东北苏打盐碱地输水渠道渗流模拟与试验研究

我国土地资源与水资源短缺,合理开发与利用东北苏打盐碱地、提高水资源利用率对国家粮食安全和社会稳定具有重要意义。基于渠道渗流基本理论,结合吉林省大安市海坨乡苏打盐碱地水稻种植项目区建设实践,建立混凝土渠、玻璃钢渠渗流模型,进行有限元模拟分析及测渗试验。研究结果表明:混凝土渠渗流模型呈现底部渗漏较大并向渠道两侧扩散的规律,玻璃钢渠模型渗漏小,防渗性好;通过动水法测渗试验可知,玻璃钢渠较混凝土渠输水损失利用系数降低73.4%,渗漏强度仅为混凝土渠的四分之一,研究结果可为苏打盐碱地渠道输水提供新方法。

多功能蒸渗测坑一体化结构在泉州市灌溉试验中心站的应用

泉州市灌溉试验中心站因地制宜地建设了一种符合本地灌溉试验站的混凝土基建结构。该试验站创新采用一体化结构,即蒸渗测坑、大型称重式蒸渗仪、轨道式蒸渗测筒三类蒸渗测坑试验设施建设在同一个地下试验室内,以便开展试验和信息传送。该结构解决了丘陵地区不适合分散式结构的问题,并具有防洪能力强、占地面积小、投资费用小等优点,满足了现代信息化建设要求。该结构属于一种全新的测坑结构,可供全国其他灌溉试验站参考。

一种简易蒸渗测坑地下供排水装置的研制

蒸渗测坑现有的地下自动供排水装置水量的计算是采用单次水量固定,用计数器采集电磁阀动作次数,然后计算总水量,该方法忽略了供排水柱(有机玻璃材料)内径沿高度方向的差异,以及水柱内水位波动对水位保持器的影响所带来的误差,同时自动控制的电器元件安装在地下,影响使用寿命,造成前期投入较大、维修费用较高。为了解决这一问题,对现有装置进行了改进,改进装置用高精度流量仪表直接测量进入平水箱的水量,用水力自动控制方法维持蒸渗测坑水位在一定区间波动,该装置可以完成现有装置所有功能。用模拟蒸发实验对两种装置的供水精度进行比较,实验表明,改进装置供水量的测量精度接近或优于现有装置,初步估算前期投入可节省投资20%~30%,且运行维护简单。

Comparative experimental investigation of chemical grouting into a fracture with flowing and static water

We present a series of experimental tests on chemical grouting into a fracture with flowing and static water,using a transparent fracture grouting experimental device.Variations of seepage pressure and grout propagation were compared in our investigation.The results show that flowing water results in drops of seepage pressure,development of penetration radii in the upstream side and drops of propagation area during the same period,compared with grouting in static water.The propagation area in static water is always round before grouts reach the joint boundaries.However,the propagation shape changes from round to an elliptic shape for grouting into a fracture with flowing water.A theoretical model for the grout penetration radius in a fracture considering flowing velocity was developed and validated by our experimental results.These results are helpful in improving understanding of fracture grouting mechanism and in guiding engineering practices.

Influences of rainfall infiltration on stability of accumulation slope by in-situ monitoring test

In order to improve the understanding of the fundamental mechanism of rainfall infiltration induced landslides in accumulation slope and to clarify some important characteristics of slope performance,artificial rainfall simulation tests and field synthetic monitoring were carried out on a typical accumulation slope of Shangrui Freeway in Guizhou Province,China.The monitoring results show that the most accumulation landslides caused by rainfall infiltration are shallow relaxation failure,whose deformation zone lies within the top 0-4 m soil layer.The deformation of slope gradually reduces from the surface,where the greatest deformation lies in,to the deep part of slope.The average percentage of infiltration during the first 2 h is 86%,and then it reduces gradually with time because of the increase of the surface runoff.The average percentage of infiltration drop to a relatively stable value(50%)after 6 h.Rainfall infiltration causes obvious increase of pore-water pressure,which may result in a reduction of shear strength due to a decrease in effective stress and wetting-induced softening.The double-effect of rainfall infiltration is the main reason of rainfall infiltration induced landslides in accumulation slope.

Vacuum preloading combined electroosmotic strengthening of ultra-soft soil

To assess the effectiveness of vacuum preloading combined electroosmotic strengthening of ultra-soft soil and study the mechanism of the process, a comprehensive experimental investigation was performed. A laboratory test cell was designed and applied to evaluate the vacuum preloading combined electroosmosis. Several factors were taken into consideration, including the directions of the electroosmotic current and water induced by vacuum preloading and the replenishment of groundwater from the surrounding area. The results indicate that electroosmosis together with vacuum preloading improve the soil strength greatly, with an increase of approximately 60%, and reduce the water content of the soil on the basis of consolidation of vacuum preloading, howeve~ further settlement is not obvious with only 1.7 mm. The reinforcement effect of vacuum preloading combined electroosmosis is better than that of electroosmosis after vacuum preloading. Elemental analysis using X-ray fluorescence proves that the soil strengthening during electroosmotic period in this work is mainly caused by electroosmosis-induced electrochemical reactions, the concentrations of Al2O3 in the VPCEO region increase by 2.2%, 1.5%, and 0.9% at the anode, the midpoint between the electrodes, and the cathode, respectively.

Effects of discontinuities on penetration of TBM cutters

Based on the triaxial testing machine and discrete element method, the effects of embedded crack on rock fragmentation are investigated in laboratory tests and a series of numerical investigations are conducted on the effects of discontinuities on cutting characteristics and cutting efficiency. In laboratory tests, five propagation patterns of radial cracks are observed. And in the numerical tests, firstly, it is similar to laboratory tests that cracks ahead of cutters mainly initiate from the crushed zone, and some minor cracks will initiate from joints. The cracks initiating from crushed zones will run through the thinner joints while they will be held back by thick joints. Cracks tend to propagate towards the tips of embedded cracks, and minor cracks will initiate from the tips of embedded cracks, which may result in the decrease of specific area, and disturbing layers play as ‘screens', which will prevent cracks from developing greatly. The peak penetration forces, the consumed energy in the penetration process and the uniaxial compression strength will decrease with the increase of discontinuities. The existence of discontinuities will result in the decrease of the cutting efficiency when the spacing between cutters is 70 mm. Some modifications should be made to improve the efficiency when the rocks containing groups of discontinuities are encountered.

Experimental Studies on Penetration of Pulverized Clay-Based Grout

For the geological disposal of high level radioactive wastes, an excavation damaged zone （EDZ） having high hydraulic conductivity resulting from the development of fractures in the rock adjacent to the tunnels will be one of the potential pathways for radioactive contaminant transport. The potential pathways will be sealed by closure components, that is, a combination of tunnel plug, backfill and grout, the latter material being a clay-based mixture in consideration of the need for long-term stability of the seals. Clay-based grout is one of the effective candidate materials that can be used to interrupt the migration of radionuclides through an EDZ. Laboratory testing of clay-based grout using pulverized bentonite, with the objective of improvement in grout penetration into a rockmass, was conducted. The results showed that the pulverization of clay-based grout had a positive effect on filtration.