Application of mid-infrared spectroscopy for rapid characterization of key soil properties for engineering land use

AbstractMethods for rapid and accurate soil tests are needed for the index properties of material attributes commonly applied in civil engineering. We tested the application of mid-infrared (MIR) spectroscopy for the rapid characterization of selected key stability-related soil properties. Two sample sets, representing different soils from across Lake Victoria basin in Kenya, were used for the study: A model calibration set (n=135) was obtained following a conditioned Latin hypercube sampling, and a validation set (n=120) was obtained from independent sites using a spatially stratified random sampling strategy. Air-dried ground (<0.5mm) soil was scanned using a high-throughput screening accessory for diffuse reflectance attached to a Fourier transform infrared spectrometer. The soil properties were calibrated to smoothed first derivative MIR spectra using partial least-square regression (PLS), and screening tests were developed for various limitation classes applicable in civil works using the soft independent modeling of class analogy (SIMCA). The hold-out full cross-validation coefficient of determination (r2)≥0.8 was obtained for the liquid limit (LL), linear shrinkage (LS), coefficient of linear extensibility (COLE), air-dried moisture content, (W) and cation exchange capacity (CEC). Further independent validation gave r2≥0.73 and the ratio of prediction deviation (RPD) 4.4–2.1 for LL, LS, COLE, W, CEC, plastic limit (PL), plasticity index (PI), and volumetric shrinkage (VS). The independent validation likelihood ratios for the diagnostic screening tests were: LL>55%, 4.2; PI>30%, 2.7; LS>12%, 2.4; exchangeable sodium (eNa)>2cmol (+) kg−1, 2.3; exchangeable sodium percent (ESP)>10%, 1.8; W>8.3%, 1.6, and Activity number (A)>1.25units, 1.5. MIR can provide the rapid assessment of several soil properties that yield stability indices in material testing for engineering land use. Further studies should test the ability of MIR PLS for establishing broader calibrations across more diverse soil types and the direct correlation of MIR to material functional attributes

The efficacy of lignosulfonate in controlling the swell potential of expansive soil and its stabilization mechanisms

Many techniques have been developed and applied to prevent and/or remediate infrastructural damage caused by expansive soils throughout the world. Of these techniques, traditional chemical (lime and cement) stabilization has gained world attention because of a good understanding of the underlying mechanisms, availability of technical guidelines, and years of demonstrated field experiences. However, despite the global acceptance of traditional additives for treating expansive soil, other environmentally benign alternatives have been an important subject of research due to the inherent health and safety concerns for traditional admixtures. One such alternative is from the paper industry that manufactures pulp from wood and in the process produces over 50 million tons annually of a waste substance known as lignosulfonate (LS). This substance has been disposed of as a waste product resulting in colossal disposal cost; however, it does have a potential application in geotechnical engineering under the concept of sustainable development. This investigation into LS admixture consists of experimental and theoretical studies. The experimental investigation involved a laboratory evaluation of the efficacy of LS admixture in controlling the swell potential of a remoulded expansive soil. The swell potential was examined in terms of percent swell and swell pressure of the soil. In addition to these engineering properties, the Atterberg limits, unconfined compressive strength, durability (wet/dry and freeze/thaw), compaction characteristics, permeability, consolidation characteristics, and shrinkage behaviours were also investigated. Furthermore, the mechanism by which the remoulded soil was modified or altered by the LS admixture was probed and identified. The optimum content of LS admixture was found to be about 2% by dry weight of the soil. Standard geotechnical laboratory tests performed on untreated and treated compacted soil specimens showed significant and consistent changes in the swell potential and other engineering properties such that the percent swell decreased by 22% while maintaining the soil’s pH. In some instances, identical specimens treated with 2% cement were prepared and tested for comparison. Although the specimens treated with cement recorded a 33% reduction in the percent swell, the ductile characteristics were replaced by brittleness and a significant increase in pH. Further analysis of the laboratory test data also suggested that LS admixture is a resourceful alternative for “low” swelling soils. This finding led to the formation of a “LS application chart” that will help geotechnical practitioners on admixture choice for a particular expansive soil deposits. The physical-chemical analyses of untreated and 2% LS treated specimens were studied microstructurally after 7 days of curing. When LS was added into expansive soil, the stabilization mechanisms consisted of an insignificant exchange of interlayer cations due to the “cover-up-effect”, basal/peripheral adsorption on mineral surfaces through hydrogen bonding (water bridging), direct bonding to dehydrated cations with the subsequent formation of flocculation-aggregates, initial expansion of diffuse double layer and water entrapment, and a waterproofing effect. An elemental analysis of untreated and treated specimens suggested inter-molecular interactions between soil minerals and the LS admixture as opposed to major chemical reactions. Thus, LS summarily altered the crystallographic characteristics of the soil minerals, and helped to reduce shrink-swell behaviour of the otherwise expansive soil. The theoretical aspect of this research work involved the development of a robust mathematical model to predict the swell behaviour of expansive soil treated with LS. Relationships were proposed to estimate the suction behaviour of treated soil using laboratory data obtained experimentally. Suction behaviour was governed by a single constant (β), which depends on an input variable; the degree of saturation (Sd). A reasonable correlation was found between the percent swell determined experimentally and the predicted values. A non-traditional admixture such as LS has the potential to become a technically and economically competitive alternative in the stabilization of expansive soils. With over 50 million tons being produced annually, the successful use of LS admixture as a new stabilization material for expansive soil appears to be one of many viable solutions to the sustainable use of a waste by-product, green construction, and as well as saving the disposal problems inherent in the paper manufacturing industry

