel foundations using shaking table tests

Tiancheng WANG; Yu LIANG; Xiaoyong ZHANG; Zhihuan RUAN; Guoxiong MEI

期刊论文

Extending blending proportions of ordinary Portland cement and calcium sulfoaluminate cement blends:

期刊论文

ITZ microstructure, thickness, porosity and its relation with compressive and flexural strength of cementmortar; influence of cement fineness and water/cement ratio

期刊论文

Study of bond strength between various grade of Ordinary Portland Cement (OPC) and Portland PozzolaneCement (PPC) mixes and different diameter of TMT bars by using pullout test

A D POFALE, S P WANJARI

期刊论文

Effects of microfine aggregate in manufactured sand on bleeding and plastic shrinkage cracking of concrete

Branavan ARULMOLY; Chaminda KONTHESINGHA; Anura NANAYAKKARA

期刊论文

Impacts of backwashing on micropollutant removal and associated microbial assembly processes in sand

期刊论文

Evaluation of the stability of terraced slopes in clayey gravel soil using a novel numerical technique

期刊论文