Shrinkage Characteristics Of Soil Research Articles

High salinity prolongs water processes required for soil structure stability during drying–wetting cycles

AbstractClimate events, such as drought and rainfall, can lead to a cycle of drying and wetting that may cause changes in soil structure, leading to deteriorations in the health of saline soils. However, little is known about the extent and behavior of soil structure degradation under the combined influences of salinity and drying–wetting (D‐W) cycles. Thus, we systematically investigated the effects of salinity (0, 5, 30, and 100 g/L, labeled as CK, T5, T30, and T100) and D‐W cycles on soil structure by determining soil volume, shrinkage, and swelling potentials along with soil pore character obtained from soil shrinkage characteristics curve, intending to explore how D‐W cycles and salinity affect soil structure. The results showed that soil deformation behaviors in saline and non‐saline soils varied with the number of D‐W cycles. Irreversible deformation of the soil was observed during continual D‐W cycles. The soil volume increased by 3.75%–15.73% after three D‐W cycles. In vertical direction, the maximum expansion magnitude for each treatment was reached with the value of 29.03%, 23.42%, 34.23%, and 35.87% in CK, T5, T30, and T100, respectively. The magnitudes of shrinkage and expansion were equal in the horizontal direction since the soil samples consistently returned to their original dimensions. Furthermore, the decrease was observed in the micropores and capillary pores affected by salinity, with values of 50%, 58.6%, and 70.4% in CK, T5, T30, and T100, respectively. However, the D‐W cycles primarily affected large pores. High salinity levels enhanced swelling potential and inhabit shrinkage potential, prolonging the water processes required for the soil structure to achieve stability. The results of this study underscore the necessity of understanding the hysteresis of soil volume change and elucidate the mechanisms of soil structure deterioration driven by salinity and D‐W cycles. These findings provide a valuable reference for healthier soil management.

Frost Resistance and Shrinkage Characteristics of Soil Stabilized by Carbide Slag and Coal Gangue Powder

With the increase of expressway construction in seasonal frozen soil region, the freeze-thaw problem of subgrade soil has attracted more and more attention. In addition, the comprehensive utilization of industrial solid waste has become an important measure to build a resource-saving and environment-friendly society. In order to improve the frost resistance of subgrade soil and realize the resource utilization of industrial solid waste, carbide slag (CS) and coal gangue powder (CG) were applied to the subgrade soil. The unconfined compressive strength (UCS) test, freeze-thaw cycle test, dry shrinkage test, temperature shrinkage test and scanning electron microscope (SEM) test were carried out on CS-CG stabilized soil with a ratio of CS:CG = 70:30 and dosages of 5%, 10% and 15%. The freeze-thaw cycle degradation model of CS-CG stabilized soil was constructed to show the freeze-thaw deterioration mechanism after the mechanical properties, pore structure, and durability characteristics of the stabilized soil were examined. The results showed that the CS-CG stabilized soil had good frost resistance. After 6 freeze-thaw cycles, the UCS at 7d and 28 d was 2.86 MPa and 3.79 MPa, respectively, which were 22.6% and 35.5% lower than in samples that underwent no freeze-thaw action. The CS-CG stabilized soil had good crack resistance, slightly better dry shrinkage strain than lime stabilized soil, and excellent temperature shrinkage performance. With the increase of CS-CG dosage, the hydration products increased continuously. After freeze-thaw cycles, however, large pores and cracks gradually appeared in the stabilized soil, which led to an increase of porosity and pore diameter, and a decrease of pore abundance. Due to the influence of hydration degree, the porosity change at 7 d was less than that at 28 d. There was a f(n)/f0=βexp−λΔh relationship between UCS residual ratio and porosity variation of the CS-CG stabilized soil, and it had a good correlation. The CS-CG stabilized soil had good frost resistance and shrinkage characteristics, and could replace traditional cementitious materials such as Portland cement (PC) and lime for subgrade soil improvement in regions with seasonal frozen soil. Future research needs to focus on the performance regulation of CS-CG stabilized soil, which can make it more widely used.