Kaolin Clay Reinforced with a Granular Column Containing Crushed Waste Glass or Traditional Construction Sands

Installation of granular columns is a cost-effective and versatile in situ technique to improve the shear strength, settlement, and drainage behavior of weak soils. It involves backfilling vertical boreholes in the ground with granular materials stiffer than the native soil, such as stone or compacted sand. However, the massive use and overexploitation of sand and natural aggregates have depleted their reserves in recent decades, causing damage to the environment, creating sand shortages, and skyrocketing their price. Hence, it is essential to develop a sustainable alternative to natural aggregates to construct granular columns. The ever-increasing stockpiles of waste glass could be a potential replacement for natural sand in several geotechnical construction applications, noting that both materials have a similar chemical composition. Using crushed waste glass (CWG) as an alternative to traditional natural and manufactured (quarried) sands in granular columns could offer a multipronged benefit by recycling nonbiodegradable waste (glass) and by conserving a depleting natural resource (sand). Using a large direct shear (LDS) machine, this study investigated the shear strength behavior of kaolin (to represent a typical weak soil) reinforced with a central granular column. Three different materials were separately used to backfill the column, including natural sand (NS), manufactured sand (MS), and CWG. The results revealed that the geocomposites containing the CWG column have the highest peak friction angle and relatively greater shear strength under high normal stresses, favoring the potential use of CWG as a green alternative to traditional sands in backfilling granular columns, ultimately supporting resource conservation, waste recycling, and the paradigm shift toward a circular economy

Kaolin clay reinforced with a granular column containing crushed waste glass or traditional construction sands

Installation of granular columns is a cost-effective and versatile in situ technique to improve the shear strength, settlement, and drainage behaviour of weak soils. It involves backfilling vertical boreholes in the ground with granular materials stiffer than the native soil, such as stone or compacted sand. However, the massive use and overexploitation of sand and natural aggregates have depleted their reserves in recent decades, causing damage to the environment, creating sand shortages and skyrocketing their price. Hence, it is essential to develop a sustainable alternative to natural aggregates to construct granular columns. The ever-increasing stockpiles of waste glass could be a potential replacement for natural sand in several geotechnical construction applications, noting that both materials have a similar chemical composition. Using crushed waste glass (CWG) as an alternative to traditional natural and manufactured (quarried) sands in granular columns could offer a multi75 pronged benefit by recycling non-biodegradable waste (glass) and by conserving a depleting natural resource (sand). Using a large direct shear (LDS) machine, this study investigated the shear strength behaviour of kaolin (to represent a typical weak soil) reinforced with a central granular column. Three different materials were separately used to backfill the column, including natural sand (NS), manufactured sand (MS) and CWG. The results revealed that the geocomposites containing the CWG column have the highest peak friction angle and relatively greater shear strength under high normal stresses, favouring the potential use of CWG as a green alternative to traditional sands in backfilling granular columns, ultimately supporting resource conservation, waste recycling and the paradigm shift towards a circular economy

Long-term comparison between waste paper fly ash and traditional binder as hydraulic road binder exposed to sulfate concentrations

