Wetting front advancing column test for measuring unsaturated hydraulic conductivity

2009 ◽  
Vol 46 (12) ◽  
pp. 1431-1445 ◽  
Author(s):  
X. Li ◽  
L. M. Zhang ◽  
D. G. Fredlund
Keyword(s):  
Hydraulic Conductivity ◽  
Large Scale ◽  
Soil Column ◽  
Measurement Range ◽  
Wetting Front ◽  
Time Saving ◽  
Steady State Method ◽  
Unsaturated Hydraulic Conductivity ◽  
Soil Wetting ◽  
Wetting Process

Unsaturated hydraulic conductivity is the primary soil parameter required when performing seepage analyses for unsaturated–saturated soil systems. Unsaturated hydraulic conductivity is also one of the most difficult parameters to measure because of the time involved and the limited suction measurement range (e.g., 0∼1500 kPa in a test using the steady-state method). In this study, a new wetting front advancing method was developed for measuring unsaturated hydraulic conductivity. The wetting front advancing method simulates and monitors a soil wetting process through a large-scale soil column. A new interpretative procedure was developed to calculate the unsaturated hydraulic conductivity based on the monitored water content, suction, and wetting front advancing velocity. The proposed technique is used to measure the unsaturated hydraulic conductivities of five soils, which vary from gravel to clay. The results indicate that the proposed technique is time-saving (i.e., requires several days for a complete test) and is applicable over wide ranges of suctions and unsaturated hydraulic conductivities. The measured unsaturated hydraulic conductivity using the wetting front advancing method is similar to that obtained using the instantaneous profile method, with the latter covering narrower ranges of soil suction and hydraulic conductivity.

Simulating transient infiltration in unsaturated soils

1998 ◽  
Vol 35 (6) ◽  
pp. 1093-1100 ◽  
Author(s):  
J R McDougall ◽  
I C Pyrah
Keyword(s):  
Hydraulic Conductivity ◽  
Unsaturated Soils ◽  
Flow Model ◽  
Unsaturated Flow ◽  
Surface Region ◽  
Infiltration Rate ◽  
Soil Suction ◽  
Wetting Front ◽  
Near Surface ◽  
Unsaturated Hydraulic Conductivity

Transient responses to various infiltration events have been examined using an unsaturated flow model. Numerical simulations reveal a range of infiltration patterns which can be related to the ratio of infiltration rate to unsaturated hydraulic conductivity. A high value of this ratio reflects a prevailing hydraulic conductivity which cannot readily redistribute the newly infiltrated moisture. Moisture accumulates in the near-surface region before advancing down through the soil as a distinct wetting front. In contrast, low values of the ratio of rainfall to unsaturated hydraulic conductivity show minimal moisture accumulation, as the relatively small volumes of infiltrating moisture are readily redistributed through the soil profile.Key words: numerical modelling, infiltration, unsaturated soil, soil suction, groundwater.

Surface-positioned double-ring to improve traditional infiltrometer for measuring soil infiltration

Soil Research ◽  
2020 ◽  
Vol 58 (3) ◽  
pp. 314
Author(s):  
Jing Zhang ◽  
Shaopeng Li
Keyword(s):  
Hydraulic Conductivity ◽  
Measurement Accuracy ◽  
Soil Column ◽  
Saturated Hydraulic Conductivity ◽  
Experimental Results ◽  
Water Infiltration ◽  
Maximum Relative Error ◽  
Wetting Front ◽  
Double Ring ◽  
Improve Measurement

The installation of a traditional double-ring infiltrometer (DRI) into soil is difficult and time consuming. It results in reduced accuracy because of soil disturbance and water leakage along the gaps between the ring wall and the soil. In this study, a surface-positioned DRI (SPDRI) was suggested to improve measurement accuracy and convenience of the DRI. Laboratory experiments were conducted to evaluate performance of the method in terms of the influence of the lateral flow of water on the accuracy of infiltration rate, average vertical wetting front depth and saturated hydraulic conductivity. A cylindrical soil column was used to simulate the ideal ring infiltrometer (IRI) of the one-dimensional vertical infiltration process for comparison purposes. Experimental results indicated that the infiltration rates measured by the SPDRI and IRI were nearly identical, with maximum relative error (RE) of 18.75%. The vertical wetting front depth of the SPDRI was nearly identical to that of the IRI, with proportional coefficients of 0.97 and R2 > 0.95. Comparison of the soil saturated hydraulic conductivity with those from IRI indicated that the REs were 7.05–10.63% for the SPDRI. Experimental results demonstrated that the SPDRI could improve the measurement accuracy and facilitate the soil water infiltration measurement process.

scholarly journals Determining the Unsaturated Hydraulic Conductivity of Remoulded Loess with Filter Paper Method and Soil Column Seepage Test

2021 ◽  
Author(s):  
Wenwu Chen ◽  
Quanquan Jia ◽  
Peng Liu ◽  
Yanmei Tong
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Filter Paper ◽  
Characteristic Curve ◽  
Soil Column ◽  
Volumetric Water Content ◽  
Experimental Results ◽  
Paper Test ◽  
Unsaturated Hydraulic Conductivity ◽  
The One

Abstract Loess is very widely distributed, and the unsaturated hydraulic conductivity of loess is related to many engineering issues. In order to determine the unsaturated hydraulic conductivity of remolded loess more conveniently and at a lower cost, filter paper test and soil column seepage test were carried out. The results indicate that in the one-dimensional soil column seepage process, the unsaturated hydraulic conductivity of loess increases with the increase of the volumetric water content, and as the seepage time continues, the unsaturated hydraulic conductivity of loess at different depths gradually becomes uniform. The changes in the microstructure indicate that the collapsible settlement will occur during the seepage process, which will reduce the unsaturated hydraulic conductivity of the underlying loess to a certain extent. Compared with the experimental results, the soil hydraulic conductivity curve (SHCC) obtained by the van Genuchten-Mualem model (VG-M model) underestimates the magnitude of unsaturated hydraulic conductivity in the part with a low volumetric water content (< 20%). and the Childs ༆ Collis-George model (CCG model) has more consistent results with the experimental results because it is based on more segments of the soil-water characteristic curve (SWCC).

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