Mudstone Soil Research Articles

Deformation and strength degradation mechanism of weathered mudstone soil during dry-wet process based on a developed DEM approach

The soils suffer dry-wet cycles in nature and engineering due to the change of temperature, rainfall and the fluctuation of the groundwater level. The shrinkage-swelling deformation and mechanical properties evolve with the variations of moisture content during a dry-wet process was investigated by laboratory dry-wet cycle tests of a weathered mudstone soil. A DEM approach was developed for simulating the mechanical behaviors during the dry-wet process of the studied soil, considering the shrinkage-swelling deformation by adjusting the shrinkage or swelling ratio of the clay aggregate particles. The irreversible shrinkage-swelling deformation mechanism and the strength degradation mechanism were revealed. The results showed the developed DEM simulations can represent the deformation and the mechanical properties of soils during the dry-wet process. The shrinkage rate of soil decreases with the moisture content from saturation value to 5%, due to the reduction of the shrinkage potence of the clay aggregates. The irreversible shrinkage deformation of soils during a dry-wet process is because the limit swell potence of clay aggregate particles during the wetting process, leading to the swell during the wetting less than the shrinkage during the drying process. The strength degradation was divided into reversible portion mainly affect by the moisture content, and the irreversible portion affected by the meso-crack evolution during the dry-wet process. The large increase of meso-crack number during the drying leads to the rapid reduction of irreversible soil strength, while the decrease of porosity leads the increase of particle contacts and healing of the irreversible soil strength.

Groundwater Investigation Using Electrical Resistivity Imaging Technique in Western Ramadi, Iraq

The two-dimensional electrical resistivity imaging technique was used to examine groundwater in western Ramadi. The survey was performed with a factor (n) and a-spacing values of 6 and 5 m, respectively. The inverse models clearly show the resistivity variation between the anomalous parts of the water table and all the sediments. The vertical extension of the saturation sediments is between 1.5–9.5 m, which is identical to the groundwater level in the three existing wells located in the University of Anbar, with an area of 7 kilometers and an area of 18 kilometers. The extreme thickness of the water saturation layer was determined to be about 10.5 meters. It was concentrated in gypsum and mudstone soils with secondary gypsum and siltstone, considered the upper components of the Injana Formation at the University of Anbar. At 7 Kilometer area which starts from a depth of 1 m to depths of up to 12 m, it is also considered a groundwater reservoir. While 18 Km area is considered to have dry soil and the groundwater in it is far from the surface at 12 m depth.

Synergistic effects of colloidal nanosilica and fiber on the hydromechanical performance of mudstone soil in Taiwan

Synergistic effects of colloidal nanosilica and fiber on the hydromechanical performance of mudstone soil in Taiwan

Enhancing the mechanical and hydromechanical behaviors of mudstone soils using sugarcane press mud

Geological hazards, such as landslides and soil erosion, are frequently found in regions where mudstone soils are prevalent. These soils can also present challenges for the construction of infrastructure, including roads, railways, and other facilities. While various methods exist for addressing the mechanical and hydromechanical properties of mudstone soils, the reuse of waste materials may be a cost-effective alternative. This study presents the effect of press mud, a by-product of sugar purification, as an alternative material for improving the performance of mudstone soils. Unconfined compressive strength tests were conducted to evaluate the mechanical properties of untreated and press mud-treated mudstone soils. In addition, free swell tests, one-dimensional consolidation tests, and three-dimensional volumetric shrinkage tests were performed to investigate the hydromechanical properties of the soils. These tests provided insights into the behavior of the mudstone soils under various conditions. In addition, microstructural analysis such as X-ray diffraction, X-ray fluorescence, Fourier-transform infrared spectroscopy, and scanning electron microscopy were performed to identify the soil improvement mechanisms. The results demonstrated that press mud can act as a binder and help enhance the peak and postpeak strengths of mudstone soils. The swelling and shrinkage characteristics improved when it was treated with press mud; however, the inclusion of press mud slightly increased the compressibility of mudstone soils. According to microstructural analysis, the formation of extra cementitious gels helped enhance the mudstone soils performance. These findings offer promising and environmentally friendly options for effectively treating mudstone soils and address the needs of engineers seeking sustainable solutions.

