Drainage Experiments Research Articles

Time–lapse monitoring of soil water content by full GPR waveform inversion with Grey Wolf Optimizer

Abstract Ground-Penetrating Radar (GPR) has become a powerful geophysical technique for investigating soil water dynamics. In this study, we proposed an inversion scheme based on Grey Wolf Optimizer (GWO) to monitor the change of SWC from the time-lapse of the full waveform of GPR data. The scheme was applied to GPR data acquired during a drainage experiment. Five traces at different times were selected in the experiment. The results show that the proposed scheme is very promising for directly and non-invasively monitoring of SWC change from the time-lapse of the full waveform inversion of GPR data based on field scale GWO algorithm.

Aperture Field Anisotropy Control on Immiscible Displacement Patterns in Rough Fractures

AbstractTwo‐phase flow displacement in rock fractures is crucial for various subsurface mass transfer processes and engineering applications. In fractures, the displacement of a less viscous fluid by a more viscous one (i.e., viscosity ratio M > 1) involves viscous forces help stabilizing the displacement front in presence of capillary pressure fluctuations. Although previous studies have reported displacement patterns in isotropic fractures, the impact of anisotropic fractures on displacement patterns has not been systematically examined. In this study, we conducted flow‐rate‐controlled drainage experiments to examine how anisotropic aperture fields affect displacement patterns. We observed the transition of displacement patterns from capillary fingering (CF) to crossover zone (CZ) to compact displacement pattern (CD) based on variations in transverse pore‐filling event (TPFE) frequency, which characterizes the competition between capillary and viscous forces. Increasing aperture correlation length in the transverse direction leads to increased TPFE frequency at a low flow rate, destabilizing displacement front. While the increasing aperture correlation length in longitudinal direction suppressed TPFE frequency, stabilizing displacement front. Therefore, the critical capillary number (CaCF‐CZ), which indicates the onset of the CF‐CZ transition, decreases as the aperture field varies from transversely to longitudinally correlated. At high flow rates, TPFEs almost disappeared, indicating that anisotropy did not affect CZ‐CD transition (CaCZ‐CD). Furthermore, we modified theoretical models of CaCF‐CZ and CaCZ‐CD by incorporating the aperture anisotropy factor, achieving a good fit with the experimental data. This study demonstrates the critical role of aperture field anisotropy in controlling two‐phase displacement patterns and provides a theoretical framework for predicting multiphase flow behavior in natural fractures.

Study on the Performance Evaluation Method and Application of Drainage Nonwoven Geotextile in the Yellow River Sediment Filling Reclamation Area

Technical challenges associated with drainage and filling efficacy confront the Yellow River sediment filling reclamation, a novel approach to reclaiming coal-mined subsided lands. This study proposes an improved geotextile performance evaluation method to address the shortcomings of current geotextile screening methodologies in the drainage of the Yellow River sediment. This method comprehensively considers essential characteristics under working conditions, such as permeability, soil conservation, and blockage prevention properties, including indicators such as the permeability coefficient and sediment retention rate of geotextiles under pressure. Indoor flume filling and drainage experiments were implemented to verify the efficacy of geotextile drainage. The improved method identified thermal-bonded nonwoven geotextiles of 200 and 250 g·m−2 as having the highest comprehensive evaluation scores. The experimental results showed that these geotextiles significantly improved their drainage efficiency and better met the specific requirements of the Yellow River sediment filling reclamation. Traditional screening methods may be unsuitable for sediment drainage conditions, necessitating sediment interception and rapid drainage due to the streaming water–sediment mixture. Therefore, the newly established performance evaluation method is more appropriate for the specific requirements. It is recommended that a simple vibrating device be installed to maintain 20 vibrations per minute to keep drainage channels clear and provide stable drainage performance in engineering applications.

