Pavements constructed over loosely compacted subgrades may not possess adequate California bearing ratio (CBR) to meet the requirements of pavement design codes,which may lead to a thicker pavement design for addressi...Pavements constructed over loosely compacted subgrades may not possess adequate California bearing ratio (CBR) to meet the requirements of pavement design codes,which may lead to a thicker pavement design for addressing the required strength.Geosynthetics have been proven to be effective for mitigating the adverse mechanical behaviors of weak soils as integrated constituents of base and sub-base layers in road construction.This study investigated the behaviors of unreinforced and reinforced sand with nonwoven geotextile using repeated CBR loading test (followed by unloading and reloading).The depth and number of geotextile reinforcement layers,as well as the compaction ratio of the soil above and below the reinforcement layer(s) and the compaction ratio of the sand bed,were set as variables in this context.Geotextile layers were placed at upper thickness ratios of 0.3,0.6 and 0.9 and the lower thickness ratio of 0.3.The compaction ratios of the upper layer and the sand bed varied between 85% and 97% to simulate a dense layer on a medium dense sand bed for all unreinforced and reinforced testing scenarios.Repeated CBR loading tests were conducted to the target loads of 100 kgf,150 kgf,200 kgf and 400 kgf,respectively (1 kgf=9.8 N).The results indicated that placing one layer of reinforcement with an upper thickness ratio of 0.3 and compacting the soil above the reinforcement to compaction ratio of 97% significantly reduced the penetration of the CBR piston for all target repeated load levels.However,using two layers of reinforcement sandwiched between two dense soil layers with a compaction ratio of 97% with upper and lower thickness ratios of 0.3 resulted in the lowest penetration.展开更多
Hydroquinone (HQ) is the most important hydroxy aromatic compound which is produced on a large scale. Understanding its fate in the environment is therefore of primary importance to prevent its migration in the soil a...Hydroquinone (HQ) is the most important hydroxy aromatic compound which is produced on a large scale. Understanding its fate in the environment is therefore of primary importance to prevent its migration in the soil and/or the contamination of the aquatic ecosystems. Here we present a column based method to investigate the physicochemical processes controlling the removal from the aqueous phase and the adsorption onto natural quartz sand (NQS), of organic pollutant such as HQ molecules. We will focus on the interactions that occur between the organic pollutant and the NQS substrate. Thus, column reactors filled with NQS were used to investigate the influence of physicochemical parameters such as the ionic strength, the pH, the flow rate, and the nature of the electrolyte cation, on the HQ adsorption from water onto NQS substrate. The data indicate that, when divalent instead of monovalent cations, are present in the effluent water injection phase, and/or when the ionic strength of the effluent increases, the adsorbed HQ amount decreases. Similar decrease of the adsorbed HQ amount was also observed, at constant ionic strength, by increasing either, the pH from 3 to 9, the flow rate Q from 1 to 3 ml·mn-1, or by decreasing the HQ initial concentration, C0 from 30 to 6 mg·L-1. Further, large amount of the organic pollutant (up to 93 wt% of HQ molecules) was removed from the effluent water phase by using NQS column. The overall data seem to indicate that the adsorption of HQ molecules on the NQS surface is mainly controlled by electrostatic interaction forces occurring between the organic molecule polar groups and the inorganic matrix silanol groups.展开更多