Effects of hydrophilic and hydrophobic nanosilica on the hydromechanical behaviors of mudstone soil

In this study, the effects of hydrophilic (HPI) and hydrophobic (HPO) nanosilicas (NS) on the hydromechanical properties of mudstone soil were investigated in a laboratory. Mudstone soil samples treated with different contents (0.3%, 0.6%, 0.9%, and 1.2%) of both types of NS were prepared and rigorously examined through standard Proctor compaction, unconfined compression, three-dimensional volumetric shrinkage, and one-dimensional consolidation tests. In addition to the hydromechanical tests, nondestructive tests, including X-ray diffraction, X-ray fluorescence, and Fourier-transform infrared spectroscopy, were employed to inspect the geochemical and mineral composition of treated and untreated samples. Finally, scanning electron microscopy was used to monitor the packing state of the specimens. The experimental results reveal that the shrinkage and compressibility characteristics of mudstone soils can be significantly improved through NS treatment. In particular, the results demonstrate that the mudstone soils treated with 0.3% NS, regardless of type, had the highest compressive strength. Our results provide insight into the contribution of NS to the hydromechanical properties of mudstone soils and suggest that NS-HPI may be a better treatment than NS-HPO due to its improved ability to strengthen mudstone soils.

Effects of Biochar Application on Vegetation Growth, Cover, and Erosion Potential in Sloped Cultivated Soil Derived from Mudstone

Soil degradation is a crucial problem, particularly in tropical and subtropical areas. Prevention or reduction of soil erosion requires strategies based on thorough rapid vegetation cover (VC) and favorable soil quality in subtropical and tropical areas. This study applied wood biochar (WB) and rice husk biochar (RHB) in a mudstone soil, which is widely distributed in Southern Taiwan, to investigate the effects of biochar application on soil erosion and vegetation restoration. The standard erosion unit plots (22.13 m in length and 9% in slope gradient) were set up to determine the relationship among soil losses, VC, and natural rainfall characteristics with and without biochar application. The results indicated that biochar application increased the growth rate (identified by cover ratio) of Bahia grass (Paspalum notatum Flüggé) by 2–2.6 times within 40 days compared with control (without biochar application) and increased VC by 20% after 120 days of treatment. The biochar application could effectively reduce soil losses by 60% at least in the mudstone soil. A well-predicted regression function of soil loss with VC and rainfall kinetic energy was established (amount of soil lost = −0.435 × ln VC + 0.54 × RKE, r = 0.89, p < 0.01).

Clogging Risk Early Warning for Slurry Shield Tunneling in Mixed Mudstone–Gravel Ground: A Real-Time Self-Updating Machine Learning Approach

Clogging constitutes a significant obstacle to shield tunneling in mudstone soils. Previous research has focused on investigating the influence of soils and slurry properties on clogging, although little attention has been paid to the impact of tunneling parameters on clogging, and particularly early clogging warning during tunneling. This paper contributes to developing a real-time clogging early-warning approach, based on a self-updating machine learning method. The clogging judgment criteria are based on the statistical characteristics of whole-ring tunneling parameters. The paper proposes the use of random forest (RF) for a real-time self-updating early warning strategy for clogging. The performance of this approach is illustrated through its application to a slurry-pressure-balanced shield tunneling construction of Nanning metro line 1. Results show that the RF-based approach can predict clogging during a ring construction with only four minutes of tunneling data, with an accuracy of 95%. The RF model provided the best performance compared with the other machine learning methods. Furthermore, the RF model can realize an accurate clogging prediction in one ring, using less tunneling data with the self-updating mechanism.

Morphological traits and root anchorage ability of native pioneer tree species for reforestation of mudstone badlands

ABSTRACT Mudstone badlands occupy a large area in southwestern Taiwan. Mudstone soils with poor cementation property are particularly vulnerable to water erosion and landslides during rainy seasons. Broussonetia papyrifera, Hibiscus taiwanensis and Macaranga tanarius are major pioneer tree species occurring on mudstone badlands. Therefore, these species are beneficial for slope stabilization and forest restoration to control erosion and landslide. Nevertheless, information on their morphological traits and root biomechanical properties are lacking. In this research, root morphological traits of these species were inspected utilizing WinRHIZOPro Image Analysis System. Root anchorage ability and root tensile strength of 1-year-old B. papyrifera, H. taiwanensis and M. tanarius saplings were evaluated using uprooting testing and root tensile testing. The results show, compared to H. taiwanensis, B. papyrifera and M. tanarius plants had markedly greater root traits. Moreover, the root anchorage abilities of M. tanarius and B. papyrifer plants were notably higher than that of H. taiwanensis. In addition, root tensile strength of M. tanarius plants was markedly higher than those of B. papyrifera and H. taiwanensis plants. The results clearly demonstrate that M. tanarius outperforms B. papyrifera and H. taiwanensis, in these traits. Taken together, the priority for selecting these species for reforestation of mudstone badlands follows as: M. tanarius > B. papyrifera > H. taiwanensis. These results, together with the information on ecological succession following erosion and landslide, allow us to develop the reforestation plan and management strategy of mudstone badlands.

