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.

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.

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.

Model for the prediction of shear strength with respect to soil suction

1996 ◽  
Vol 33 (3) ◽  
pp. 379-392 ◽  
Author(s):  
S K Vanapalli ◽  
D G Fredlund ◽  
D E Pufahl ◽  
A W Clifton
Keyword(s):  
Shear Strength ◽  
Soil Water ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Characteristic Curve ◽  
Experimental Studies ◽  
Matric Suction ◽  
Glacial Till ◽  
Soil Suction ◽  
Soil Water Characteristic Curve

Experimental studies on unsaturated soils are generally costly, time-consuming, and difficult to conduct. Shear strength data from the research literature suggests that there is a nonlinear increase in strength as the soil desaturates as a result of an increase in matric suction. Since the shear strength of an unsaturated soil is strongly related to the amount of water in the voids of the soil, and therefore to matric suction, it is postulated that the shear strength of an unsaturated soil should also bear a relationship to the soil-water characteristic curve. This paper describes the relationship between the soil-water characteristic curve and the shear strength of an unsaturated soil with respect to matric suction. Am empirical, analytical model is developed to predict the shear strength in terms of soil suction. The formulation makes use of the soil-water characteristic curve and the saturated shear strength parameters. The results of the model developed for predicting the shear strength are compared with experimental results for a glacial till. The shear strength of statically compacted glacial till specimens was measured using a modified direct shear apparatus. Specimens were prepared at three different water contents and densities (i.e., corresponding to dry of optimum, and wet of optimum conditions). Various net normal stresses and matric suctions were applied to the specimens. There is a good correlation between the predicted and measured values of shear strength for the unsaturated soil. Key words: soil-water characteristic curve, shear strength, unsaturated soil, soil suction, matric suction.

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.

Measurement of soil-water characteristic curves for fine-grained soils using a small-scale centrifuge

2002 ◽  
Vol 39 (5) ◽  
pp. 1209-1217 ◽  
Author(s):  
R M Khanzode ◽  
S K Vanapalli ◽  
D G Fredlund
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Characteristic Curve ◽  
Small Scale ◽  
Characteristic Curves ◽  
Pressure Plate ◽  
Soil Water Characteristic Curve ◽  
Fine Grained ◽  
Soil Water Characteristic Curves ◽  
Plate Apparatus

Considerably long periods of time are required to measure soil-water characteristic curves using conventional equipment such as pressure plate apparatus or a Tempe cell. A commercially available, small-scale medical centrifuge with a swinging type rotor assembly was used to measure the soil-water characteristic curves on statically compacted, fine-grained soil specimens. A specimen holder was specially designed to obtain multiple sets of water content versus suction data for measuring the soil-water characteristic curve at a single speed of rotation of the centrifuge. The soil-water characteristic curves were measured for three different types of fine-grained soils. The three soils used in the study were processed silt (liquid limit, wL = 24%; plasticity index, Ip = 0; and clay = 7%), Indian Head till (wL = 35.5%, Ip = 17%, and clay = 30%), and Regina clay (wL = 75.5%, Ip = 21%, and clay = 70%). The soil-water characteristic curves for the above soils were measured in 0.5, 1, and 2 days, respectively, using the centrifuge technique for suction ranges from 0 to 600 kPa. Time periods of 2, 4–6, and 16 weeks were required for measuring the soil-water characteristic curves for the same soils using a conventional pressure plate apparatus. There is reasonably good agreement between the experimental results obtained by the centrifuge and the pressure plate methods. The results of this study are encouraging as soil-water characteristic curves can be measured in a reduced time period when using a small-scale centrifuge.Key words: unsaturated soils, soil-water characteristic curve, centrifuge technique, soil suction, matric suction, water content.

Experimental Study on Gravel Soils of Matrix Suction

2013 ◽  
Vol 275-277 ◽  
pp. 310-315 ◽  
Author(s):  
Hong Mei Tang ◽  
Pei Wei Liao ◽  
Lin Feng Wang ◽  
Hong Kai Chen
Keyword(s):  
Moisture Content ◽  
Water Content ◽  
Soil Water ◽  
Characteristic Curve ◽  
Curved Surface ◽  
Soil Water Characteristic Curve ◽  
Content Change ◽  
Two Factors ◽  
The Matrix ◽  
Matrix Suction

Soil-water characteristic curve（SWCC）is closely relevant to two main factors which are structure and moisture content. According to the two factors the values of matrix suction of 45 groups experimental specimens within different moisture content and soil -stone ratio of unsaturated soil are get through filter paper method. Date analysis shows that relation between matrix suction and soil-stone ratio at different moisture states is of different characteristics. Relation between matrix suction and water content is notably nonlinear. Distribution of matrix suction is curved surface in the moisture and soil-stone ration state space which is the function of water content and soil-stone ratio, in which the axial plan is parallel to the axis of soil-stone ratio.At low water content,the matrix suction on the moisture content change is very sensitive, at high moisture content and closed to saturation stage matrix suction hardly changes along with water content and soil-stone ratio change. The curved surface which Located in the middle section ,the matrix suction on the change of water content are more sensitive, reduced with water content increasing; and in this phase the matrix suction is insensitive to the variation of soil-stone ratio. Finally, it is concluded that the saturation to describe the soil water characteristic curve is a bad choice, with moisture to depict the so. In contrast, directly using the water content to describe the soil water characteristic curve is better.

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