Sediment Transport Dynamics Modeling of Overland Flow on Gentle Slopes Based on Flume Experiments

ABSTRACTSoil erosion is a global environmental issue, and sediment transport capacity (T c ) is critical for developing soil erosion models. This study conducted flume drainage experiments at six flow discharges (0.15, 0.25, 0.35, 0.45, 0.55, and 0.65 L s−1) and eight slope gradients (1.5, 3.0, 4.5, 6.0, 7.5, 9.0, 10.5, and 12.0°) to investigate how the T c of gentle slopes in the northeastern hilly region of China and water erosion factors are related and to establish a T c model of overland flow. The study demonstrated a power–law relationship between T c, flow discharge, and slope gradient, as evidenced by a high coefficient of determination (R 2; 0.94) and Nash–Sutcliffe efficiency (NSE; 0.92) values. Additionally, there was a positive correlation between T c and average flow velocity, with R 2 and NSE values of 0.86 and 0.84, respectively. Among the hydrodynamic parameters tested, the average flow velocity was determined to be the most effective T c predictor, surpassing stream power (R 2 > 0.7, NSE > 0.7), shear stress (R 2 > 0.6, NSE > 0.6), and unit stream power (R 2 < 0.5, NSE < 0.5). These findings lay the foundation for developing process‐based sediment transport models for gentle slopes in the northeastern hilly regions of China.

Water retention curves of sandy soils obtained from direct measurements, particle size distribution, and infiltration experiments

AbstractAccurate information about soil water retention curves (SWRCs) of sands is essential for evaluating groundwater recharge and vulnerability to contamination in many shallow sandy aquifers which are widespread on post glacial areas in Northern Europe and North America. Pedotransfer functions (PTFs) allow to estimate SWRC from basic physical characteristics of soils, such as textural composition. However, in the case of clean sands which are dominated by a single textural fraction, PTFs should be based on more detailed information given by the particle size distribution. In this study we evaluated three parametric PTFs, which estimate parameters of the van Genuchten SWRC based on empirical correlations to the parameters of soil particle size distribution, and five semi‐physical PTFs, which derive the pore size distribution from particle size distribution. PTFs were compared to SWRCs fitted to the results of drainage experiments on sandy soil samples from six locations in Gdańsk region (northern Poland). Although in all samples the content of silt and clay fractions was low (<3.5%), the differences in actual content of fines strongly influenced the shape of SWRC. In contrast, the amount of gravel fraction (varying from 1% to 35%) did not have significant effect on SWRC. Semi‐physical PTFs were found to be more accurate than parametric PTFs. The best overall performance was shown by the semi‐physical Chang and Cheng PTF. Among the parametric PTFs the best accuracy was obtained with the Schaap and Bouten method. However, all considered functions showed limited accuracy in higher suction range. Additionally, infiltration experiments were performed on four sites. SWRCs were obtained from ring infiltrometer tests using the Beerkan estimation of soil transfer parameters (BEST) method and from the tension infiltrometer (TI) tests using numerical solution of the inverse problem based on the Richards equation. In almost all cases the wetting SWRCs were characterized by higher values of the pressure scaling parameter α compared to SWRCs measured in drainage experiments, which is consistent with the well‐known phenomenon of hysteresis in soils. However, the BEST method resulted in significantly higher α and hydraulic conductivity Ks than TI, probably due to activation of the largest soil pores during ponded infiltration.

Coupled hydro‐mechanical pore‐scale modeling of biopore‐coated clods for upscaling soil shrinkage and hydraulic properties

AbstractEarthworms and plant roots are vital for macropore formation and stabilization. The organo‐mineral coating of biopore surfaces also regulates macropore‐matrix mass exchange during preferential flow. The influence of finer‐textured burrow coatings on macroscopic soil properties during shrinkage could potentially be assessed by upscaling pore‐scale hydraulic and mechanical simulations. The aim was to investigate the influence of micro parameters (particle size, stiffness, and bond strength) on macro parameters (i.e., shrinkage curve and soil hydraulic properties). Drainage experiments and simulations were carried out using biopore‐coated clod‐size samples compared to those without coating. Simulations were performed using a two‐phase pore‐scale finite volume coupled with discrete element model (DEM‐2PFV). The structural dynamics was characterized by analyzing the pore volume and soil shrinkage curve obtained from numerically determined data. The soil hydraulic parameters were described using uni‐ and bimodal van Genuchten (vG) functions. The drainage simulations revealed hydro‐mechanical dynamics characterized by Braudeau‐shrinkage curve subdomains: The matrix‐only samples, with lower particle bond strength, exhibited relatively higher shrinkage. The coated samples, with higher particle stiffness and bond strength, displayed greater hydro‐mechanical stability. The numerically determined initial value of the saturated hydraulic conductivity (Ks) was about 70 times larger for matrix‐only samples than for coated samples. As expected, for the nonrigid soil structures, constant Ks, α, and n values for bimodal vG model resulted in prediction errors. Upscaling DEM‐2PFV pore‐scale model outcomes quantifies micro‐coating effects on macro hydro‐mechanics. This yields void ratio‐based soil water retention and hydraulic conductivity functions, advancing macroscopic soil hydraulic models and enhancing structured soil flow and transport descriptions.