Sulfate attack is one of the drawbacks of cementitious materials for stabilized soils. In the current study, a durability comparison of stabilized soil with cement (Type IV) and waste paper fly ash (WPFA) was conducted. First, the treated soil’s unconfined compressive strength (UCS) was tested. Next, the treated soil was subjected to various wetting/drying cycles with various sulfate concentrations and temperatures for a year. In the meantime, samples were taken for DRX, FTIR, and TGA microstructural analyses. Additionally, samples were manufactured to track swelling over an 800 day period. The outcomes show that WPFA’s UCS remained constant. Furthermore, ettringite development can be seen in the microstructural studies, however testing on linear displacement over 800 days revealed no significant changes in swelling. Finally, SEM was used to verify the ettringite formation at 360 days in order to confirm the previous findings. All the results indicated that stabilizing soil with 5% of WPFA and 3% of cement IV is possible even in presence of high sulfate concentrations, while maintaining the durability of the structure.This research was funded by European Union’s Horizon 2020, grant number 730305.Peer ReviewedPostprint (published version

Development of a Multimode Instrument for Remote Measurements of Unsaturated Soil Properties

The hydromechanical behavior of soil is governed by parameters that include the moisture content, soil matric potential, texture, and the mineralogical composition of the soil. Remote characterization of these and other key properties of the soil offers advantages over conventional in situ or laboratory-based measurements: information may be acquired rapidly over large, or inaccessible areas; samples do not need to be collected; and the measurements are non-destructive. A field-deployable, ground-based remote sensor, designated the Soil Observation Laser Absorption Spectrometer (SOLAS), was developed to infer parameters of bare soils and other natural surfaces over intermediate (100 m) and long (1,000 m) ranges. The SOLAS methodology combines hyperspectral remote sensing with differential absorption and laser ranging measurements. A transmitter propagates coherent, near-infrared light at on-line (823.20 nm) and off-line (847.00 nm) wavelengths. Backscattered light is received through a 203-mm diameter telescope aperture and is divided into two channels to enable simultaneous measurements of spectral reflectance, differential absorption, and range to the target. The spectral reflectance is measured on 2151 continuous bands that range from visible (380 nm) to shortwave infrared (2500 nm) wavelengths. A pair of photodetectors receive the laser backscatter in the 820–850 nm range. Atmospheric water vapor is inferred using a differential absorption technique in conjunction with an avalanche photodetector, while range to the target is based on a frequency-modulated, self-chirped, homodyne detection scheme. The design, fabrication, and testing of the SOLAS is described herein. The receiver was optimized for the desired backscatter measurements and assessed through a series of trials that were conducted in both indoor and outdoor settings. Spectral reflectance measurements collected at proximal range compared well with measurements collected at intermediate ranges, demonstrating the utility of the receiver. Additionally, the noise characteristics of the spectral measurements were determined across the full range of the detected wavelengths. Continued development of the SOLAS instrument will enable range-resolved and water vapor-corrected reflectance measurements over longer ranges. Anticipated applications for the SOLAS technology include rapid monitoring of earth construction projects, geohazard assessment, or ground-thruthing for current and future satellite-based multi- and hyperspectral data

Combining visible near-infrared spectroscopy and water vapor sorption for soil specific surface area estimation

Abstract The soil specific surface area (SSA) is a fundamental property governing a range of soil processes relevant to engineering, environmental, and agricultural applications. A method for SSA determination based on a combination of visible near‐infrared spectroscopy (vis‐NIRS) and vapor sorption isotherm measurements was proposed. Two models for water vapor sorption isotherms (WSIs) were used: the Tuller–Or (TO) and the Guggenheim–Anderson–de Boer (GAB) model. They were parameterized with sorption isotherm measurements and applied for SSA estimation for a wide range of soils (N = 270) from 27 countries. The generated vis‐NIRS models were compared with models where the SSA was determined with the ethylene glycol monoethyl ether (EGME) method. Different regression techniques were tested and included partial least squares (PLS), support vector machines (SVM), and artificial neural networks (ANN). The effect of dataset subdivision based on EGME values on model performance was also tested. Successful calibration models for SSATO and SSAGAB were generated and were nearly identical to that of SSAEGME. The performance of models was dependent on the range and variation in SSA values. However, the comparison using selected validation samples indicated no significant differences in the estimated SSATO, SSAGAB, and SSAEGME, with an average standardized RMSE (SRMSE = RMSE/range) of 0.07, 0.06 and 0.07, respectively. Small differences among the regression techniques were found, yet SVM performed best. The results of this study indicate that the combination of vis‐NIRS with the WSI as a reference technique for vis‐NIRS models provides SSA estimations akin to the EGME method