Table Position Research Articles

Investigations of Silty Soil Slopes under Unsaturated Conditions Based on Strength Reduction Finite Element and Limit Analysis

Matric suction plays a key role in slope stability by conferring an apparent cohesion component to the unsaturated portion of the soil. This paper adopts the total cohesion method to investigate the contribution of apparent cohesion on the stability of silty slopes under hydrostatic conditions. Phase2 and Optum G2 numerical programs, based on strength reduction finite element analysis and finite element limit analysis methods, respectively, are used for numerical analysis. Generally, Phase2 and Optum G2 results are in good agreement with each other. Optum G2 yields slightly higher factor of safety results than Phase2, particularly for steep slopes β≥ 30°. The results are presented in form of stability charts which are validated with a case from a previous study. Notably, the contribution of apparent cohesion to unsaturated shear strength is most pronounced when varying the water table. An examination of the slope failure mechanism reveals that the toe failure mechanism is the dominant failure mechanism. The depth of the failure surface is most sensitive to changes in the slope angle, cohesion and water table position. The influence of the air-entry value on the depth of the failure surface is contingent upon the location of the water table.

A mathematical model of a brushed DC motor system

Mathematical model has been proposed for some system that involves a brushed DC motor and it is widely used in industry. Brushed DC motor ideals for applications with a low- torque, manage to change pace or speed and it is widely used in many applications such as x-y table positioning system, conveyor systems and other system that required to use the features that brushed DC motor have. Mathematical model of brushed DC motor in order to verify the performance of the DC motor. In this paper, mathematical model of brushed DC motor will be derived from a brushed DC motor circuit that consist of two parts that are electrical and mechanical part. To validate the functionality of mathematical model, the performance of the brushed DC motor without any controller will be compared with the brushed DC motor with the presence of PI-PD controller that will be tuned by trial-and-error method. Performances of both brushed DC motor with and without controller will be compared in terms of transient response which are, rise time, Tr, settling time, Ts, steady state error, ess and lastly percentage overshoot. At the end of the study, the brushed DC motor with PI-PD controller show a better performance compared to the brushed DC motor without any controller.

Simulation of Unconfined Aquifer Flow Based on Parallel Adaptive Mesh Refinement

AbstractThe density of a numerical mesh is a key component for the quality of the numerical solution. Common methods in groundwater simulations rely on meshes generated prior to simulation, which lead to unnecessary or insufficient degrees of freedom (dofs). In this study we use Adaptive Mesh Refinement (AMR) to substitute the subjective mesh generation process with a more rigorous approach where new dofs are iteratively added to the solution of an initial coarse mesh based on a solution error estimation. The simulation is solved on a succession of meshes through which the mesh density is increased in areas of steep gradients in the solution variable. Here, we apply the approach to unconfined aquifer flow which is a non‐linear problem commonly encountered in groundwater modeling. By taking advantage of the iterative nature of AMR we arrive at an efficient solver approach. We treat the position of the unconfined boundary as an additional unknown which is estimated iteratively. The first iterations are executed rapidly as the mesh is rather coarse, while the free boundary adapts to the computed water table position as close as the mesh density allows. In this study we demonstrate the viability of the proposed unconfined aquifer simulation method to a series of 2D hypothetical examples under several conditions and stresses as well as a 3D test case. In all cases the AMR was able to automatically resolve the solution in areas with steep hydraulic head gradient, using appropriately higher density to achieve high localized refinement and accuracy.

Numerical Modelling Observations of Settlement for Pad Footings Supported on Soft Clay Soil

Settlement calculation is an important part in the design of shallow foundations resting on soft soils. The size of the foundation, the depth of the footings, and the rise in ground water level are thought to influence settlement and have been the subject of much research for many years. Thus, this study compared several pad footing sizes using numerical techniques as the basis. The first objective of this study was to analyse soil and pad footing settlement, and to determine the optimal size of footing that withstands excessive settlement due to variation in the water table and the depth of the foundation. Three footing embedment depths of 1.5, 2, and 3m with three water table positions, at the GL (0m), 1.5, and 3m with an applied foundation concentrated load of 440 kN using five footing models of 1.5mx1.5m, 2mx1.5m, 2 m x 2 m, 2.5x1.5m, and 2.5x1.5m pad footing with a uniform thickness of 0.5m were considered. In this study, a 3D Plaxis simulation is used for predicting the settlement of shallow foundations on soft clay soils. Settlement results were discovered at various water table positions and foundation depths. The study found that the 2.5x2m footing was deemed the best among the simulated foundations, and the 3m foundation embedment was considered the best at shallow depths due to less excessive settlement than the other tested foundations. The settlement had a significant impact on the size of the foundation and the depth of the footing. The depth of the water table has a small impact on the settlement. Parametric analysis is also being used to gain a better understanding of the behaviour of the elastic settlement of various shallow foundations. It is found that the footing area increases, settlement decreases and vice versa.