Quantitative Visualization of Two‐Phase Flow in a Fractured Porous Medium

AbstractTwo‐phase fluid flow in fractured porous media impacts many natural and industrial processes but our understanding of flow dynamics in these systems is constrained by difficulties measuring the exchange of water between fracture and adjacent porous matrix. We present a novel experimental system that allows quantitative visualization of the air and water phases in a single analog fractured porous medium. The fracture system consists of a sintered‐glass porous plate in contact with an impermeable glass plate. A reservoir connected to the porous plate allows control of pore pressure within the porous medium. The fracture fills and drains through the porous matrix and flow manifolds along two edges of the fracture. The fracture is mounted in an imaging system that includes a controlled light‐emitting diode panel and a charge‐coupled‐device camera. Flow and pressure are controlled and monitored by a computer during experiments. To demonstrate this system, we carried out a series of cyclic drainage and imbibition experiments in fractures bounded by porous media with different pore‐size distributions in the porous matrix. Images of the drainage process demonstrate that the air‐water distribution within the fracture evolves differently than has been observed in non‐porous fractured systems. Specifically, we observed limited trapping of water within the fracture during drainage. Conversely, during imbibition, because air cannot exit through the porous matrix, significant regions of air became entrapped once pathways to the fracture boundaries became water filled. The differences in phase evolution led to substantial differences in the evolution of estimated relative permeability with saturation.

Impact of gas type on microfluidic drainage experiments and pore network modeling relevant for underground hydrogen storage

Underground hydrogen storage (UHS) in geological reservoirs is proposed as a technically feasible solution to balance mismatch between supply and demand in emerging markets. However, unique hydrogen properties and coupled flow mechanisms require new investigations to fully understand transport and storage of hydrogen in porous media across scales. Here we use microfluidics to investigate the effect of gas type and injection rate on flow patterns, saturation and connectivity of the gas phase. We visually observe that gas flow is characterized by capillary fingering, further confirmed by fractal dimension analysis. At lower injection rates, the gas saturation after drainage appears to increase with gas viscosity, with lower hydrogen saturation compared to methane and nitrogen. The maximum gas saturations (39–46 %) were achieved at higher injection rates, showing no clear correlation to gas type. However, the high-rate injections lead to undesired outcomes in terms of formation of disconnected gas ganglia, mostly pronounced for nitrogen. We identify an optimal injection rate to achieve maximum gas saturation with the least amount of disconnected gas. The experimental results are supported with pore network modeling to derive relative permeability and capillary pressure functions.

Phenolic compounds weaken the impact of drought on soil enzyme activity in global wetlands.

Soil enzymes play a central role in carbon and nutrient cycling, and their activities can be affected by drought-induced oxygen exposure. However, a systematic global estimate of enzyme sensitivity to drought in wetlands is still lacking. Through a meta-analysis of 55 studies comprising 761 paired observations, this study found that phosphorus-related enzyme activity increased by 38% as result of drought in wetlands, while the majority of other soil enzyme activities remained stable. The expansion of vascular plants under long-term drought significantly promoted the accumulation of phenolic compounds. Using a 2-week incubation experiment with phenol supplementation, we found that phosphorus-related enzyme could tolerate higher biotoxicity of phenolic compounds than other enzymes. Moreover, a long-term (35 years) drainage experiment in a northern peatland in China confirmed that the increased phenolic concentration in surface layer resulting from a shift in vegetation composition inhibited the increase in enzyme activities caused by rising oxygen availability, except for phosphorus-related enzyme. Overall, these results demonstrate the complex and resilient nature of wetland ecosystems, with soil enzymes showing a high degree of adaptation to drought conditions. These new insights could help evaluate the impact of drought on future wetland ecosystem services and provide a theoretical foundation for the remediation of degraded wetlands.

