公路桥梁中集料试验检测技术研究

集料试验检测在公路桥梁工程原材料选取、设计和使用等过程中具有的重要意义。鉴于此,分别对粗、细集料的试验检测项目的步骤、计算方法和注意事项进行了深入分析,旨在为保证集料质量提供参考。

Landslides & Debris Flows Formation from Gravelly Soil Surface Erosion and Particle Losses in Jiangjia Ravine

Gravelly soils are made up of gravel, sand, silt and clay. They are widely used in engineering applications such as rock-fill dams with clay cores, which are the main researches at present. The strength and mechanical properties of the gravelly soils are affected by the content of coarse grain, fine particles, and their adhesive states. These Properties can be verified by laboratory unconsolidated undrained triaxial tests with grain size less than 5 mm and by large scale direct-shear tests with original grain content. Fine particles of the loose gravelly slopes are released under rainfalls, alternated the structures and mechanical properties, even affected the slope stability. There are a series of large scale direct-shear tests with different coarse grain contents to study the influence of fine particles releasing and migration, results showed the strength behavior of the gravelly soils were affected by the coarse grain content （5） and the inflection coarse grain contents. In order to study the erosion features of the gravelly soil slopes on rainfall conditions and the slopes stability alteration, we had carried out one sort of artificial rainfall local and model experiments, the runoff sediment contents were monitored during the experiments. Result showed that the shapes of the slopes surface transformed periodically, runoff sediment contents were divided into five phases according to the experiment phenomena, runoff sediment contents maintained downtrend during the rain time and the downtrend was obviouslyinterpreted by one descend belt no matter the rainfall intensity and the slope angels. Particle size analysis released the deposit on the slope surface lost almost all of the clay, most of the silt and sand after the experiments, this meant the fine particles releasing, migration and accumulation process on condition of rainfall resulted in the instability factor of the slopes even induced landslide or debris flow.

Characteristics of vibration liquefaction of saturated medium sandy soil with silt

In order to understand and master the dynamic characteristics of sandy soil with different silt contents, the authors carried out many indoor dynamic triaxial tests for five groups of sandy with silt which took from Panjin and Xiamen. Under the conditions of consolidation pressure of 100 kPa, 200 kPa, 300 kPa, stationary vibration frequency H=1 and cyclic loading, the authors found that the effective cohesion increases and the effective internal friction angle decreases with the increase of the silt contents. During the liquefied scope, the cementation and the strength have been increased with the increase of the silt contents.

Effect of Micro Silica on Compressive Strength of Plastic Concrete

This research describes a series of laboratory tests performed to characterize the mechanical properties of plastic concrete. The mechanical properties of plastic concrete are studied using a series of compression tests. Stress relaxation and controlled rate of loading tests are also performed to investigate the rate sensitivity and time-dependency of plastic concrete. An important requirement for the plastic concrete in such applications is adequate strength for the design loads. The replacement of cement content of plastic concrete by micro silica does not result in any significant decrease in workability of plastic concretes and hence, unlike the case for normal concretes, plasticizers or super plasticizers are not required to rectify the adverse effect of micro silica on workability. The aim of the experimental research was to investigate the effects of various levels of cement replacement by micro silica, including 0%, 3%, 6%, 9%, 12% and 15% on strength of plastic concrete. Obtained results show that the effect of micro silica on strength enhancement of plastic concretes is substantial and a replacement level of 15% resulted in 70%-180% increase in strength compared to the control mix. For normal concretes, the increase in strength due to incorporation of micro silica was generally reported as 30%-50%.

关于JGJ 52—2006《普通混凝土用砂、石质量及检验方法标准》执行中若干问题的思考

JGJ 52—2006《普通混凝土用砂、石质量及检验方法标准》实施以来为普通混凝土用砂、石的选择及质量控制提供了重要的标准依据。但随着科技的发展、实践的检验等,《普通混凝土用砂、石质量及检验方法标准》执行过程中也暴露出一些问题,如石子针片状颗粒试验方法、石子含泥量试验方法、砂中石粉含量试验方法以及标准用语等。笔者经过长期试验研究,对所提出的问题进行综合分析,并提出意见、建议,以促进标准的完善。

砂子快速检测试验方法

在商品混凝土中生产过程中,砂子的细度、含泥对混凝土工作性能影响和外加剂需求量影响很大,但是如果按照标准方法做周期长、人为因素影响大,造成试验误差大。为了简化试验方法、消除人为造成的误差,我们的快速检测方法是:先取六、七百克湿砂子,做完含水率检测后拿炒干的砂子(不管剩多少量)直接做筛分。做完筛分的料直接去做含泥量检测。