Processing Algorithm of Irregular Table Image in Tobacco Package Based on Dual-coding Difference of Gaussians Method

Objectives: Currently, in a large number of print-out report documents from tobacco package, there exist irregular phenomena such as discontinuous vertical lines, misplaced frame lines and multi-page tables. Thus, the existing table recognition algorithm cannot be adopted to perform digital identification. In order to solve this problem, this paper proposes a table image processing algorithm based on the dual-coding difference of Gaussians iterative clustering. Firstly, the method of local regional sub-block is used to the skew correction threshold to conduct image correction. Secondly, the corrected images are coded by rows and columns, and 2D image features are transformed into 1D image features. Thirdly, the Gaussian differenced operation is adopted to obtain effective characteristic matrices that are stable and easily distinguishable. Then the iterative clustering analysis is performed to obtain the feature values of effective frame lines. Fourthly, after finishing the tasks, such as the table positioning, inner structure reconstruction, and text information identification, the dichotomy judgmentsof the integrity of multi-page tablesare realized according to the local pixel features. Finally, the text information inside the local regions and the reconstructed regions are merged, and the digital reproduction of the multi-page tables is realized. To validate the effectiveness of the proposed algorithm, an experiment in the sample set containing 12,840 table images with different resolutionsis carried out. The average detection accuracies of table positioning, table cell reconstructionand multi-page incompleteness are 98.95%, 99.80%, and 95.85%, respectively. The experimental results show that the proposed algorithm is simple and effective, and can accomplish the digital reproduction of irregular tables.

Hummock-scale controls on groundwater recharge rates and the potential for developing local groundwater flow systems in water-limited environments

We use two-dimensional numerical models to identify controls on groundwater recharge, water table dynamics, and the sink-source function of fine-textured hummocks in water-limited environments. A silty clay loam hummock with aspen forest cover in the sub-humid Boreal Plains region of Canada is used to develop a conceptual model and calibrate a variably-saturated flow model to better investigate the dynamics of recharge, water table position, and lateral flow between the forested hummock and adjacent peatland. Scenario testing (achieved by raising and lowering the hydraulic conductivity by an order of magnitude and altering the hummock height and length) provides further understanding of the controls that hydraulic conductivity and hummock morphometry exert on recharge and forestland-peatland interactions. We find that the hydraulic conductivity of the glacial till has the largest control over recharge, followed by the hummock height and length and, lastly, annual atmospheric fluxes. Hummocks with higher hydraulic conductivity or long morphometric profiles are most often sinks of water as they promote increased root-water uptake, while taller hummocks with lower hydraulic conductivity tend to act as hydrologic sources for adjacent wetlands. The magnitude of annual recharge and water table elevation are poorly correlated with annual atmospheric fluxes due to the strong effects of multi-year storage deficits or surpluses; however, they are appreciably affected by decadal wet-dry cycles typical of the Boreal Plains climate. Additionally, we show that both distance along a hummock and elevation are key factors in controlling the spatial distribution of recharge at a single hummock. It is common to conceptualize the water table as a shallow and subdued replica of surface topography, where water flows from topographic highs (i.e., forestlands) to topographic lows (i.e., peatlands) in humid environments; however, as we show here, recharge rates, water table elevation, and the sink-source function of a forested hummock in water-limited environments is highly variable in time and space, and strongly dependent on both the hydrogeological and morphometric properties of the hummock.

This Month in Adult Urology

This Month in Adult Urology

The doctor will see you now: eye gaze, conversation and patient engagement in the surgical outpatient clinic. An Australian observational cross-sectional study.