Detection and evaluation of anthropogenic impacts on natural forest ecosystems from long-term tree-ring observations

Anthropogenic interventions lead to various direct and indirect impacts on natural ecosystems that are often hindered by natural long-term variability, and thus their detection and evaluation remain challenging. Ecological systems are strongly affected by climate variations that typically exhibit long-term correlations capable of imitating or hindering external trends in finite-time observations, thus complicating their detection and correct attribution to either anthropogenic interventions or natural variability. Here we focus on the quantitative assessment of the alterations in the tree-ring width (TRW) of four tree species in response to the changes in the soil water regime following a drainage experiment in a dwarf-shrub type peatland forest. We consider the long-term effects of the intervention, focusing on two characteristic quantities: the durations of clusters when significant discrepancies with relevant controls could be observed in every single consecutive year, and relative trends in the data reflecting long-term, gradual changes in the ecosystem. By extrapolating pre-drainage TRW dynamics and adjusting for recent climate variations using a multivariate model, we simulate surrogate data series that act as additional controls for the post-drainage time period. By comparing the long-term dynamics of the observational TRW data series against both natural and surrogate controls over several decades following the drainage experiment, we evaluate long-term alterations and gradual trends in the tree growth dynamics and reassess the statistical significance of these effects, taking into account long-term correlations in the natural TRW variations. Our results also indicate pronounced alterations in the drought stress response characterized by significant negative trends in the tree growth dynamics following the 2010 heatwave and associated flash drought in the drained area, while no similar effect could be observed in the undrained area, indicating that the increased productivity of the forest ecosystem following the drainage likely comes at the cost of its reduced drought stress resilience.

Macropore flow in relation to the geometry and topology of soil macropore networks: Re-visiting the kinematic wave equation

The rapid flow of water through soil macropores significantly affects the partitioning of precipitation between surface runoff and infiltration and also the rate of solute transport in soil, both of which have an impact on the risk of contamination of surface water and groundwater. The kinematic wave equation is often employed as a model of gravity-driven water flow through soil macropores. The exponent in this simple model influences the pore water velocity attained in the macropores at any given input rate and is usually estimated by inverse modelling against measured flow rates or water contents. In theory, the exponent in the kinematic wave equation should depend on the geometry and topology of the conducting macropore networks, although these relationships have not so far been investigated. In this study, we related metrics of soil structure derived from X-ray images to values of the kinematic exponent estimated from drainage experiments on twenty-two columns sampled at three different field sites under two contrasting land uses and at three different depths.We found that smaller values of the exponent in the kinematic wave equation, which would equate to more rapid flow of water through soil macropores, were found in plough pan and subsoil columns of smaller macroporosity, for which biopores comprised a significant fraction. The macroporosity in these columns was more vertically oriented and poorly inter-connected, though still continuous across the sample. In contrast, topsoil columns from both arable land and grassland had better connected, denser and more isotropically-distributed macropore networks and larger values of the kinematic exponent. Our results suggest that for predictive modelling at large scales, it may be feasible to estimate the kinematic exponent using class pedotransfer functions based on pedological information such as land use and horizon type.

Rapid assessment of water phase trapping on gas permeability reduction in typical tight gas reservoirs in China

Water phase trapping (WPT) is one of the primary formation damage issues which can cause a steep drop in tight gas production. This paper presented a rapid assessment of the damage potential of WPT in Daniudi, Nanpu 5th, and Keshen 9th tight gas reservoirs involving shallow to ultra-deep layers in China. Typical core samples of the three tight gas reservoirs were selected to perform water imbibition and drainage experiments to mimic the WPT occurrence. After that, the damage degree to core gas permeability induced by WPT was evaluated. Results showed that, for a 16-h vertical water imbibition experiment, the core samples of Daniudi gas reservoir experienced the fastest water imbibition process while the core samples of Keshen 9th gas reservoir established the highest water saturation. After water removal, the ranges of damage degree to core gas permeability induced by the incremental water saturation were 36.07%–78.13%, 36.06%–56.21%, and 61.00%–76.30% in Daniudi, Nanpu 5th, and Keshen 9th tight gas reservoirs, respectively. It found that with the increasing formation depth, tight gas reservoirs can suffer greater damage from WPT not only because of the decline in rock permeability but also the salting out of high salinity formation water. In general, it holds that strong water capillary imbibition phenomenon, low water removal capacity, and high gas permeability damage degree are found to be the striking features of WPT potential on these typical tight gas reservoirs in China.

