The deterioration mechanism of sea-sand concrete was different in different marine areas. An accelerated test chamber was designed to simulate the marine environment. Semi-immersion and drying - wetting cycle test were carried out on seawater and siliceous sea-sand concrete (SSC), coral aggregate seawater concrete (CASC) and tap water and desalted siliceous sea-sand concrete (DTC). Through the analysis of CT characteristics of sea-sand concrete in different parts and zones, the deterioration performance and safety comparison of sea-sand concrete were studied. The results were as follows: the types of sea salt attack to sea-sand concrete could be divided into internal sea salt attack (ISA), external sea salt attack (ESA) and physical sea salt attack (PSA). ESA, ISA and PSA could increase the cross-sectional area of the specimens and reduce the macropores. ISA, ESA and PSA could promote the expansion effect of each other. However, with the passage of time, the surface of the specimen affected by ESA would be damaged to a certain extent, resulting in the reduction of the cross-sectional area, which could be aggravated by ISA. The effect of ESA and PSA on mortar density first increased and then decreased, and ISA could increase the mortar density. ISA, ESA and PSA could reduce the macropores in concrete. With the same mix proportion (W/C = 0.52) of these three kinds of sea-sand concretes, at the bottom and middle part, DTC was the weakest concrete. In Zone 5 at the bottom part, SSC was also relatively weak. In Zone 1 at the top part, SSC was the safest concrete, while CASC was the weakest. In zone 5 at the top part, DTC was the weakest concrete, and CASC was the safest. (C) 2020 Elsevier Ltd. All rights reserved.

随着近海工程项目的日益增多,海砂可作为经济性建筑材料,但关于高应力作用下海砂的剪切特性研究未见相关文献.通过研究高竖向应力作用下中等粒径海砂的直剪特性,探究了剪切速率对强度指标的影响,得出以下主要结论:(1)随着竖向应力的增大,海砂应力-位移曲线的软化特性越来越突出.(2)海砂达到峰值应力时的位移大致呈现随竖向应力的增大而逐渐增大的趋势.(3)剪切过程中,竖向位移逐渐减小并趋于稳定,表现出剪胀特性.(4)竖向位移-剪切位移关系曲线在初始过程呈现出轻微的剪缩过程,表现为一个较长的稳定阶段,主要是与材料选择与高竖向应力有关.(5)剪切速率对高竖向应力作用下摩尔-库伦曲线的斜率有一定影响,近似可认为随剪切速率的增大,表现为内摩擦的降低.研究成果对近海工程项目建设有一定的参考价值.

The microstructure of hardened cement paste is directly related to its macroscopic properties. Pressurized compact molding can effectively improve the microstructure of hardened cement paste. In order to study the characteristics of pore structure of hardened cement paste and the mechanism of microstructure regulation and defect reduction after pressure compaction, Mercury Intrusion Porosimetry (MIP) and X-Ray Diffraction (XRD) was used to characterize the microstructure of hardened cement paste and the mass fraction of the main phase. Results indicate that the pressurized compact molding significantly reduced the total porosity and critical pore diameter of hardened cement paste, and the pore size was micro-nano. The pore surface fractal dimension (SFD) of the paste was multi-segmental fractal and scale dependent after compaction, and the irregular drift behavior in the transition region was not obvious. A new understanding of the pore volume distribution characteristics of hardened cement paste was proposed based on the change of main phase mass fraction.

As potential building sand, siliceous sea-sand and coral sand had unique physical and chemical properties compared with river sand. In order to study the effect of siliceous sea-sand and coral sand on the mechanics and water transport characteristics of concrete, the mechanical properties (including compression strength and dynamic modulus), water absorption and pore distribution of seawater and siliceous sea-sand concrete (SSC), coralaggregateseawaterconcrete (CASC) and tap water and desalted siliceous sea-sand concrete (DTC) were studied. The influence of volume ratio and pore volume ratio of each solid composition in concrete on the mechanics and water transport characteristics of concrete was investigated.Coral sand had larger porosity and better pore connectivity, so CASC had smaller mechanical properties and density than SSC and DTC, and also had greater water absorption. Since SSC had more salt crystals formed in macropores, the cement paste of SSC were more compact than that of DTC, and SSC had larger mechanical properties and smaller water absorption than DTC. The chemical properties of mixing materials were the main factors influencing the phase and microstructure of cement paste, which could affect the mechanical properties and water absorption of concrete. The material properties of fine aggregate directly affected the mechanical properties of concrete. However, the water absorption of concrete was related to the pore distribution, but not directly related to other properties of fine aggregate. Coarse aggregate was the main carrier for the mechanical properties of concrete, and cement paste also had some influence on them. The main water transport channel of concrete was the pore of cement paste, and the pore of fine aggregate was the auxiliary water transport channel.