Surgical outpatient consultations are demanding for the surgeon and patients without a definite formula for success. Various factors have been identified regarding factors that influence patient satisfaction and engagement. We aimed to examine the modern-day surgical outpatient consultation and report on these factors. An observational cross-sectional study was performed by reviewing video recordings of 182 surgical consultations by 12 surgeons at The Queen Elizabeth Hospital, South Australia, Australia. The mean consultation time was 12.3min, with pre-surgical consultations being the longest. There were 107 consultations for benign conditions (58%). Proportionally, the consultant spoke most (51.9% of total consultation time), followed by the patient (19.5%) and then companion (8.2%). Forty-eight (26.4%) patients brought a companion to the clinic but monopolisation of the consultation by the companion was rare. When a companion was present, there was more mutual eye gaze between the consultant and the patient. Interruptions were present in 23.6% of consultations and were associated with a significant increase of the length of the consultation. Table positioning did not seem to affect the dynamics of the outpatient consultation. Companions are highly valuable for promoting patient engagement and their presence should be encouraged in surgical outpatients. Interruptions should be kept to a minimum to avoid unnecessary delays. Further studies should be conducted to investigate the effect of companions, interruptions and table positioning during a consultation on patient outcomes.

Acceleration-based disturbance compensation for elastic rack-and-pinion drives

Rack-and-pinion drives are mainly used for large machine tools and are often operated with indirect position control. Due to the lack of state information on the output side, this results in reduced accuracy regarding the table position. In addition, the system can only react inadequately to disturbances outside the control loop, meaning that often insufficient results can be achieved in typical application scenarios such as milling. To meet the increasing dynamic and accuracy requirements of the modern manufacturing industry, this paper presents a highly dynamic acceleration-based disturbance compensation method. For this purpose, the table acceleration is estimated using a dynamical model of the drive train and compared to the signal from an additional acceleration sensor attached to the machine table. Based on the resulting difference, an additional compensation torque is provided, which suppresses the disturbance in counterphase. The approach is tested experimentally on an open control platform with industrial drive components and the behavior is investigated based on compliance frequency responses and externally applied milling forces. At the same time, a standardized parametrization methodology is developed and the robustness is evaluated by varying table masses. In summary, a considerable improvement of the dynamic disturbance behavior can be achieved compared to the conventional system without compensator.

Acceptance procedure for the linear accelerator component of the 1.5 T MRI-linac.

PurposeTo develop and implement an acceptance procedure for the new Elekta Unity 1.5 T MRI‐linac.MethodsTests were adopted and, where necessary adapted, from AAPM TG106 and TG142, IEC 60976 and NCS 9 and NCS 22 guidelines. Adaptations were necessary because of the atypical maximum field size (57.4 × 22 cm), FFF beam, the non‐rotating collimator, the absence of a light field, the presence of the 1.5 T magnetic field, restricted access to equipment within the bore, fixed vertical and lateral table position, and the need for MR image to MV treatment alignment. The performance specifications were set for stereotactic body radiotherapy (SBRT).ResultsThe new procedure was performed similarly to that of a conventional kilovoltage x‐ray (kV) image guided radiation therapy (IGRT) linac. Results were acquired for the first Unity system.ConclusionsA comprehensive set of tests was developed, described and implemented for the MRI‐linac. The MRI‐linac met safety requirements for patients and operators. The system delivered radiation very accurately with, for example a gantry rotation locus of isocenter of radius 0.38 mm and an average MLC absolute positional error of 0.29 mm, consistent with use for SBRT. Specifications for clinical introduction were met.

Wetland Heterogeneity Determines Methane Emissions: A Pan-Arctic Synthesis.

Methane (CH4) emissions from pan-Arctic wetlands provide a potential positive feedback to global warming. However, the differences in CH4 emissions across wetland types in these regions have not been well understood. We synthesized approximately 9000 static chamber CH4 measurements during the growing season from 83 sites across pan-Arctic regions. We highlighted spatial variations of CH4 emissions corresponding to environmental heterogeneity across wetland types. CH4 emission is the highest in fens, followed by marshes, bogs, and the lowest in swamps. This gradient is controlled by the water table, soil temperature, and dominant plant functional types and their interactions. The water table position for maximum CH4 emission is below, close to, and above the ground surface in bogs, marshes/fens, and swamps, respectively. The temperature sensitivity (Q10) of CH4 emissions varied among different wetland types, ranging from the lowest in swamps to the highest in fens. The interactive impact of temperature and the water table positions on CH4 emissions are regulated with dominant plant functional types. CH4 emissions from wetlands dominated by vascular plants rely more on species composition than that dominated by non-vascular plants. Wetlands with greater abundance of graminoids (e.g., fens) have higher CH4 emissions than tree-dominated wetlands (e.g., swamps). This synthesis emphasizes the role of wetland heterogeneity in determining the strength of CH4 emissions.