Displacement Patterns of a Newtonian Fluid by a Shear‐Thinning Fluid in a Rough Fracture

AbstractTwo‐phase flow involving non‐Newtonian fluids in fractured media is of vital importance in many natural processes and subsurface engineering applications, such as rock grouting, groundwater remediation, and enhanced oil recovery. Yet, how the displacement dynamics is impacted by the non‐Newtonian rheology remains an open question. Here, we conduct primary drainage experiments in which a shear‐thinning Xanthan gum solution displaces a silicone oil in a transparent rough fracture for a wide range of shear‐thinning property (controlled by polymer concentration) and flow rates. We first evaluate the effects of shear‐thinning property on displacement efficiency. Based on qualitative and quantitative analyses of the observed fluid morphologies, we present an experimental phase diagram of the obtained displacement patterns. We characterize a novel displacement pattern where the fluid‐fluid interface changes from stable (plug flow) to unstable (fingering) as the fracture aperture, averaged over the transverse direction, varies along the mean flow direction. We demonstrate that the existence of this mixed displacement pattern can be explained by local viscosity heterogeneity induced by the coupling of the shear‐thinning behavior and the spatial variability of apertures. Finally, we propose a theoretical model elucidating the mechanisms behind the flow regime transitions. The interface stability criterion predicted by this model exhibits good agreement with the experimental measurements, and stresses the potentially important role of fluid rheology, coupled to aperture variability, in immiscible displacements in rough fractures. These findings provide new insights into the dynamics of immiscible two‐phase flows with non‐Newtonian effects, and has potential implications for the aforementioned engineering applications.

Encoder–Decoder Convolutional Neural Networks for Flow Modeling in Unsaturated Porous Media: Forward and Inverse Approaches

The computational cost of approximating the Richards equation for water flow in unsaturated porous media is a major challenge, especially for tasks that require repetitive simulations. Data-driven modeling offers a faster and more efficient way to estimate soil moisture dynamics, significantly reducing computational costs. Typically, data-driven models use one-dimensional vectors to represent soil moisture at specific points or as a time series. However, an alternative approach is to use images that capture the distribution of porous media characteristics as input, allowing for the estimation of the two-dimensional soil moisture distribution using a single model. This approach, known as image-to-image regression, provides a more explicit consideration of heterogeneity in the porous domain but faces challenges due to increased input–output dimensionality. Deep neural networks (DNNs) provide a solution to tackle the challenge of high dimensionality. Particularly, encoder–decoder convolutional neural networks (ED-CNNs) are highly suitable for addressing this problem. In this study, we aim to assess the precision of ED-CNNs in predicting soil moisture distribution based on porous media characteristics and also investigate their effectiveness as an optimizer for inverse modeling. The study introduces several novelties, including the application of ED-CNNs to forward and inverse modeling of water flow in unsaturated porous media, performance evaluation using numerical model-generated and laboratory experimental data, and the incorporation of image stacking to account for transient moisture distribution. A drainage experiment conducted on a sandbox flow tank filled with monodisperse quartz sand was employed as the test case. Monte Carlo simulation with a numerical model was employed to generate data for training and validation of the ED-CNN. Additionally, the ED-CNN optimizer was validated using images obtained through non-intrusive photographic imaging. The results show that the developed ED-CNN model provides accurate approximations, addressing the high-dimensionality problem of image-to-image regression. The data-driven model predicted soil moisture with an R2 score of over 91%, while the ED-CNN optimizer achieved an R2 score of over 89%. The study highlights the potential of ED-CNNs as reliable and efficient tools for both forward and inverse modeling in the analysis of unsaturated flow.

