Monitoring of drying-induced soil moisture loss with PZT-based EMI technique

Author(s):  
Jianchao Wu ◽  
Jie Fang ◽  
Jianjun Wang ◽  
Yabin Liang ◽  
Weijie Li

Air-drying process of soil is a crucial procedure in geological and geotechnical engineering. Drying-induced ground subsidence and damage to overlying buildings is a widespread and urgent problem. Monitoring of drying-induced water evaporation in soil is of great importance. In this paper, soil moisture loss monitoring based on lead zirconate titanate (PZT) transducer using electro-mechanical impedance (EMI) technique was investigated. A physical model test in our laboratory was conducted to study the feasibility and applicability. In the experimental research, three identical PZT transducers that were wrapped with waterproof insulation glue were pre-embedded inside a cohesive soil specimen. In addition, another PZT transducer was embedded in a sandy soil specimen to explore the application effect in soil with different composition. EMI signatures of these four PZT patches during the air-drying process were collected and analyzed. Experimental results indicated that the peak frequency in the conductance signatures presented a rightward shift as the water evaporates. Moreover, the corresponding peak magnitude keep decreasing with the continuous development of soil moisture loss. To better quantify the variations, two statistical metrics including root mean square deviation (RMSD) and mean absolute percentage deviation (MAPD) were employed to study the changing characteristics of the EMI signatures. All these two metrics increase coincidentally in the process. Experimental results demonstrate that cohesive and sandy soil moisture loss monitoring by using the embedded PZT transducer is feasible and reliable. This work also serves as a proof-of-concept study to demonstrate the performance of the EMI technique in monitoring the soil moisture content.

2019 ◽  
Author(s):  
Ankita Sinha ◽  
Atul Bhargav

Food materials shrink when they are air-dried. However, owing largely to the complexity of modelling, most drying models so far have neglected this shrinkage, leading to inaccurate predictions. The empirical nature, inability to yield data on location-specific deformations and computational cost of detailed poro-mechanistic analyses and complex deformation modelling approaches make them unattractive for models that could be used in real-time process control algorithms. In this work, we develop a simplified transport model to predict spatial and temporal shrinkage during low temperature air drying process, and validate the model with experiments. In such drying, volumetric change is dominated by moisture loss; therefore the role of gas induced porosity is neglected. This model predicts shrinkage, temperature and moisture content at each spatial location at time intervals during the drying process. The model agrees well with experiments conducted by us (reported in this paper) as well as with those conducted by others (taken from the literature) on food samples. We expect that this generalized model will find wide applications in the food processing industry.


2021 ◽  
Author(s):  
Ana M. C. Ilie ◽  
Tissa H. Illangasekare ◽  
Kenichi Soga ◽  
William R. Whalley

<p>Understanding the soil-gas migration in unsaturated soil is important in a number of problems that include carbon loading to the atmosphere from the bio-geochemical activity and leakage of gases from subsurface sources from carbon storage unconventional energy development. The soil water dynamics in the vadose zone control the soil-gas pathway development and, hence, the gas flux's spatial and temporal distribution at the soil surface. The spatial distribution of soil-water content depends on soil water characteristics. The dynamics are controlled by the water flux at the land surface and water table fluctuations. Physical properties of soil give a better understanding of the soil gas dynamics and migration from greater soil depths. The fundamental process of soil gas migration under dynamic water content was investigated in the laboratory using an intermediate-scale test system under controlled conditions that is not possible in the field. The experiments focus on observing the methane gas migration in relation to the physical properties of soil and the soil moisture patterns. A 2D soil tank with dimensions of 60 cm × 90 cm × 5.6 cm (height × length × width) was used.  The tank was heterogeneously packed with sandy soil along with a distributed network of soil moisture, temperature, and electrical conductivity sensors. The heterogeneous soil configuration was designed using nine uniform silica sands with the effective sieve numbers #16, #70, #8, #40/50, #110, #30/40, #50, and #20/30 (Accusands, Unimin Corp., Ottawa, MN), and a porosity ranging in values from 0.31 to 0.42. Four methane infrared gas sensors and a Flame Ionization detector (HFR400 Fast FID) were used for the soil gas sampling at different depths within the soil profiles and at the land surface.  A complex transient soil moisture distribution and soil gas migration patterns were observed in the 2D tank. These processes were successfully captured by the sensors. These preliminary experiments helped us to understand the mechanism of soil moisture sensor response and methane gas migration into a heterogeneous sandy soil with a view to developing a large-scale test in a 3D tank (4.87 m × 2.44 m × 0.40 m) and finally transition to field deployment.</p>