Thermo-hydraulic and sensitivity analyses on the thermal performance of energy tunnels

The efficiency of energy tunnels depends on the ground properties and ambient environment. Another factor that noticeably influences the process is the groundwater supply availability. The design strategy and assessment method may require careful consideration or even adjustment when significant groundwater movements are present. This study provides evidence for assessing thermal exploitation based on parameters in relation to different subsoil conditions. A numerical parametric study based on a Metro Torino line 1 section is performed, followed by deterministic and sample-based sensitivity analyses to determine the relative impacts of different hydraulic and thermal variables on the energy tunnel thermal performance. Results demonstrate that the importance of the groundwater flow direction and velocity on thermal efficiency highly depends on the water table position. Maximum performance improvements of respectively 149%, 127% and 49% can be achieved due to variations of the water table position, water flow velocity and water flow direction in this study. For a long thermally activated tunnel, a water flow parallel to the tunnel axis makes the downstream-most ring approximately 50% less efficient than the upstream-most ring. The temperature difference between the undisturbed ground and the pipe inlet is defined as the most sensitive parameter to the thermal performance of an energy tunnel when the water table is lower than the tunnel lining bottom.

A comparison of plant communities and water chemistry at Sandhill Wetland to natural Albertan peatlands and marshes

Plant communities and water chemistry properties were characterized at Sandhill Wetland; an experimental reclamation site constructed above a backfilled open pit mine in northeastern Alberta, Canada. Observations from the reclamation site were compared to 12 mature reference wetlands (10 fens and 2 marshes) to determine the type of natural wetland the site most closely resembles at its current successional stage. From this survey of 20 research plots distributed across Sandhill Wetland, 44 plant species were encountered (35 vascular plants and 9 bryophytes). Using multivariate approaches, diversity indices, and coefficient of conservatism values, results indicate areas with water levels above the soil surface at Sandhill Wetland are most comparable to regional marshes, with Typha latifolia and Carex aquatilis exhibiting the highest cover. Across the wetland periphery where water levels are several centimeters below the soil surface, plant communities were quite dissimilar from the reference sites and dominated by the grass Calamagrostis canadensis. Based on principle components analysis, we show water chemistry at Sandhill Wetland is in a state that is between marshes and saline fens. Sandhill Wetland overall possesses a unique set of structural and chemical features in the sixth year of development. In areas where water levels are above the soil surface there is potential for development into a slightly brackish marsh analogue. The successional trajectory of low water table position areas is somewhat uncertain as the wetland periphery exhibited mixed characteristics resembling those of wet meadow, riparian, and upland environments, which we did not survey.

Structural response of non-perforated and perforated corrugated high-density polyethylene pipes under variable loading

The structural response of small diameter (<300 mm) corrugated high-density polyethylene (HDPE) drainage pipes installed on agricultural lands, has not been thoroughly examined. Additionally, characteristics of imposed wheel loads from agricultural field machinery are not adequately represented in conventional structural design practises for buried pipes. This study investigates the response of single-wall corrugated HDPE pipes (100 mm diameter) under loading from 12 agricultural soil textures, two water table positions, and three agri-machinery wheel loads using a finite-element-based numerical model. Effects from two friction conditions (smooth and bonded) at the soil-pipe interface were assessed. Simulations were also done to determine the impact of variable perforation characteristics (shape, size, and configuration) on the stress distribution and deformation of the corrugated pipes. The results show that bonded friction conditions generally induce larger stresses in the pipe wall than smooth friction conditions, but the differences are not statistically significant across all soil and load types. The critical load case occurs for a loaded grain wagon on silt loam soils. The results also indicate that perforations in the pipe wall induce high stress concentrations at the edges of rectangular slots and circular holes, increasing the risk for failure by ductile yielding. Specifically, corrugated HDPE pipes perforated with 5.6 mm diameter holes produce stresses that exceed the yield strength at buried depths shallower than 0.9 m. In conclusion, perforation characteristics should be considered when assessing the structural adequacy of corrugated HDPE pipes for land drainage.