Development of non-coagulable grout long-term sealing material for gas drainage

Gas is produced during coal formation and is a major threat to the safety of coal mining operations. Gas-related accidents, including gas explosions and coal and gas outbursts, are particularly dangerous. However, gas also has great potential as a clean energy source. Therefore, effective gas extraction is essential for preventing accidents and utilizing its potential. The sealing material used for gas extraction boreholes directly affects the quality of the seal and, consequently, the efficiency of gas extraction. To address the limitations of cement-based and polyurethane sealing materials, this paper presents a novel non-coagulant long-term sealing material. Firstly, the optimal material ratio was determined through experiments involving constant temperature and weightlessness. The optimum proportion of modifier to be added is obtained by constant temperature weight loss experiments. Secondly, microscopic analysis revealed that the modified component was effectively inserted into the group. To simulate the underground gas extraction conditions in coal mines, drainage and plugging experiments were designed. The results showed that the new material had a 100% plugging performance during the observation time, while the plugging performance of cement-based and polyurethane sealing materials significantly decreased under the same experimental conditions. Finally, the non-coagulant long-term sealing material was applied in the gas drainage experiment of tunnel 53081 at Changping Coal Mine. Compared to the original cement-based sealing material, the gas extraction concentration of the borehole increased by 16.5%. These results suggest that the newly developed sealing material is suitable for gas extraction and has significant potential for practical application.

Revisiting the definition of field capacity as a functional parameter in a layered agronomic soil profile beneath irrigated maize

The soil water content at the condition of field capacity (θFC) is a key parameter in irrigation scheduling and has been suggested to be determined by running a synthetic drainage experiment until the flux rate (q) at the bottom of the soil profile achieves a predefined negligible value (qFC). We question the impact of qFC on the assessment of field capacity. Moreover, calculating θFC as the integral mean of the water content profile when q is equal to qFC is strictly valid only for uniform soil profiles. By contrast, this practice is ambiguous and biased for stratified soil profiles due to the soil water content discontinuity at the layer interfaces. In this study, the concept of field capacity was revisited and adapted to practical agronomic heuristics. By resorting to the assessment of root-zone water storage capacity (W), we envision field capacity as a functional hydraulic parameter derived from synthetic irrigation scheduling scenarios to minimize drought stress, drainage, and nitrate leachate below the root zone. A functional analysis was carried out on a 135-cm-thick layered soil profile beneath maize in eastern Nebraska. On-farm irrigation scheduling applications and agricultural practices were recorded for 20 years (2001–2020) at a daily time step. Hydrus-1D was calibrated and validated with direct measurements of the soil water retention curve and soil water content data, respectively, in each soil layer. A set of functional field capacity values was derived from 24 irrigation scheduling scenarios, and the optimal water storage capacity at field capacity (WFC) was approximately 50 cm (corresponding to about 80% saturation in the soil profile). An average irrigation amount of 217.5 mm distributed over 21 events was obtained by using optimal irrigation scheduling, which was initiated when the matric pressure head took on a value of −700 cm and the irrigation rate was set at 1.0 cm d−1. This irrigation practice ensured water storage at approximately the same level (ideally at WFC) by sustaining only evapotranspiration fluxes in the uppermost portion of the root zone and by limiting excessive drainage. This protocol can be transferred to other agricultural fields.

Continuum and discrete element modelling for describing coupled hydro-mechanical effects of earthworm burrow coatings on soil shrinkage