Experimental investigations of soil shrinkage characteristics and their effects on the soil water characteristic curve

The magnitude of the volume change in response to changes in the water content is usually described by the soil-shrinkage characteristic curve (SSCC). The void ratio of soil is affected by its shrinkage behavior, and the soil water characteristic curve (SWCC) will be affected. In this paper, a new test platform is introduced to measure the soil shrinkage behavior during the drying process of silicon micropowder (SMP), Guangxi Guiping clay (GGC) and kaolin. The soil water characteristic curves of these tested soils were measured without and with considering volume change during soil shrinking. The results show that after drying ended, the volume shrinkage values of the soil samples were 0.31%, 20.1% and 31.4%, while the corresponding initial void ratios were 0.67, 1.03, and 1.04, respectively. The soil shrinkage curve with decreasing water content could be divided into three stages: normal shrinkage, residual shrinkage and zero shrinkage. In addition, the void ratio after soil shrinkage had a considerable influence on the SWCC. • This paper proposed a new method for measuring the shrinkage and deformation of soil samples. • The soil water characteristic curves are measured without and with considering volume change during soil shrinking. • The void ratio after soil shrinkage had a considerable influence on the SWCC.

Alkali activation of clayey soil using GGBS and NaOH

Construction of buildings and other engineering structures on the expansive soil is risky due to its high compressibility, low shear strength and unequal settlement. Expansive soils like clayey soil always create a problem in foundation. The problems involved during foundation are swelling, shrinkage characteristics of soil. An experimental study is carried out to improve the stability of the clayey soil using Ground Granulated Blast Furnace Slag (GGBS) and 12 M Sodium Hydroxide (NaOH). The Alkali to Binder ratio (A/B) maintained is 0.40 and 0.60. The amount of GGBS percentage added to the soil is 6%, 12%, 18% and 24%. The strength of the soil is tested at the 7th, 14th and the 28th day using the Unconfined Compressive Strength Test. The strength achieved at the 28th day for the Alkali to Binder ratio (A/B) of 0.60 for different percentages of GGBS is 580 KPa, 1880 KPa, 2803 KPa, 4062 KPa.

Effect of Natural Fibers Composites as Soil Stabilizer on Flexible Pavement Design

The primary function of road pavement is to distribute and transmit the wheel loads at the surface to a sufficiently large area of sub grade without failure or excessive deformation. The sub grade must be stable, unyielding, properly drained and free from volume changes due to the reasons such as structural, functional, or materials failure, or a combination of these. This project is being developed to be implemented in Perur – Ukkadam by-pass road of Coimbatore,Tamilnadu, India . It is around 2.2 Kms in length. In the study area, it is observed that the pavement failure is under the category of swelling and shrinkage characteristics of soil. To overcome this failure, its necessary to improve the bearing capacity of sub grade soil . For this purpose the Natural Fiber Composites (Coir & Sisal) were used in improving the soil bearing capacity and checked for CBR test to design flexible pavement. Thus this study shows the effectiveness of Natural Fiber Composites (Coir & Sisal) in improving performance characteristics of pavements.

An image-based method for quick measurement of the soil shrinkage characteristics curve of soil slurry

This paper presents a new method for determining the shrinkage curve. In this method, a 10 mm high, 80 mm diameter cylindrical dish with smooth interior is filled completely with soil slurry and placed on an electronic balance and then subjected to drying. Images of the soil surface are taken periodically from a fixed location, from which the surface area of the shrinking soil mass is determined by converting the images to binary images. The decreasing bulk volume of the soil is determined from the surface area and the varying thickness of the soil, which is determined from the known initial and measured final thickness (measured with calipers) and assuming that the change in specimen thickness is proportional to the change in its radius at any stage of drying. This method compares favorably with results of the balloon method using the same slurry sample material. Data from this method also fits very well to an existing shrinkage curve equation. This method is effortless, less time consuming than existing methods, and data acquisition can be automated. In addition, the shrinkage curve can be obtained in a relatively short period of 48 h as compared to existing methods that take days or even weeks. The limitation of measuring the shrinkage curve on soil slurry as presented in this work is that it does not represent the structural shrinkage zone.

Temporal dynamics of paddy soil structure as affected by different fertilization strategies investigated with soil shrinkage curve

The paddy soil presents strong structural dynamics due to tillage and frequent Wetting/Drying (WD) cycles. Fertilization practices can affect soil structure and therefore may alter their dynamics. The aim of this study was to investigate the temporal dynamics of paddy soil structure as affected by fertilization strategies using soil shrinkage characteristics. Four long-term fertilization treatments were selected: no fertilization as a control (CK), mineral fertilizer (NPK), mineral fertilizer plus green manure (GM), mineral fertilizer plus green manure and swine manure (GSM). Undisturbed soil cores and bulk soil samples were collected four times during WD cycles. Soil physical properties and shrinkage curves were measured. The results showed that soil bulk density and aggregate stability increased during drying and decreased during wetting, while soil shrinkage capacity was on the contrary. Relative to CK and inorganic fertilization, the application of organic manure decreased soil bulk density and increased aggregate stability, but had no impact on soil shrinkage capacity. Detailed shrinkage analyses manifested the different shrinkage patterns for the different treatments. The GSM treatment had more structural shrinkage than the CK, NPK, and GM treatments because more inter-aggregate pores developed in the GSM treatment. The shrinkage behavior of organic fertilizer treated soils (GSM and GM treatments) was more stable during WD cycles than the NPK and CK treatments. Besides, the CK and NPK treatments had greater slopes at the inflection point (slopeinflection), indicating the soil structure of the GM and GSM treatments was more stable than that of the CK and NPK treatments, which was confirmed by soil aggregate stability data. These results suggest manure should be used to improve soil structure and increase soil stability. We also recommend soil shrinkage curves as a useful tool to study the structural properties, dynamics, as well as the quality of the paddy soil with a high shrinkage capacity.