Room staff radiation dose in a vascular surgery hybrid operating room and evaluation of a real-time radiation dosimeter

Abstract Objective Real-time radiation dosimeter have been shown to decrease radiation exposure of the staff. This effect is mainly explained by increased awareness of the radiation due to direct radiation exposure feedback to the operator. We aimed to measure the radiation exposure of all staff members working in a hybrid operating room and wanted to compare the equivalent doses of real-time radiation dosimeters with thermoluminescence dosimeters. Methods Prospective non-randomized comparative trial. From April – October 2019, all staff members working in a hybrid operating room were equipped with real-time radiation dosimeters (Unfors RaySafe i3). The table positions of all staff members were documented. In addition, the first operator was equipped with a thermoluminescence Hp(3) eye lens dosimeter (TLD) placed outside the lead glasses to validate the real-time radiation dosimeter. Results The median dose of the operator / the first assistant was 73.6 µSv / 21.8 µSv for EVAR (n = 30); 57.25 µSv / 18.2 µSv for TEVAR (n = 23); 207.0 µSv / 76.65 µSv for more complex aortic procedures (f/bEVAR etc.; n = 15); 14.85 µSv / 8.5 µSv for occlusive disease of the iliac arteries (n = 27) and 6.1 µSv / 3.4 µSv for occlusive disease of the peripheral arteries (n = 53). The anesthesiologist’s median dose was 0.3 µSv, with highest values in f/bEVAR (3.9µSv). The scrub nurse’s median dose was 2 µSv with highest values in f/bEVAR (24 µSv). The position of any staff member at the left arm for transbrachial cannulation in f/bEVAR was associated with higher median equivalent radiation doses compared to the right femoral position (272.5 vs. 207 µSv for the operator (p=ns), 175.3 vs. 27.8 µSv for the first assistant (p = 0.027) and 45.55 vs. 8.0 µSv for the scrub nurse (p = 0.14)). The equivalent doses of the TLD and RaySafe did not correlate well using simple lineal regression analysis (r2 0.1713, p = 0.0014). Conclusion With the RaySafe real-time radiation dosimeter, table positions with increased radiation exposure can be identified. This allows for improvement in shielding at these positions, possibly leading to lower radiation exposure of the staff.

The relationship between team ability and home advantage in the English football league system

The existence of home advantage (HA) has been found in a variety of team sports including football. There is a paucity of research on the relationship between team ability and HA in domestic football leagues and the findings of previous studies are inconclusive. Using longitudinal data from the top four football divisions in England, this study investigates the influence of team ability on the HA of teams. The data collected for this study spans 24 seasons from 1995/96 to 2018/19 and includes 48,864 matches from the English Premier League (n = 9120), the Championship (n = 13,248), League One (n = 13,248) and League Two (n = 13,248). Team ability was interpreted in two ways: (1) the division in which teams play and (2) their league table position within each division. For both the divisional and positional analysis, HA was calculated as the ratio of home points to total points achieved by teams in each season under review. Evidence of a statistically significant HA was found in all four divisions and for teams of all abilities within each division. Small but statistically significant differences in HA were observed between divisions and between high, moderate and low ability teams within divisions.

How we assess mathematics degrees: the summative assessment diet a decade on

Abstract Two previous studies mapping university mathematics students’ summative assessment diet in the UK revealed a clear picture. In general, there was a dominance of closed book examinations with a strong relationship to departmental league table position. The decade since then has seen many changes in higher education in the UK, particularly in the strength of the student voice. The study we report here replicated the earlier work to see if there has been an impact on the assessment diet. While the analysis shows a very small decrease in the use of closed book examinations, this may be accounted for by the addition of adjunct modules, rather than a broadening of the assessment diet across mainstream mathematics topics.

Rotational positional error-corrected linear set-up margin calculation technique for lung stereotactic body radiotherapy in a dual imaging environment of 4-D cone beam CT and ExacTrac stereoscopic imaging.