Structured soils with earthworm burrows are locally heterogeneous due to coatings along these biopore walls that are superimposed on the inter- and intra-aggregate pore network of the soil matrix. The partially compacted finer-textured and organic matter-rich coatings can limit the flow exchange between the macropores and the soil matrix during preferential flow. Still unknown are dynamic hydro-mechanical interrelations in coating and matrix domains that affect stress–strain behaviour at the macroscopic scale. Such hydro-mechanic interactions may be described with the discrete element method (DEM) coupled with a two-phase pore finite volume (2PFV) approach if relevant pore structures are represented in the model. The objective was to develop a coupled DEM-2PFV model together with a parameterization procedure. Major task was to create a parameterization procedure to calibrate micro parameters of the model by macro properties quantified from drainage experiments of soil samples with earthworm burrow wall coatings.The solid phase was modelled by particle aggregation creating inter and intra-aggregate pore network for the soil matrix in a cube of about 5 cm edge length and one side with the coating structure. This DEM model was coupled with a 2PFV model to simulate hydro-mechanic effects during drainage. Sand box drainage experiments were carried out on soil matrix and biopore samples with laser surface elevation measurements to obtain the mechanical stress–strain macro parameters necessary for model calibration. The poly-dispersed DEM-2PFV model was able to describe effects of two-phase air–water flow on stress–strain macro parameters. The micro parameters (i.e., particle stiffness and bond strength) of the pore scale model were obtained from macro parameters of the primary and secondary stress–strain stages by training a random forest meta-estimator. The model was able to reproduce the pore network of coating material and the inter- and intra-aggregate pore network of the matrix that are dynamically changing with the effective stress. The machine learning model revealed that the bond strength among particles within aggregates governed the shrinkage of soil matrix, while the particle stiffness of the coating material reduced the susceptibility of aggregate breakage producing a more stable inter-aggregated pore network during the drainage process. This study confirmed that coating material present in biopore surface increases the horizontal soil hydro structural stability. The microscale hydro-mechanic modelling can be useful for finding flow exchange parameters inputs for upscaled models and correlating pore-scale parameters to experimentally determined stress–strain macro parameters.

Abstract 4614: Investigating lymphatic vessel remodeling and anti-tumor immunity in pancreatic cancer using tumor-on-chip and mouse models

Abstract Pancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest tumors in humans. PDAC has an immunosuppressive tumor microenvironment, constituting for poor immunotherapy outcomes. Lymphatic vessels (LVs) transport leukocytes and antigens from tumor peripheries to draining lymph nodes (dLNs) for activation of anti-tumor immune responses. It is believed that impairment of the lymphatic function may result in delayed and ineffective immune activation against tumors. In this study, we created a three-dimensional (3D) tumor-on-chip model to examine phenotypical and functional changes in 3D engineered LVs, composed of human primary lymphatic endothelial cells (LECs) in co-culture with PDAC cells. Our in vitro studies revealed that PDAC cells induce lymphangiogenesis and tighten cell-cell junctions in LECs, forming “zipper-like” LEC junctions, compared to control LECs with “button-like” junctions. We introduced 70kDa dextran into the LV lumens and showed PDAC-induced zippering of junctions decreased vessel permeability. These results led us to hypothesize that altered LEC junctions may affect fluid drainage into the LVs in vivo. We inoculated PDAC cells into the mouse ear pinnae and performed whole-mount immunostaining and lymphatic drainage experiment by injecting Evans blue into the ears and measured the remained Evans blue in the ears. In the ear experiments, inoculated PDAC cells affected host LVs with originally button-like junctions to become zipper-like and impede lymphatic drainage. To identify a potential signaling pathway that may be responsible for LEC junction zippering, we used phospho-kinase arrays and discovered that PDAC cells induced LECs to increase phosphorylation of GSK3-β, JNK kinases, and enhanced the total protein level of β-catenin, implying that PDAC cells turned on the WNT signaling in LECs. In preliminary screening, we treated LECs co-cultured with PDAC cells with WNT-C59, an WNT inhibitor that blocks secretion of all WNT ligands, which resulted in decreased number of LV sprouting and less contractile actin-cytoskeleton in LECs. It is critical to know which molecules were secreted by PDAC cells and influenced the WNT signaling in LECs. With that in mind, we plan to perform mass spectrometry with PDAC-conditioned media to identify PDAC-specific secretome; and run RNA-seq with LECs isolated from mouse ears with or without PDAC to investigate molecular basis of the WNT activation in LECs and LV remodeling. Finally, we plan to examine the egress of leukocytes from primary PDAC tumor site, T cell activation in tumor-dLNs, and PDAC tumor growth with or without WNT inhibition in Kaeda mice. The identity and function of PDAC-egressed immune cells, and those which stayed within the primary tumor will enhance our understanding of the roles of LVs in orchestrating anti-tumor immunity in PDAC. Citation Format: Anna Maria Kolarzyk, Conor Loy, Renhao Lu, Iwijn De Vlaminck, Deborah Fowell, Esak Lee. Investigating lymphatic vessel remodeling and anti-tumor immunity in pancreatic cancer using tumor-on-chip and mouse models. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4614.