建立一种能排除高浓度乳酸菌本底干扰的发酵用乳酸菌菌粉中污染菌总数的检测方法。实验采用不同计数琼脂培养基和不同检验方法测定6种乳酸菌质控样和4种市售发酵用乳酸菌菌粉中乳酸菌的生长情况,确定最优检测用培养基和检验方法,并以4...建立一种能排除高浓度乳酸菌本底干扰的发酵用乳酸菌菌粉中污染菌总数的检测方法。实验采用不同计数琼脂培养基和不同检验方法测定6种乳酸菌质控样和4种市售发酵用乳酸菌菌粉中乳酸菌的生长情况,确定最优检测用培养基和检验方法,并以4种人工污染的乳酸菌菌粉为试样进行方法有效性验证。结果表明:乳酸菌菌粉稀释样经微孔滤膜抽滤法和砂芯漏斗过滤处理后,结合不含糖的无碳源菌落计数琼脂(plate count medium without carbon source,PCCS)培养,可在有效抑制菌粉中乳酸菌生长的同时对污染菌进行特异性计数,检测下限低至10CFU/g。该方法具有良好的检测灵敏度,可用于发酵用乳酸菌菌粉中污染菌的快速、准确计数,有效提高菌粉生产过程及终产品的质量管控。展开更多
文摘Pavements constructed over loosely compacted subgrades may not possess adequate California bearing ratio (CBR) to meet the requirements of pavement design codes,which may lead to a thicker pavement design for addressing the required strength.Geosynthetics have been proven to be effective for mitigating the adverse mechanical behaviors of weak soils as integrated constituents of base and sub-base layers in road construction.This study investigated the behaviors of unreinforced and reinforced sand with nonwoven geotextile using repeated CBR loading test (followed by unloading and reloading).The depth and number of geotextile reinforcement layers,as well as the compaction ratio of the soil above and below the reinforcement layer(s) and the compaction ratio of the sand bed,were set as variables in this context.Geotextile layers were placed at upper thickness ratios of 0.3,0.6 and 0.9 and the lower thickness ratio of 0.3.The compaction ratios of the upper layer and the sand bed varied between 85% and 97% to simulate a dense layer on a medium dense sand bed for all unreinforced and reinforced testing scenarios.Repeated CBR loading tests were conducted to the target loads of 100 kgf,150 kgf,200 kgf and 400 kgf,respectively (1 kgf=9.8 N).The results indicated that placing one layer of reinforcement with an upper thickness ratio of 0.3 and compacting the soil above the reinforcement to compaction ratio of 97% significantly reduced the penetration of the CBR piston for all target repeated load levels.However,using two layers of reinforcement sandwiched between two dense soil layers with a compaction ratio of 97% with upper and lower thickness ratios of 0.3 resulted in the lowest penetration.
文摘Hydroquinone (HQ) is the most important hydroxy aromatic compound which is produced on a large scale. Understanding its fate in the environment is therefore of primary importance to prevent its migration in the soil and/or the contamination of the aquatic ecosystems. Here we present a column based method to investigate the physicochemical processes controlling the removal from the aqueous phase and the adsorption onto natural quartz sand (NQS), of organic pollutant such as HQ molecules. We will focus on the interactions that occur between the organic pollutant and the NQS substrate. Thus, column reactors filled with NQS were used to investigate the influence of physicochemical parameters such as the ionic strength, the pH, the flow rate, and the nature of the electrolyte cation, on the HQ adsorption from water onto NQS substrate. The data indicate that, when divalent instead of monovalent cations, are present in the effluent water injection phase, and/or when the ionic strength of the effluent increases, the adsorbed HQ amount decreases. Similar decrease of the adsorbed HQ amount was also observed, at constant ionic strength, by increasing either, the pH from 3 to 9, the flow rate Q from 1 to 3 ml·mn-1, or by decreasing the HQ initial concentration, C0 from 30 to 6 mg·L-1. Further, large amount of the organic pollutant (up to 93 wt% of HQ molecules) was removed from the effluent water phase by using NQS column. The overall data seem to indicate that the adsorption of HQ molecules on the NQS surface is mainly controlled by electrostatic interaction forces occurring between the organic molecule polar groups and the inorganic matrix silanol groups.
文摘建立一种能排除高浓度乳酸菌本底干扰的发酵用乳酸菌菌粉中污染菌总数的检测方法。实验采用不同计数琼脂培养基和不同检验方法测定6种乳酸菌质控样和4种市售发酵用乳酸菌菌粉中乳酸菌的生长情况,确定最优检测用培养基和检验方法,并以4种人工污染的乳酸菌菌粉为试样进行方法有效性验证。结果表明:乳酸菌菌粉稀释样经微孔滤膜抽滤法和砂芯漏斗过滤处理后,结合不含糖的无碳源菌落计数琼脂(plate count medium without carbon source,PCCS)培养,可在有效抑制菌粉中乳酸菌生长的同时对污染菌进行特异性计数,检测下限低至10CFU/g。该方法具有良好的检测灵敏度,可用于发酵用乳酸菌菌粉中污染菌的快速、准确计数,有效提高菌粉生产过程及终产品的质量管控。
