Model for predicting resilient modulus of unsaturated subgrade soil using soil-water characteristic curve

2015 ◽  
Vol 52 (10) ◽  
pp. 1605-1619 ◽  
Author(s):  
Zhong Han ◽  
Sai K. Vanapalli
Keyword(s):  
Moisture Content ◽  
Soil Water ◽  
Resilient Modulus ◽  
Characteristic Curve ◽  
Optimum Moisture Content ◽  
Model Parameters ◽  
Soil Water Characteristic Curve ◽  
Subgrade Soils ◽  
Fine Grained ◽  
Proposed Model

Soil suction (ψ) is one of the key factors that influence the resilient modulus (MR) of pavement subgrade soils. There are several models available in the literature for predicting the MR–ψ correlations. However, the various model parameters required in the existing models are generally determined by performing regression analysis on extensive experimental data of the MR–ψ relationships, which are cumbersome, expensive, and time-consuming to obtain. In this paper, a model is proposed to predict the variation of the MR with respect to the ψ for compacted fine-grained subgrade soils. The information of (i) the MR values at optimum moisture content condition (MROPT) and saturation condition (MRSAT), which are typically determined for use in pavement design practice; (ii) the ψ values at optimum moisture content condition (ψOPT); and (iii) the soil-water characteristic curve (SWCC) is required for using this model. The proposed model is validated by providing comparisons between the measured and predicted MR–ψ relationships for 11 different compacted fine-grained subgrade soils that were tested following various protocols (a total of 16 sets of data, including 210 testing results). The proposed model was found to be suitable for predicting the variation of the MR with respect to the ψ for all the subgrade soils using a single-valued model parameter ξ, which was found to be equal to 2.0. The proposed model is promising for use in practice, as it only requires conventional soil properties and alleviates the need for experimental determination of the MR–ψ relationships.

scholarly journals Integrated approaches for predicting soil-water characteristic curve and resilient modulus of compacted fine-grained subgrade soils

2017 ◽  
Vol 54 (5) ◽  
pp. 646-663 ◽  
Author(s):  
Zhong Han ◽  
Sai K. Vanapalli ◽  
Wei-lie Zou
Keyword(s):  
Moisture Content ◽  
Soil Water ◽  
Resilient Modulus ◽  
Characteristic Curve ◽  
Experimental Studies ◽  
Pavement Design ◽  
Soil Water Characteristic Curve ◽  
Subgrade Soils ◽  
Fine Grained ◽  
Integrated Approaches

This paper combines a series of approaches for predicting the soil-water characteristic curve (SWCC) and the variation of the resilient modulus (MR) of compacted fine-grained subgrade soils with moisture content, which is the key information required in mechanistic pavement design methods. The presented approaches for the SWCC and MR are integrated, as (i) they are developed following the same philosophy, (ii) they require only the measurements of the suction and moisture content or MR at saturated and optimum moisture content conditions for prediction, and (iii) the predicted SWCC is used for predicting the MR – moisture content relationship. Experimental studies have been performed on five fine-grained subgrade soils that were collected from different regions in Ontario, Canada, to determine their MR at various external stress levels and post-compaction moisture contents, as well as their SWCCs after the MR tests. Experimental measurements are predicted using the integrated approaches and the empirical approaches currently used in the mechanistic–empirical pavement design guide (MEPDG). It is demonstrated that the integrated approaches are easy to use and show improved reliability in predicting both the SWCC and MR for the investigated subgrade soils in spite of using limited experimental data.

A simplified method to estimate the soil-water characteristic curve

2010 ◽  
Vol 47 (12) ◽  
pp. 1382-1400 ◽  
Author(s):  
Kheng-Boon Chin ◽  
Eng-Choon Leong ◽  
Harianto Rahardjo
Keyword(s):  
Sensitivity Analysis ◽  
Soil Water ◽  
Characteristic Curve ◽  
Estimation Methods ◽  
Index Properties ◽  
Soil Water Characteristic Curve ◽  
Fine Grained ◽  
Simplified Method ◽  
Basic Index ◽  
The One