In order to study the leaching characteristics of hardened cement paste by flowing environmental water, indoor simulated leaching tests of Portland cement paste were carried out at different flow velocities with home-made flow field device and tap water as the erosion medium. By means of mechanical properties tests, X-ray diffraction (XRD), and Rietveld full-spectrum quantitative analysis of specimens after leaching at different ages, the change rules of the flexural strength, main phase composition, and mass fraction of the specimens after leaching were obtained. The results show that, within 90 days, the flow rate in the test has no obvious effect on the leaching of hardened cement paste. With the increase in age, the leaching of hardened cement paste gets more obvious. Rietveld full-spectrum quantitative analysis shows that the leaching of hardened cement paste changes with the relative content of CaCO3 and Ca(OH)(2). The higher the relative content of CaCO3 is, the better compaction and leaching resistance the paste has. The leaching resistance of hardened cement paste is also related to the gradient of Ca(OH)(2). The smaller the gradient is, the better the leaching resistance is. The Rietveld full-spectrum quantitative analysis method can be used as a method to evaluate the leaching effect of hardened cement paste.

为研究双轴逆向制浆机设备性能和对超细灌浆水泥拌制的适用性,针对浆液的黏度指标和介质分散性,与低速、高速制浆机进行对比试验,并研究了拌制时间对浆体黏度的影响.试验中,浆体设计水灰比分别为0.6、0.8、1.0、2.0和3.0.结果 表明:超细灌浆水泥水灰比大于1时,双轴逆向制浆机可用于超细灌浆水泥的拌制,所制浆液性能与高速制浆机大致相当;拌制超细灌浆水泥,双轴逆向制浆机最佳搅拌时间为3～4min;双轴逆向制浆机所制3种水泥浆液的介质分散性良好.该试验取的经验对灌浆工程设备选择具有指导意义.

随着西北地区城镇化建设的发展,黄土高填方成为一个重要的研究课题.针对黄土高填方项目做了大量室内标准击实试验,对理论问题、影响因素、数值解法进行了研究.研究表明:(1)依据能量守恒原理,通过计算发现我国各行业土工规程中给出的单位体积击实功标准值较延安地区黄土略微偏小;(2)引入含气量概念,发现Q3黄土击实样比Q2黄土击实样含气量高;(3)引入可达到的压实系数概念,通过构造可达到的压实系数与饱和度的关系曲线,发现在特定的干密度条件下,选择最优含水率左侧的含水率数值更为适宜;(4)可以结合几个主要影响构造含水率的最优区间,将含水率控制在最优区间而不是最佳含水率数值,即可以减少水的使用,也能保证施工质量要求.

针对道路桥梁工程专业实践教学存在实践程度高、技术复杂和实习条件艰苦等特点,从专业特点、专业培养目标、岗位能力和企业需求等方面,分析传统顶岗实习的不足,对传统的顶岗实习进行改进和优化,探索并建立相应质量保证体系和应对措施,促进道路桥梁工程专业顶岗实习管理质量的提升.

为了研究水胶比和硅灰掺量对改性超细灌浆水泥浆体流变特性的影响,采用旋转粘度计和马氏漏斗粘度计法对不同水胶比(0.6,0.7,0.8,1.0,1.5和2.0)的新拌水泥浆体进行流变性能试验研究,其中硅灰掺量分别为0％,3％,5％,7％和10％.结果表明,新拌水泥浆体的塑性黏度和屈服应力随着水胶比的增大而减小;掺有硅灰的改性超细灌浆水泥在水胶比大于1.5时,流变性能变化不大,反之则变化较大;硅灰的掺量对改性超细灌浆水泥浆体的流变性影响较大,随着掺量增加浆体流动性变差,但在水胶比为1.0左右时,存在最优掺量,约5％.通过将马氏试验中时间指标转化为流速指标,可以有效拓展高黏度浆体的流变性能测试.

为研究旧料和再生剂掺量对再生混合料的高温性能、低温性能和水稳性的影响,分别采用15％、20％和25％的旧料掺量和5％、7％以及9％的再生剂掺量,制备AC-20再生混合料试件.并对相关试件进行了车辙试验、浸水马歇尔试验和低温弯曲小梁试验.结果表明:(1)试验中再生沥青混合料的高温稳定性、低温性能和水稳定性等技术指标均满足现行规范的要求.(2)随着旧料掺量的增加,再生沥青混合料的动稳定度不断增加,其高温稳定性越好,而再生沥青混合料的残留稳定度呈下降趋势,低温性能变差.(3)掺加6％的再生剂后,再生沥青混合料的残留稳定度提高12％,再生剂有利于提高再生沥青混合料的水稳定性.(4)在旧料掺量为25％,再生剂掺量为6％的情况下,再生混合料的各项性能满足现行规范要求.

