تاثير خصوصيات سيال حفره ‌يي حاوي آلاينده‌ي فلز سنگين در خطاي آزمايش هاي تحكيم و حدود اتربرگ

Influence of the Properties of Pore-Fluid Rich in Heavy Metal on Errors Associated with Consolidation and Atterberg Limit Experiments

با توجه به اهميت ويژه ي نتايج حاصل از آزمايش هاي آزمايشگاهي در پروژه هاي ژيوتكنيكي و ژيوتكنيك زيست محيطي، تعيين بازه‌ي قابل اعتمادبودن نتايج آزمايش ها عامل بسيار مهمي در پذيرش نتايج آزمايش ها به‌شمار مي رود. هدف اين پژوهش، تعيين تاثير تغيير خصوصيات الكتروليت سيال حفره‌يي خاك در خطاي نتايج آزمايش هاي تحكيم و حدود اتربرگ است. بر اين اساس، مجموعه ‌يي آزمايش تحكيم و حدود اتربرگ در چند 10 بار تكرار بر روي هر نمونه انجام شده است. در اين راستا، نمونه هاي رسي بنتونيت با غلظت هاي مختلفي از آلاينده‌ي فلز سنگين سرب مورد مطالعه قرار گرفته است. نتايج نشان مي دهد كه تغيير خصوصيات سيال حفره‌يي به‌واسطه‌ي تغيير خصوصيات لايه‌ي دوگانه، مقدار COV نتايج آزمايش هاي حدود اتربرگ را حدود 30 تا 85 درصد و مقدار COV پارامترهاي آزمايش هاي تحكيم را حدود 4 تا 70 درصد تغيير مي دهد.

It is known that engineering judgment and design are significantly a function of experimental results. Due to the importance of the experimental results of geotechnical and geo-environmental engineering projects, determination of the reliability of these experiments is an important factor in the acceptance of experimental investigation. The error associated with these experiments directly influences the reliability of test results. In spite of the importance of determining errors associated with soil mechanics tests, there has been very limited research towards addressing this subject. In addition, most prior research has focused on distilled water as the pore fluid of the soil. Furthermore, no prior research has addressed the influence of heavy metals on the extent of experimental error in soil mechanics experiments. The main objective of this research is to determine the impact of electrolyte properties of soil on the reliability of results of consolidation and Atterberg limit tests. To achieve this objective, a series of consolidation and Atterberg limit experiments, with tens of replicate samples, was performed. In these experiments, bentonite was mixed with different concentrations of heavy metal (lead nitrate). Then, the coefficient of variation of the results was calculated. The results show that the change in the pore fluid properties of soil causes a change in the properties of the soil double layer, which, consequently, affects the error associated with these experiments. For instance, a 30% to 85% change in the COV of the Atterberg limit test and a 4% to 70% change in the COV of the consolidation test were observed once the pore fluid properties of the soil are changed. Finally, it is concluded that the presence of contaminant in different concentrations might increase or decrease experimental error. The results of this research can be used to determine the required replicate samples to achieve specific reliability in consolidation and Atterberg limit tests.