Accurate calculation of set-up margin is a prerequisite to arrive at the most optimal clinical to planning target volume margin. The aim of this study was to evaluate the compatibility of different on-board and in-room stereoscopic imaging modalities by calculating the set-up margins (SM) in stereotactic body radiotherapy technique accounting and unaccounting for rotational positional errors (PE). Further, we calculated separate SMs one based on residual positional errors and another based on residual + intrafraction positional errors from the imaging data obtained in a dual imaging environment. A total of 22 lung cancer patients were included in this study. For primary image guidance, four-dimensional cone beam computed tomography (4-D CBCT) was used and stereoscopic ExacTrac was used as the auxiliary imaging. Following table position correction (TPC) based on the initial 4-D CBCT, another 4-D CBCT (post-TPC) and a pair of stereoscopic ExacTrac images were obtained. Further, during the treatment delivery, a series of ExacTrac images were acquired to identify the intrafraction PE. If a, b and c were the observed translational shifts in lateral (x-axis), longitudinal (y-axis) and vertical direction (z-axis) and α, β and γ were the rotational shifts in radians about the same axes, respectively, then the resultant translational vectors (A, B and C) were calculated on the basis of translational and rotational values. Set-up margins were calculated using residual errors post-TPC only and also using intrafraction positional errors in addition to the residual errors. Residual and residual + intrafraction SM were calculated from a dataset of 82 CBCTs and 189 ExacTrac imaging sessions. CBCT-based mean ± SD shifts in translational and rotational directions were 0.3 ± 1.8mm, 0.1 ± 1.8mm, - 0.4 ± 1.6mm, 0.1 ± 0.4°, 0.0 ± 1.0° and 0.3 ± 0.7°, respectively, and for ExacTrac - 0.1 ± 1.8mm, 0.2 ± 2.4mm, - 0.6 ± 1.8mm, 0.1 ± 1.2°, - 0.2 ± 1.3° and - 0.1 ± 0.6°, respectively. Residual SM without considering the rotational correction in x, y and z directions were 5.0mm, 4.5mm and 4.4mm; rotation-corrected SM were 4.4mm, 4.0mm and 5.5mm, respectively. Residual plus intrafraction SM were 5.5mm, 6.6mm and 6.2mm without considering the rotational corrections, whereas they were 5.0mm, 6.3mm and 6.2mm with rotational errors accounted for. Accurate calculation of set-up margin is required to find the clinical to planning target volume margin. Primary and auxiliary imaging margins fall in the range of 4.0 to 5.5mm and 5.0 to 7.0mm, respectively, indicating a higher SM for X-ray-based planar imaging techniques over three-dimensional cone beam images. This study established the degree of mutual compatibility between two different kinds of widely used set-up imaging modalities, on-board CBCT and in-room stereoscopic imaging ExacTrac. It also describes the technique to calculate the residual and residual plus intrafraction SM and its variation in a dual imaging environment accounting for rotational PE in stereotactic body radiotherapy of lung.

Water table rise in urban shallow aquifer with vertically-heterogeneous soils: Girinskii’s potential revisited

ABSTRACT Seepage through an aquifer, the hydraulic conductivity of which varies vertically, is studied using the Dupuit-Forchheimer approximation (Girinskii’s potential) and numerically by FDM-MODFLOW and FEM-HYDRUS-2D. In urban water hydrology, the effect of compaction of the top stratum of an aquifer on the flow rate and the position of the water table (characterized by an integral quantity of the saturated/dry area) is analysed. The area of the saturated zone is evaluated as a function of the conductivity ratio of the two strata, and their thicknesses. Conductivity varying linearly and exponentially is also analytically studied. Boundary-value problems are solved for a linear (nonlinear) ordinary differential equation if the evaporation rate is constant (decreasing exponentially with depth). The MODFLOW and HYDRUS-2D simulations give consistent fields of the piezometric head, pressure head, and Darcian velocity, as well as the water table position, which may have a global minimum (watershed).

Peat depth as a control onSphagnummoisture stress during seasonal drought

AbstractPeatlands are globally important long‐term sinks of carbon, however there is concern that enhanced peat decomposition and moss moisture stress due to climate change mediated drought will reduce moss productivity making these ecosystems vulnerable to carbon loss and associated long‐term degradation. Peatlands are resilient to summer drought moss stress because of negative ecohydrological feedbacks that generally maintain a wet peat surface, but where feedbacks may be contingent on peat depth. We tested this ‘survival of the deepest’ hypothesis by examining water table (WT) position, near‐surface moisture content, and soil water tension in peatlands that differ in size, peat depth, and catchment area during a summer drought. All shallow sites (&lt;40 cm depth) lost their WT (i.e., the groundwater well was dry) for considerable time during the drought period. Near‐surface soil water tension increased dramatically at shallow sites following WT loss, increasing ~5–7.5× greater at shallow sites compared to deep sites (≥40 cm depth). During a mid‐summer drought intensive field survey, we found that 60–67% of plots at shallow sites exceeded a 100 mb tension threshold used to infer moss water stress. Unlike the shallow sites, tension typically did not exceed this 100 mb threshold at the deep sites. Using species dependent water content – chlorophyll fluorescence thresholds and relations between volumetric water content and WT depth, Monte Carlo simulations suggest that moss had nearly twice the likelihood of being stressed at shallow sites (0.38 ± 0.24) compared to deep sites (0.22 ± 0.18). This study provides evidence that mosses in shallow peatland may be particularly vulnerable to warmer and drier climates in the future, but where species composition may play an important role. We argue that a critical ‘threshold’ peat depth specific for different hydrogeological and hydroclimatic regions can be used to assess what peatlands are especially vulnerable to climate change mediated drought.