为了解超临界CO2技术对土体脱水技术可行性,通过对高岭土和膨润土土样在是否超临界状态下进行的脱水试验分析,研究压力、温度和CO2流量等因素对土体脱水效果的影响.结果表明:试验温度对超临界CO2干燥过程有显著影响,而压力和CO2流量对干燥过程的影响相对较小;高岭土土样在超临界CO2条件下,其自由水脱除效果相比非超临界条件约高1倍;自由水脱除约54.1％,结合水脱除约57.8％,说明超临界CO2条件下土体脱除结合水效果更明显.

文章以滁州市道路工程为例,结合再生沥青混合料发展和工程应用现状,从技术和经济性角度探讨了该工艺的应用前景.由研究结果可知再生沥青混合料技术可较好的在滁州地区推广应用,但需进一步研究该技术拌合设备改造和优化问题;厂拌热再生沥青混合料各项性能均满足规范要求,且厂拌热再生AC-20沥青混合料的成本比AC-20普通沥青混合料降低约4.6％.该技术对滁州市道路工程设计与施工、循环可持续经济发展有一定的参考价值.

The grouting effect will be affected when the cement grout temperature exceeds 40°C. In order to solve the problem, this paper designs a cement grout cooling device and carries out experimental tests of the device’s performance. The cooling experiments are conducted respectively on room-temperature static water (full-water condition and semi-full water condition), flowing hot water and flowing cement grout. The experimental results indicate that the cooling device realizes the function of cooling cement grout and provides reference for design, application and technological optimization of the equipment

The examination of grouting effect has always been a weak link of grouting technology. This paper, based on the high-pressure grouting test of 7# construction tunnel in Tianhuangping Pumped Storage Power, comprehensively evaluates the grouting effect with the combining application of the comparison of drilling water flow, water pressurizing experiment, the comparative method of cement consumption and core-drilling method, to provide reference for grouting construction of similar projects in the future.

通过研究滁州市建筑业发展规划相关文件,梳理出当地建筑业企业发展和人才需求情况.结合当地高职院校建筑类专业办学现状,分析研究现阶段和未来建筑业和高职类建筑教育协调性.结果表明,为实现滁州市建筑业现代化建设目标,滁州市高职院校建筑类人才培养在数量、专业设置、师资队伍建设、实践教学条件等方面存在不足.

This paper analyzes the status of training room construction of civil engineering, discusses the training room construction measures with"teaching, learning and doing"integration, and predicts the training effect of the training room.

通过《公路施工技术》课程项目化教学资源开发，结合滁州职业技术学院及兄弟院校教学改革现状，对比分析了本课程传统模式教学与项目化教学的各自特点。在教学组织与实施后，提炼出项目化教学开发过程中普遍存在的五个方面困境，经分析研究，通过：（1）建立一支优秀的教学团队；（2）加大校企合作力度，强化教学资源建设；（3）加快制度建设，形成长效机制等措施可解决上述困境。实践表明，基于工作过程的施工类课程项目化教学的改革与建设有利于培养出发展型、复合型和创新型的技术技能人才。

In this paper,it analyzes the phenomenon of spalling failure in the process of concrete pile impacted by a hammer. Based on the LS-DYNA nonlinear program,the dynamical performance of concrete pile into the soft soil foundation impacted by a hammer is simulated. Taking into account the theoretical model,some analysis are conducted to discuss the influence factors of the spalling failure. The analysis results show that the compression and tension of stress wave directly influences pile spalling mode. The research results can provide guidance to the design,manufacturing,and construction of piles.

Based on the investigation,analyses and study of ancient bridges in Chuzhou city,some sustainable strategies are put forward to protect and develop these ancient bridges.With help of analyzing their structure,history,present state,and scientific and technical value,this article concludes their architecture culture and scientific and technical values,and promotes four protecting modes and overall developing methods.

There are about 92 ancient bridges in Nanjing City,among which 46 well-known ancient bridges are located in the old town districts approximately,and the other ones are distributed in different counties and districts in Nanjing City.In order to fully understand the structural condition of existing ancient bridges,a survey on ancient bridges is carried out by Nanjing City,which includes the construction time,the historical evolution,the appearance characteristics,the structure form,the service condition,the decay and the maintenance history.Meanwhile,a detailed analysis of the technical parameters and state is carried out on the structures of several well-known old bridges.According to the survey results,it summarizes the current situation and exploits the patterns of ancient bridges,and suggests the relevant protection and the development measures.