Soil Shrinkage Characteristics as Affected by Solution Composition and Mineral Contents

ABSTRACTSoil-shrinkage characteristics affect fluid transport and soil mechanical properties, with broad implications for environmental flows, crop production, and civil engineering designs. We quantified mild-saline-solutions effects on soil shrinkage curves and developed pedotransfer functions to predict curve parameters. Seven soil and soil mixes were equilibrated with solutions of 0.5-to-8 dS m−1 and 0-to-20 sodium adsorption ratios (SAR). Saturated paste rods were dried; water contents and isotropic shrinkage measured. Texture affected shape-forming factors when clay and smectite contents were >260 and 140 g kg−1, respectively. Solutions ≥2 dS m−1 affected the coefficient of linear extensibility for smectitic soils containing clay ≥300 g kg−1. Solution SAR affected only the highest clay content (530 g kg−1) and mixed mineralogy soils. However, the solution salinity levels were not high enough to affect shape factors of the shrinkage curves. Pedotransfer functions successfully described soil shrinkage with root-mean-squared-errors 1 to 4 magnitudes lower than the highest measured values.

Study on soil shrinkage characteristics during soil water characteristic curve measurement

Clay loam soil from Yunnan(KM),sandy loam soil from Liaoning(SY) and Xinjiang(KL),and loam soil from Shandong(LY) were selected for analyzing the characteristics of soil shrinkage duringsoil water characteristic curve measurement in order to explore the suitability of fitting models for soil watercharacteristic curve,and the changes of soil shrinkage. In this paper,soil water characteristic curves ofthe four soil types were measured by centrifuge method and were fitted by RETC software. The resultsshowed that as for KM,SY,KL and LY soils,firstly,soil moisture content gradually decreased with soilsuction increasing from 0 to 7000 cm. And the rate of soil water reduction decreased,and then increased,and then decreased again. Secondly,all fitting models presented in RETC software were of high accuracyfor the simulation of soil water characteristic curves,and the appropriate fitting models for KM,SY,KLand LY soils were VG-M(m,n),LND-M,VG-M(1-1/n,n) and VG-B(m,n),respectively. And VGmodel could be considered as the optimal model for simulation of soil water characteristic curves of thefour soils. Thirdly,a logarithmic function was found between degree of effective soil shrinkage and soil suc-tion during soil water characteristic curve measurement. The soil shrinkage was ranked in the order of SY KM LY KL,and the bulk density of the four soils increased by 0.19 ~ 0.46 g/cm3. Fourthly,soil shrink-age process could be roughly divided into pseudo-saturated stage,structural stage and super-normal stage.And as for KM,SY,KL and LY soils,the three stages could be described by linear function,but theranges of soil suction corresponding to three soil shrinkage stages were different.

Ultrasonic, Molecular and Mechanical Testing Diagnostics in Natural Fibre Reinforced, Polymer-Stabilized Earth Blocks

The aim of this research study was to evaluate the influence of utilising natural polymers as a form of soil stabilization, in order to assess their potential for use in building applications. Mixtures were stabilized with a natural polymer (alginate) and reinforced with wool fibres in order to improve the overall compressive and flexural strength of a series of composite materials. Ultrasonic pulse velocity (UPV) and mechanical strength testing techniques were then used to measure the porous properties of the manufactured natural polymer-soil composites, which were formed into earth blocks. Mechanical tests were carried out for three different clays which showed that the polymer increased the mechanical resistance of the samples to varying degrees, depending on the plasticity index of each soil. Variation in soil grain size distributions and Atterberg limits were assessed and chemical compositions were studied and compared. X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), and energy dispersive X-ray fluorescence (EDXRF) techniques were all used in conjunction with qualitative identification of the aggregates. Ultrasonic wave propagation was found to be a useful technique for assisting in the determination of soil shrinkage characteristics and fibre-soil adherence capacity and UPV results correlated well with the measured mechanical properties.