Characterization of two-phase flow in a faulted sandstone

Fault zones present in some underground CO2 storage formations can impact on injectivity, storage capacity, and the path taken by migrating CO2, including possible leakage to overlying formations and the escape of a plume beyond the area of a demarcated storage lease licence. A thorough understanding of the 2-phase flow in fault zones is therefore essential to de-risk any storage location where faults could be present. Many previous studies have addressed top-seal risks from fault reactivation, but the influence of intra-reservoir faults on flow within the target storage formations has received less attention. Studies of intraformational faults in sandstones have typically used plugs cored from outcrops or from subsurface boreholes, where important aspects of the geological history such as the stress conditions during faulting, and the degree of post-faulting compaction and cementation may be poorly constrained. Moreover, only intact fault rocks can be cored and re-loaded under stress with this approach, so that it is very difficult to establish the interacting effects or rock fractures and cataclastic gouge in a single experiment using borehole/outcrop samples.This study investigates newly created fault rock in sandstone that has been deformed under controlled conditions and without the effects of secondary cementation. We used a large direct shear rig to deform a large, water-saturated Bentheimer sandstone block to sufficient displacement (40mm) and under enough overburden pressure (25 MPa) to create a zone of cataclastic gouge several mm thick bounded by a damage zone of fractured rock. The sheared block was cored at an inclined angle while deep frozen to extract an oriented plug containing a complete and intact section of fault rock that could be reloaded under hydrostatic conditions in an x-ray transparent core holder. The faulted plug of Bentheimer was used for running steady-state drainage and imbibition 2-phase flow experiments. The fluid saturation and its spatial distribution in 3D inside the faulted plug were dynamically monitored during all stages of the experiment in a medical x-ray CT scanner.Analysis of the flow patterns revealed from the X-ray CT images collected over time enables us to characterize in detail, the influence of recently formed fault core and damage zones on fluid flow both during drainage as gas breaks across the fault zone, and as water re-invades during imbibition. The fault core acts as a semi-permeable membrane that is only permeable to the wetting phase (water) under pressure differentials less than the capillary entry pressure (Pce) of the membrane. During drainage stages, the high Pce of the fault core led to backfilling of the upstream end of the core and almost to compartmentalization of the sample. The fracture network that exists in the damage zone played a critical role in keeping the upstream side of the fault core connected to the downstream side. During imbibition stages, the high Pce of the fault core led to significant gas trapping at the upstream side of the fault core adjacent to the fault core-damage zone interface. While the fault core formed a barrier to flow, the fracture network can provide bypass pathways for gas flow. In this particular sample bypassing through fractures was sufficient such that for a particular value of average gas saturation the flow rate was faster in the faulted rock than in the unfaulted reservoir rock.

Inverse estimation of hydraulic parameters of soils with rock fragments

The application of inverse modeling to determine the hydraulic properties of layered soils with rock fragments (RF > 2 mm) is associated with complex challenges such as selecting suitable hydraulic functions and defining a strategy to optimize many parameters. These two issues were addressed in this study by performing field drainage experiments in layered soil profiles (three layers) with different particle size distributions and different percentages of RF. Water contents (θ) and pressure heads (h) were monitored at different soil depths during drainage experiments (h ≥ −200 cm). Data of θ and h for a drier range (h < −5000 cm) were determined with a dew point potentiometer on disturbed soil samples. The unimodal and bimodal van Genuchten-Mualem functions were evaluated, and their parameters were optimized using the Hydrus-1D “Inverse solution”. The RETC curve fitting software was used to estimate the second set of parameters of the bimodal function. The parameters for the uni- and bimodal models (15 and 27 parameters, respectively) were repeatedly optimized by fixing some parameters while estimating others. The unimodal van Genuchten-Mualem function provided a satisfactory fit of θ and h measurements only when either drainage or dew point potentiometer measurements were used. On the other hand, the bimodal van Genuchten-Mualem function provided a satisfactory fit of θ and h measurements when both sets of data (drainage and dew point potentiometer measurements) were used simultaneously. Furthermore, the optimized parameters were physically consistent except for a few high saturated hydraulic conductivity values. Therefore, bimodal functions should be considered to represent the hydraulic properties of soils with RF. The problem of many calibrated parameters when using bimodal functions can be managed using sequential optimization, which allowed us to estimate 27 parameters for layered soils with RF successfully.