This paper proposes a simplified method to estimate the soil-water characteristic curve (SWCC) for both coarse- and fine-grained soils using one-point SWCC measurement and basic index properties. Parameters of the Fredlund and Xing SWCC equation were correlated with the basic properties of 60 soils: 30 soils each of coarse- and fine-grained types. Sensitivity analysis revealed that the location of the one-point measurement at matric suctions of 10 and 500 kPa gave the most reliable SWCC using the proposed method for coarse- and fine-grained soils, respectively. The validity of the proposed method was evaluated using a total of 62 soils collated from published literature with 31 soils each of the coarse- and fine-grained types. The proposed method gives a good estimation of the SWCC and uses fewer parameters when compared with existing one-point SWCC estimation methods.

scholarly journals A New Soil-Water Characteristic Curve Model for Unsaturated Loess Based on Wetting-Induced Pore Deformation

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Yuwei Zhang ◽  
Zhanping Song ◽  
Xiaolin Weng ◽  
Yongli Xie
Keyword(s):  
Soil Water ◽  
Characteristic Curve ◽  
Shift Factor ◽  
Model Parameters ◽  
Average Pore ◽  
Average Pore Radius ◽  
New Model ◽  
Soil Water Characteristic Curve ◽  
Unsaturated Loess ◽  
The Relationship

The soil-water characteristic curve (SWCC) is the basis for describing seepage, strength, and constitutive model of unsaturated soil. The existing SWCC models do not work accurately for evaluating loess, because they do not consider the pore deformation that is induced by wetting. The present study develops a new SWCC model for unsaturated loess. The model considers the effect of wetting-induced pore deformation (WIPD) on the SWCC. The new model includes 6 parameters, which could be confirmed by laboratory tests. The pore volume function (PVF) was described by the WIPD. The shift factor ξ1i and the compression factor ξ2i were introduced into the model. The relationship between the void ratio e and ξ1i and ξ2i was established using the average pore radius. The new SWCC model for saturated loess was improved based on the classical van Genuchten (V-G) model. If the WIPD had not been considered, the new model would regress into the classical V-G model. SWCC tests of unsaturated loess with different void ratios were carried out to verify the new model. The model parameters were calibrated in the original state, and the SWCCs of different void ratios were predicted by the new model and found to be in good agreement with the test results.

Study on Unsaturated Mechanism of Loess Compaction

2011 ◽  
Vol 368-373 ◽  
pp. 2960-2965
Author(s):  
Qing Feng Lv ◽  
Jing Wen Zhao ◽  
Sheng Xin Wang ◽  
Yan Xu Zhao
Keyword(s):  
Moisture Content ◽  
Soil Water ◽  
Unsaturated Soils ◽  
Pore Space ◽  
Characteristic Curve ◽  
Dry Density ◽  
Physical Factors ◽  
Mineral Component ◽  
Space Topology ◽  
Soil Water Characteristic Curve

The soil-water characteristic curve is an important constitutive feature of unsaturated soils, defining the relationship between the soil suction and moisture content. Mineral component and pore space topology are the most important physical factors affecting the soil-water characteristic, and that dry density synthetically reflects the mineral component and pore space topology. Compaction is a classical application involving unsaturated soil, and dry density represents the pore structure at special moisture content. Soil water characteristic curve for compacted loess is studied by test, and the effect of dry density on soil water characteristic curve is discussed. Based the soil-water characteristic curve and compaction curve, mechanism of compaction is explained. Research results show that the soil-water characteristic curves for all dry density soil intersect at the point, which is optimize moisture content, and suction is the most important factor affecting the compaction.

scholarly journals Irrigation Scheduling Based on Wireless Sensors Output and Soil-Water Characteristic Curve in Two Soils

Sensors ◽  
2020 ◽  
Vol 20 (5) ◽  
pp. 1336 ◽  
Author(s):  
J.D. Jabro ◽  
W.B. Stevens ◽  
W.M. Iversen ◽  
B.L. Allen ◽  
U.M. Sainju
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Soil Water ◽  
Root Zone ◽  
Sandy Loam ◽  
Characteristic Curve ◽  
Field Capacity ◽  
Irrigation Scheduling ◽  
Clay Loam ◽  
Soil Water Characteristic Curve