2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Zhijun Zhang ◽  
Shiwei Zhang ◽  
Tianyi Su ◽  
Shuangshuang Zhao

Corns, fruits, and vegetables are usually used as porous medium in drying process. But in fact, it must be considered as the cortex effect on mass transfer because the mass transfer of cortex is very difficult than inner medium. Based on the theory of heat and mass transfer, a coupled model for the porous medium vacuum drying process with cortex effect is constructed. The model is implemented and solved using COMSOL software. The water evaporation rate is determined using a nonequilibrium method with the rate constant parameterKrthat has been studied. The effects of different vapor pressures (1000, 5000, and 9000 Pa), initial moisture contents (0.3, 0.4, and 0.5 water saturation), drying temperatures (323, 333, and 343 K), and intrinsic permeability for cortex part (10−13, 10−14, 10−15 m2) on vacuum drying process were studied. The results facilitate a better understanding of the porous medium vacuum drying process that nearer to the reality.


2008 ◽  
Vol 106 (4) ◽  
pp. 405-408 ◽  
Author(s):  
Toshihide Nakamura ◽  
Satomi Mizukami-Murata ◽  
Akira Ando ◽  
Yoshinori Murata ◽  
Hiroshi Takagi ◽  
...  

Forests ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1788
Author(s):  
Hugh Collett ◽  
Florian Bouville ◽  
Finn Giuliani ◽  
Eleanor Schofield

Large archaeological wooden structures are potentially at risk of structural failure through deformation and cracking over time if they are left untreated and their structural health is not maintained. This could be in part due to, for example, the shrinkage of waterlogged wood as it dries, or time-dependent creep processes. These dimensional changes are accompanied by associated stresses. However, there are few studies analysing the movement of large wooden structures in real time as they dry, particularly after their conservation treatment. This paper follows the structural monitoring of the Mary Rose from after the conservation treatment, where it was sprayed with polyethylene glycol, through to the ship’s air-drying process and beyond to assess the effects that drying has had on the displacement of the timbers. A laser-based target system was used to collect displacement data between 2013 and 2020 and the data showed a significant slowing of displacement as the drying reached an equilibrium.


2020 ◽  
Vol 6 (2) ◽  
pp. 81-87
Author(s):  
Zhanna Petrova ◽  
◽  
Kateryna Samoilenko ◽  
Vitaly Vishnevsky

Red beetroot is the main raw material which has a high content of betanine with antioxidant properties. An important emphasis in the processing of antioxidant raw materials by drying is to reduce energy consumption for the dehydration process, the maximum preservation of biologically active substances, and to reduce the cost of the final product. Drying is a complex and energy-intensive process. Therefore, to optimize energy consumption during drying and selection of rational modes of dehydration, it is necessary to apply the calculated analysis of heat and mass transfer on the basis of adequate mathematical models. Calculated and experimental results are compared. In general, the comparison of the results of numerical modeling of convection drying processes of the red beetroot sample with the experimental results showed their rather satisfactory qualitative agreement. The calculation model can be used to approximate the characteristics of the drying process of red beetroot, in particular the time required for drying. The obtained results of calorimetric studies allow stating that with correctly selected compositions, not only the components of native raw materials are stabilized, but also the drying process is intensified with the reduction of energy consumption to process.


1987 ◽  
Vol 67 (1) ◽  
pp. 43-54 ◽  
Author(s):  
C. P. MAULÉ ◽  
D. S. CHANASYK

Two simple techniques for separating soil moisture loss into drainage and evapotranspiration for cropped conditions were compared. The study was conducted during May through September 1983 at Ellerslie, Alberta. One technique, the field capacity method, utilized soil tension at − 4 kPa to demarcate the cessation of drainage; the other technique, the gradient method, utilized changes in soil moisture status relative to fallow conditions, to mark the onset of moisture extraction by roots. Both methods estimated similar amounts of drainage and evapotranspiration for the barley plots. Application and thus proper evaluation of these two methods were limited as more than 83% of the total drainage occurred during a 3-wk period in which only the Penman method for estimating evapotranspiration could be used. Key words: Water balance, drainage, evapotranspiration, field capacity method, gradient method


2013 ◽  
Vol 12 (21) ◽  
pp. 6154-6158
Author(s):  
Xiao Kang-Yi ◽  
Chuan Feng-Li ◽  
Shu Gang-Li ◽  
He Lei Cui ◽  
Wen Fu-Wu

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