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Zhang Q.,Chang'an University | Xie Y.,Chang'an University | Liu B.,Chang'an University | Tang J.,Yunnan Broadvision Engineering Consultants
Jiangsu Daxue Xuebao (Ziran Kexue Ban)/Journal of Jiangsu University (Natural Science Edition) | Year: 2017

The normal and the air-entrained concretes with different water-cementmass ratio were designed to investigate the influence of recycled fine aggregate on mechanical properties and freeze-thaw resistance of concrete with different strength grade through varying the replacement rate of recycled fine aggregate. The results show that the compressive strength and the flexural strength of normal concrete markedly decrease with the increasing of replacement ratio of recycled fine aggregate. The compressive strength of air-entrained concrete is obviously decreased with the increasing of replacement ratio of recycled fine aggregate, while the flexural strength is less affected. The resistance to freezing and thawing of concrete with high water-cement ratio (m(water) ∶m(cement)=0.52) is poor with or without recycled fine aggregate. The resistance to freezing and thawing of concrete can be improved with limited extent through adding air-entraining agents. The anti-frost performance of concrete with low water-cement ratio (m(water) ∶m(cement)=0.35) is naturally endowed and is not degraded noticeably by adding recycled fine aggregate. Adding air-entraining agents has little effect for improving the resistance to freezing and thawing. Compared with adding air-entraining agents, the performance of freeze-thaw resistance of recycled fine aggregate concrete can be improved noticeably by decreasing water-cement ratio. © 2017, Editorial Department of Journal of Jiangsu University. All right reserved.

Zhang Q.,Shanxi University | Huang M.,Yunnan Broadvision Engineering Consultants | Chen H.,Shanxi University
Progress in Civil, Architectural and Hydraulic Engineering - Selected Papers of the 4th International Conference on Civil, Architectural and Hydraulic Engineering, ICCAHE 2015 | Year: 2016

Rock samples of different sizes have different uniaxial compressive strengths. In this study, based on actual project, we process samples of different sizes and measure their uniaxial compressive strength. Contrastive analysis shows that uniaxial compressive strength decreases with the increase of sample size. Through fitting, we get the relation formula between uniaxial compressive strength and size effect. When side length of sample is 30 mm, the uniaxial compressive strength is close to the standard strength defined in the code. In actual project, if sample size can not meet the required finish size of the code due to limitation of project conditions, we can process 30 mm samples, measure its uniaxial compressive strength, and then calculate the compressive strength of standard samples using the formula. © 2016 Taylor & Francis Group, London.

Xu Q.,Tongji University | Zhu H.,Tongji University | Ding W.,Tongji University | Li Z.,Yunnan Broadvision Engineering Consultants | Luo Y.,Shenzhen Traffic Utilities Construction Center
Modern Tunnelling Technology | Year: 2014

Instability and even failure of surrounding rock are often caused by excessive rock deformation or local stress concentration when tunneling in soft surrounding rocks, and the anchor bolt is mainly used in practical engineering for initial support. Based on soft surrounding rock of grade IV, tunnel construction with bolt support was simulated by a similarity model test, and the progressive failure feature, failure mode of the surrounding rock, and supporting effects of an anchor bolt were studied. The results show that a stress disturbance area will be formed around the tunnel by excavation, but only a part of the disturbance area really will be damaged. Because of the support of the anchor bolt, rock damage on the crown presents a partitional failure mode, and the failure area of the rock is mainly concentrated in the sector formed by two tunnel sides with an angle of 45° + φ/2 to the horizontal plane. After excavation, a pressure-bearing arch, which is mainly located approximately 1.0-1.25B (B= tunnel span) away from the crown, is formed with increasing tangential stress of the rock mass above the crown. ©, 2014, Editorial Office of "Modern Tunnelling Technology". All right reserved.

Zhou D.W.,Yunnan Broadvision Engineering Consultants | Wang R.J.,Yunnan Broadvision Engineering Consultants
Advanced Materials Research | Year: 2014

Severe rutting, cracks and moisture damage are presented on conventional semi-rigid base asphalt pavements not long after completed in China. This phenomenon indicates that conventional philosophy on pavement design could not meet more and more frequent and heavy vehicle. With high structural capacity for high traffic volume and heavy loads, the Perpetual Asphalt Pavements (PAPs) solve those problems well. Meanwhile they need minimal or no major structural rehabilitation and/or reconstruction exercises in their life, which ensures low user-delay. Three PAPs, including semi-rigid base asphalt pavement, flexible base asphalt pavement, and combined base asphalt pavement, are put forward for the northeast area in China considering its climate, traffic characteristic. Finite element method is utilized to analyze response of PAPs under heavy loads. Two key factors, i.e. tensile horizontal strains at the bottom of asphalt layers and compressive vertical strains are investigated. Also the capacities of the structures on bearing overloading are estimated. Four types of wheel and axle, including single axle and single tire, single axle and dual tires, dual axles and dual tires, and tri axles and dual tires are adopted in finite element models. The shapes of tire-pavement contact area are either circular or rectangular to simulate standard load or overloading respectively. When rectangular shapes are adopted, the contact area sizes and the distribution of pressure are varied. Conventional asphalt concrete and high modulus asphalt concrete are adopted. Simulations are done. The competences of the three pavement structures on fulfilling long lives are evaluated. © (2014) Trans Tech Publications, Switzerland.

Zhang Q.,Chang'an University | Tang J.,Yunnan Broadvision Engineering Consultants | Yang X.,Chang'an University
Advanced Materials Research | Year: 2013

Salt expansion deformation of the saline soil is a common form of the roadbed disease in Saline Soil Area. Salt expansion of saline soil refers to volume expansion by the impact of periodic climate changes in nature. Particle distribution characteristics, compaction characteristics, salt composition and salinity and so on are studied to evaluate the basic engineering properties of saline soil in the location of the project. Seven freeze-thaw cycles test and (no) load single-cooling test are designed to clarify the relation between salt expansion and temperature changes, moisture content, overburden pressure. The results provide design and construction experiences for high-grade highway projects in natural coarse saline soil area. © (2013) Trans Tech Publications, Switzerland.

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