Abstract
Pore gas pressure in soil is an important parameter in many geoscience applications such as evaluating the effects of trapped pore gas pressure on water infiltration through soil mass, optimizing the design of gas extraction wells in landfills and assessing the performance of landfill covers in reducing landfill gas emission. In addition, it has been observed that pore gas pressure affects slope stability in unsaturated soils. However, the pore gas pressure build-up induced by water infiltration is generally ignored in most slope stability analysis by assuming gas pressure to be zero. Therefore, pore gas pressure measurement in soils is crucial to better understand the unsaturated soil behaviour. However, most of current measuring techniques of pore gas pressure are affected by water interruption during the measurement in unsaturated soils, especially at high water content. In this study, a novel gas pressure transducer was developed to measure the pore gas pressure in unsaturated soil within a wide range of water content. The newly developed pore gas pressure transducer mainly consists of an electrical pressure sensor package and an integrated membrane filter which can prevent water leaching through the membrane but allow gas to pass it freely. The performance of the gas pressure transducer was evaluated by a series of permeation tests. The results show that the developed gas pressure transducer has a good repeatability to monitor gas pressure and has a relatively fast response to the gas pressure change in compacted soils. This transducer is able to measure pore gas pressure range of 0~50 kPa of soils within a relatively high range of soil water content.
Highlights
Pore gas pressure in soil is an important parameter in many geoscience applications such as evaluating the effects of pore trapped gas pressure on water infiltration through soil mass [1,2], optimizing the design of gas extraction wells in landfills, assessing the performance of a landfill cover in reducing landfill gas emission [3] and providing high quality data to verify numerical models
It has been observed that pore gas pressure affects slope stability analysis in unsaturated soils [4]
The excess pore gas pressure induced by water infiltration is generally ignored in most slope stability analysis by assuming gas pressure to be maintained at zero
Summary
Pore gas pressure in soil is an important parameter in many geoscience applications such as evaluating the effects of pore trapped gas pressure on water infiltration through soil mass [1,2], optimizing the design of gas extraction wells in landfills, assessing the performance of a landfill cover in reducing landfill gas emission [3] and providing high quality data to verify numerical models. The excess pore gas pressure induced by water infiltration is generally ignored in most slope stability analysis by assuming gas pressure to be maintained at zero This is mainly due to the assumption that pore gas in soil mass is directly open to the atmosphere. It has been used to measure landfill gas pressure in laboratory column tests [6] This type of technique cannot prevent water in soil from permeating into the measuring tube, especially in a high degree of saturation of soil, resulting in unreliable gas pressure measurement. The size of hypodermic needle is small, it is still permeable to both water and gas since there is no stopper at the end of the needle to separate water and gas This means that water can still flow from the soil to the gas pressure measuring system during the. The performance of the gas pressure transducer was evaluated by a series of permeation tests
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