Effect of clay minerals on the suction stress of unsaturated soils

The primary objective of this study is to investigate the characteristics of suction stress in two types of unsaturated weathered soils with different clay minerals. To obtain the mineralogical properties of the two samples, X-ray diffraction and scanning electron microscope analyses were conducted, and a large amount of kaolinite and montmorillonite was subsequently contained in the granite soil and mudstone soil, respectively. The granite soil was first remolded to obtain the same relative density and particle size distribution as the mudstone soil, and an automated soil-water characteristic curve (SWCC) apparatus was used to measure the water content and matric suction. The weathered granite soil had a higher air-entry value, and the volumetric water content was significantly changed by small changes in matric suction. The weathered mudstone soil showed a large hysteresis in the SWCCs between drying and wetting processes because of the ink-bottle effect, contact angle effect, and trapped air. The suction stress characteristic curve (SSCC) demonstrates that weathered mudstone soil had a larger magnitude of suction stress. The SSCCs of the weathered granite and mudstone soils display similar tendencies to the SSCCs of silt and clay, respectively. Therefore, the unsaturated characteristics considerably depend on the clay mineral composition and particle size distribution.

A novel 2-D ring-tubes model and numerical investigation of heat and moisture transfer around helix ground heat exchanger

As for the helix ground heat exchanger, a novel 2-D ring-tubes heat and moisture transfer model was built in this paper for the sake of efficiency and convenience. And a miniature model experiment was conducted to verify the correctness of the model. Four different soil initial water content conditions were simulated with the established model. In addition, the novel model was compared with the pure heat transfer model of which there is no moisture migration. The results indicate that increasing the initial soil water content can increase heat transfer capacity of the exchanger effectively. Three different heat transfer stages can be divided for the helix ground heat exchanger in the water flow direction. And during the design of exchanger, the proportion of entrance and exit stages should be increased for the sake of larger heat exchange capacity. Moreover, some effective measures can be conducted to increase soil water content near the entrance stage in order to avoid excessive reduction of soil water content in this area. There is a critical initial water content θcr for heat release condition to determine the applicability of the pure heat transfer model, and it’s 0.111 m3/m3 for the typical mudstone soil in Chongqing.

Size effect on mudstone strength during the freezing–thawing cycle

A series of single-particle crushing tests was carried out to investigate the size effect of coarse-grained mudstone soil strength with three categories of nominal particle size, 2·5, 5·0 and 10·0 mm, during various numbers of freezing–thawing cycles. On the basis of test results, the main crushing mode of a single mudstone grain and the correlation between the given characteristic stress and the probability of survival were determined. The results also indicated that the strength of a single particle decreases with increasing nominal particle size and an increasing number of freezing–thawing cycles. Moreover, the Weibull modulus was calculated to examine the applicability of the Weibull distribution on the single-particle failure strength of a mudstone grain. The results revealed that the Weibull modulus decreases slightly with an increase in the number of freezing–thawing cycles, and the test data are accurately described by the Weibull distribution. It was further concluded that the relationship between particle size and characteristic stress and the average failure force, considering the Weibull modulus, can be predicted by the size effect.

Sedimentary Marl mudstone as a substrate in a xeric environment revealed by microbiome analysis.

The sedimentary Marl mudstone soil is composed primarily of CaCO3, and is an important pedologic and geomorphologic element known as Marl, extensively dispersed in slopes and ridges in the northern Negev Desert, Israel. The wide Marl soil-layer areas are barren, with well-developed streamsides and no perennial vegetation cover. Soil systems in the Negev Desert have been widely studied, yet very little information was collected on Marl soils, and even less on the microbiome present in the Negev. Thus, an evaluation of the microbial-community inhabitants in a Marl soil layer was conducted in an attempt to distinguish between Marl with surface green mat and bare Marl soil layer. Our objective was to investigate the microbiome and abiotic components of the upper layer (0-5cm) of Marl and Marl-with-green-mat soil collected in the Negev Desert. Plate-counting enabled the estimation of fungal and bacterial population size, while nested polymerase chain reaction (nPCR) and Ion Torrent sequencing were used to analyze biological diversity. The results indicate significant differences in microbial biomass and microbial-community diversity between Marl and Marl-green mat, despite similar pH levels. Further study is needed to enhance understanding of the activity of the biotic components and their contribution to slope stabilization.

Preliminary research on the theory and application of unsaturated Red-layers embankment settlement based on rheology and consolidation theory

The settlement of an embankment body is always a significant technological issue in highway and railway construction. The embankment body is usually constructed using unsaturated soil, whose deformation consists of three parts, instantaneous deformation, primary-consolidation deformation and secondary-consolidation deformation. The primary consolidation and the secondary compression deformations are not two separate processes, but they influence each other, that are the deformation of the embankment body is the coupling-effect result of unsaturated-rheology and consolidation. Based on the results of uniaxial compression creep test of crushed Red-layers mudstone soils and the principle of the single stress state variable in unsaturated soils, the theory of unsaturated embankment settlement of Red-layers is put forward. Physical centrifugal tests and numerical simulation of centrifugal loading process are adapted not only to study the relationships of the settlement of the embankment body filled with different compaction coefficients versus embankment filling height, as well as the settlement after construction versus time, but also to predict the settlement after construction. Based on these studies, a project case, the settlement characteristics of a section of the railway line for passenger traffic from Chongqing to Suining have been studied by numerical simulation considering actual filling process. These show that the physical centrifugal tests and site monitoring data largely coincide with the corresponding numerical simulation results, showing the high validation of the proposed coupling-theory.

