TY - JOUR

T1 - Studying the soil pore physical resistance and resilience of a shallow volcanic ash soil subjected to pure cyclic loading

AU - Dörner, Jose

AU - Horn, Rainer

AU - Uteau, Daniel

AU - Rostek, Jens

AU - Zuniga, Felipe

AU - Peth, Stephan

AU - Dec, Dorota

AU - Fleige, Heiner

N1 - Funding Information: We thank the Fondecyt Grant 1130546 for funding the research project. We are also grateful for the fieldwork conducted by researchers and students of the Ñadi Soils Team and the hospitality of the landowners (Don Alfredo and Sra Elba). Dr. José Dörner thanks the Alexander von Humboldt Foundation for the Grant “Georg Foster Fellowship for Experienced Researchers”, which allowed a research visit to the Christian Albrechts University in Kiel, Germany during 2016 as well as for a renewed research stay in the framework of an Alumni Sponsorship 2019 at the Christian Albrechts University in Kiel and the University of Kassel (Germany).

PY - 2020/10

Y1 - 2020/10

N2 - In the last 250 years the Aquands (depth-limited and waterlogged-volcanic ash soils) in southern Chile were exposed to an intensive land use change inducing physical degradation of these fragile soils. The aim of this work was to evaluate the effect of cyclic loading on soil structural properties and the resilience capacity after simulating one event of soil waterlogging as usually occurs in the field. In undisturbed soil samples, collected from two horizons (2−5 cm, Hz1 [A 1] and 20−23 cm, Hz2 [B s1]) of a Duric Histic Placaquand under secondary native forest (sNF) and naturalized grassland (NG), the precompression stress (Pc), deformation and recovery indices derived from cyclic loading tests (20, 80 and 200 kPa) were determined. The air permeability (Ka) and soil volume changes were measured during the entire test. The land use change from sNF to NG increased the rigidity of the pore system due to plastic deformation. However, the cyclic loading provokes changes in the pore system (e.g. increase in bulk density as well as decrease in wide coarse pores, which finally induce a decrease in air permeability: 1.89 to -0.17 log μm 2 and 1.03 to 0.37 log μm 2 in Hz1 of aNF and NG, respectively) even at loads lower than Pc highlighting the fragility of the soils. As the applied load increases to levels higher than Pc, the plastic deformation induces an increase in pore water pressure and mechanical strength, affecting the pore network and in turn the air permeability of the soil. After one event of ten days of waterlogging conditions, the resilience capacity of the pore system was low. CT-images show that the soil under sNF recovered apart of the deformed porosity allowing an increase in Ka (0.55 ± 0.15 log μm 2) after waterlogging conditions, however, no changes were identified for the soil under NG (final Ka = 0.57 ± 0.26 log μm 2). Therefore, both land use change and increasing loads on these fragile soils imply the loss of their resilience capacity generating a further soil settlement.

AB - In the last 250 years the Aquands (depth-limited and waterlogged-volcanic ash soils) in southern Chile were exposed to an intensive land use change inducing physical degradation of these fragile soils. The aim of this work was to evaluate the effect of cyclic loading on soil structural properties and the resilience capacity after simulating one event of soil waterlogging as usually occurs in the field. In undisturbed soil samples, collected from two horizons (2−5 cm, Hz1 [A 1] and 20−23 cm, Hz2 [B s1]) of a Duric Histic Placaquand under secondary native forest (sNF) and naturalized grassland (NG), the precompression stress (Pc), deformation and recovery indices derived from cyclic loading tests (20, 80 and 200 kPa) were determined. The air permeability (Ka) and soil volume changes were measured during the entire test. The land use change from sNF to NG increased the rigidity of the pore system due to plastic deformation. However, the cyclic loading provokes changes in the pore system (e.g. increase in bulk density as well as decrease in wide coarse pores, which finally induce a decrease in air permeability: 1.89 to -0.17 log μm 2 and 1.03 to 0.37 log μm 2 in Hz1 of aNF and NG, respectively) even at loads lower than Pc highlighting the fragility of the soils. As the applied load increases to levels higher than Pc, the plastic deformation induces an increase in pore water pressure and mechanical strength, affecting the pore network and in turn the air permeability of the soil. After one event of ten days of waterlogging conditions, the resilience capacity of the pore system was low. CT-images show that the soil under sNF recovered apart of the deformed porosity allowing an increase in Ka (0.55 ± 0.15 log μm 2) after waterlogging conditions, however, no changes were identified for the soil under NG (final Ka = 0.57 ± 0.26 log μm 2). Therefore, both land use change and increasing loads on these fragile soils imply the loss of their resilience capacity generating a further soil settlement.

KW - Soil mechanical properties

KW - Soil structure recovery

KW - Pore functions

KW - Andisols

KW - CT-Analysis

UR - http://www.scopus.com/inward/record.url?scp=85086585139&partnerID=8YFLogxK

U2 - 10.1016/j.still.2020.104709

DO - 10.1016/j.still.2020.104709

M3 - Article

VL - 204

JO - Soil & tillage research

JF - Soil & tillage research

SN - 0167-1987

M1 - 104709

ER -