Data-driven irrigation planning can optimize crop yield and reduce adverse impacts on surface and ground water quality. We evaluated an irrigation scheduling strategy based on soil matric potentials recorded by wireless Watermark (WM) sensors installed in sandy loam and clay loam soils and soil-water characteristic curve data. Five wireless WM nodes (IRROmesh) were installed at each location, where each node consisted of three WM sensors that were installed at 15, 30, and 60 cm depths in the crop rows. Soil moisture contents, at field capacity and permanent wilting points, were determined from soil-water characteristic curves and were approximately 23% and 11% for a sandy loam, and 35% and 17% for a clay loam, respectively. The field capacity level which occurs shortly after an irrigation event was considered the upper point of soil moisture content, and the lower point was the maximum soil water depletion level at 50% of plant available water capacity in the root zone, depending on crop type, root depth, growth stage and soil type. The lower thresholds of soil moisture content to trigger an irrigation event were 17% and 26% in the sandy loam and clay loam soils, respectively. The corresponding soil water potential readings from the WM sensors to initiate irrigation events were approximately 60 kPa and 105 kPa for sandy loam, and clay loam soils, respectively. Watermark sensors can be successfully used for irrigation scheduling by simply setting two levels of moisture content using soil-water characteristic curve data. Further, the wireless system can help farmers and irrigators monitor real-time moisture content in the soil root zone of their crops and determine irrigation scheduling remotely without time consuming, manual data logging and frequent visits to the field.

SOIL WATER CHARCTERISTIC CURVES OF BENTONITES IN ISOCHORIC CONDITIONS DURING WETTING: MEASUREMENT AND PREDICTION

2020 ◽  
Author(s):  
Tadikonda Venkata Bharat ◽  
Yagom Gapak
Keyword(s):  
Soil Water ◽  
Unsaturated Flow ◽  
Characteristic Curve ◽  
Dry Density ◽  
Model Parameters ◽  
Empirical Relationships ◽  
Flow Simulations ◽  
Proposed Model ◽  
Theoretical Procedure

Determination of soil water characteristic curve (SWCC) of compacted bentonites in the isochoric condition is a prerequisite for unsaturated flow simulations in several geoenvironmental applications. The SWCC data are, however, not readily available for many compacted bentonites over a wide suction range due to difficulties associated with the testing. In this work, wetting SWCCs of four Indian bentonites of different plasticity were established experimentally at compaction dry densities of 1.4, 1.6, and 1.8 Mg/m3 in isochoric conditions using two independent laboratory techniques in different suction ranges. The modified Kovács (MK) model was extended to simulate the SWCC data of the Indian bentonites. Empirical relationships between MK model parameters and compaction dry density for these bentonites were obtained. A theoretical procedure for the estimation of SWCCs of the compacted bentonites based on the basic bentonite properties and proposed correlations was validated on the available wetting SWCC data of compacted GMZ, MX80, and FEBEX bentonites from the literature studies. The proposed model is useful for predicting the the SWCCs of bentonites from basic clay properties in the absence of measured data and in understanding the influence of dry density and plasticity on SWCC.

A Model for the Soil-Water Characteristic Curve and its Application in Dam Engineering

2011 ◽  
Vol 94-96 ◽  
pp. 1930-1935
Author(s):  
Zhen Hua Shi ◽  
Zhao Wan Gao
Keyword(s):  
Soil Water ◽  
Characteristic Curve ◽  
Earth Dam ◽  
Additional Parameter ◽  
Soil Water Characteristic Curve ◽  
Surface Plasticity ◽  
Hydraulic Behaviour ◽  
Proposed Model ◽  
Scanning Curves ◽  
Unsaturated Seepage

A mathematical model for the soil-water characteristic curve is proposed in the light of bounding surface plasticity. The main drying and wetting curves are taken as the asymptotes of the scanning curves, and only one additional parameter is introduced to simulate such scanning curves. To pave to the way for the application of the proposed model, the governing equation of unsaturated seepage problems and the finite element formulations are derived. A FEM program incorporating the SWCC model is then developed and used to study the hydraulic behaviour of an earth dam undergoes a repeated change of reservoir level. Numerical results confirm the possibility and necessity of using such a hysteresis model in unsaturated seepage problems.

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