不同流速及酸化作用下砂岩的力学损伤研究

为研究流动酸性溶液对岩石基本力学参数产生的损伤效应,通过开展砂岩在流动酸性溶液环境下的三轴压缩试验,得到溶液流速对其力学参数的影响规律。基于现场地下水pH值配置相似酸性溶液,将砂岩试件置于pH=7,5,3,流速为0,200,400 mm·s^(-1)的酸性溶液中浸泡49 d,以此来研究酸化侵蚀作用以及溶液流速对砂岩的力学损伤规律。结果表明,浸泡时间越长,溶液p H值呈先增后减趋势,说明了浸泡初期岩样与溶液反应较为强烈,后逐渐趋于稳定,但并没有停止。溶液pH值越低,流速越大,导致岩样质量损失越明显。三轴压缩下流速相同时,岩样的三轴抗压强度随围压增大而上升;围压条件相同时,岩样的三轴抗压强度、内摩擦角与黏聚力均随流速加快而下滑。

Effect of flexural loading on degradation progress of recycled aggregate concrete subjected to sulfate attack and wetting-drying cycles

The degradation progress of recycled aggregate concrete(RAC) subjected to sulfate attack under wetting-drying cycles and flexural loading is studied. Three different stress ratios(0, 0.3 and 0.5) were applied in this test. The variations of relative dynamic elastic modulus Erd and water-soluble SO2-4 contents in RAC were used to evaluate degradation progress. The changes in mineral products and microstructures of interior concrete were investigated by means of X-ray diffraction(XRD), the environmental scanning electron microscope(ESEM) and X-ray computed tomography(X-CT). The results indicate that flexural loading accelerates the degradation of RAC under sulfate attack and wetting-drying cycles by expediting the transmission of SO2-4 into interior concrete. Furthermore, the accelerated effect of flexural loading is more obvious with the increase of stress ratio, that is because higher stress ratios can accelerate the extension of microcracks and generate more channels for the transmission of SO2-4. Also, more expansive products(gypsum and ettringite) are generated by the reaction of Ca(OH)2 with SO2-4, which can further accelerate the degradation of RAC.

Effect of sulfate erosion on strength and leaching characteristic of stabilized heavy metal contaminated red clay

Solidification/stabilization(S/S)technology has been widely used for remediation of the heavy metal contaminated soils.The heavy metal ions will be leached from the stabilized contaminated soil under sulfate erosion conditions,which gives rise tosecondary contamination to the areas around the mine sites.The commonly used Portland cement,fly ash and quicklime were takenas binder raw materials with various mix proportions.And then,the sulphuric acid and nitric acid method was used to investigate theleaching characteristic of stabilized heavy metal contaminated soils.The effects of binder types and binder contents,sulfateconcentrations(1.5,3.0and6.0g/L)and erosion time(0,7,14and28d)on leached concentrations of heavy metal ions fromcontaminated soils were studied.Moreover,a parameter named immobilization percentage(IP)was introduced to evaluate theinfluence of erosion time and sulfate concentration on immobilization effectiveness for heavy metal ions.The results showed that,theleached heavy metal concentrations increased with sulfate concentration and erosion time.Comparatively speaking,the compositebinders that had calcium oxide in it exhibited the worst solidification effectiveness and the lowest immobilization percentage,withthe largest leached heavy metal concentration.

Prolapse gastropathy syndrome may be a predictor of pathologic acid reflux

AIM： To assess the occurrence of gastric acid reflux into the esophagus in endoscopically confirmed prolapse gastropathy syndrome （PGS）. METHODS： Using ambulatory esophageal pH measurement （BRAVOTM wireless esophageal pH monitoring system）, twenty-six patients with PGS were compared with twenty-one patients with erosive esophagitis （EE） as controls. We assessed several reflux parameters, including the percentage of total time at pH 〈 4, and the DeMeester score. RESULTS： There were no statistical differences between the PGS group and the EE group as to mean age, sex ratio and pH recording time. The EE group showed more severe reflux than the PGS group, as evaluated in terms of the longest duration of reflux, the number of reflux episodes, the number of reflux episodes lasting 〉 5 min, the total time with pH 〈 4 during acid reflux episodes, and the DeMeester score, but none of these parameters showed statistically significant difference. Although 53.8% （14/26） of the PGS group and 76.2% （16/22） of the EE group demonstrated pathologic acid reflux （DeMeester score 〉 14.72）, there was no statistically significant difference between the two groups in the incidence of pathologic acid reflux （P = 0.11）. CONCLUSION： There was no statistically significant difference in pathologic acid reflux between the PGS and EE group. These data suggest that endoscopically diagnosed PGS might be a predictor of pathologic acid reflux.