Impacts of biochar on physical properties and erosion potential of a mudstone slopeland soil.

Food demand and soil sustainability have become urgent issues recently because of the global climate changes. This study aims to evaluate the application of a biochar produced by rice hull, on changes of physiochemical characteristics and erosion potential of a degraded slopeland soil. Rice hull biochar pyrolized at 400°C was incorporated into the soil at rates of 2.5%, 5%, and 10% (w/w) and was incubated for 168 d in this study. The results indicated that biochar application reduced the Bd by 12% to 25% and the PR by 57% to 92% after incubation, compared with the control. Besides, porosity and aggregate size increased by 16% to 22% and by 0.59 to 0.94 mm, respectively. The results presented that available water contents significantly increased in the amended soils by 18% to 89% because of the obvious increase of micropores. The water conductivity of the biochar-amended soils was only found in 10% biochar treatment, which might result from significant increase of macropores and reduction of soil strength (Bd and PR). During a simulated rainfall event, soil loss contents significantly decreased by 35% to 90% in the biochar-amended soils. In conclusion, biochar application could availably raise soil quality and physical properties for tilth increasing in the degraded mudstone soil.

불포화 이암풍화토에서의 흡입응력 이력현상

본 연구에서는 포항지역의 자연사면에서 채취된 이암풍화토(CL)의 흡입응력 이력현상을 조사하기 위하여 자동 흙-함수특성곡선(SWCC) 측정장치를 이용하여 건조 및 습윤과정에 따른 모관흡수력과 체적함수비를 측정하였다. 시료에 모관흡수력을 재하시켜 간극수를 유출시키는 건조과정과 반대로 모관흡수력을 제하시켜 간극수를 유입시키는 습윤과정을 재현하였다. 측정결과를 토대로 van Genuchten(1980)의 방법을 이용하여 흙-함수특성곡선(SWCC)을 산정한 결과 유효포화도에 따른 모관흡수력은 비선형적인 관계를 나타내며, 건조 및 습윤과정을 거치는 동안 동일한 유효포화도에서 다른 모관흡수력을 나타내는 이력현상(hysteresis)이 발생되었다. 그리고 Lu and Likos(2006)의 방법을 이용하여 흡입응력특성곡선(SSCC)을 산정한 결과 낮은 모관흡수력에서 흡입응력은 빠르게 증가하며 이후 미소하게 증가하는 것으로 나타났으며, 동일한 모관흡수력에서는 건조과정의 흡입응력이 습윤과정의 흡입응력보다 크게 나타내는 이력현상이 발생되었다. 따라서 불포화토의 특성을 고려하여 설계 및 안정성 검토를 수행하는 경우 강우침투시에는 습윤과정의 흡입응력특성곡선(SSCC)을 적용하고, 건조 혹은 배수시에는 건조과정의 흡입응력특성곡선(SSCC)을 적용하는 것이 바람직하다. To investigate the hysteresis of the suction stress in unsaturated weathered mudstone soils (CL), matric suction and volumetric water content were measured in both drying and wetting processes using Automated Soil-Water Characteristics Curve Apparatus. The drying and wetting processes in unsaturated soils were reproduced in the test; the drying process means to load matric suction to spill pore water from the soils, and the wetting process means to unload matric suction to inject pore water into the soils. Based on the measured result, Soil Water Characteristic Curve(SWCC)s were estimated by van Genuchten model (1980). SWCCs have nonlinear relationship between effective degree of saturation and matric suction. The hysteresis in SWCCs between drying and wetting processes occurred. As a result of estimating Suction Stress Characteristic Curve(SSCC) using Lu and Likos model (2006), the suction stress rapidly increased in the low level of matric suction and then increased slightly. Also, the hysteresis in SSCCs between drying and wetting processes occurred. In order to design geo-structures and check its stability considering unsaturated soil mechanics, therefore, it is more reasonable that the SSCC of drying process should be applied in the condition of rainfall infiltration and the SSCC of wetting process in the condition of evaporation or drainage.

Hillslope runoff and erosion on duplex soils in grazing lands in semi-arid central Queensland. II. Simple models for suspended and bedload sediment

The use of simple models of soil erosion which represent the main effects of management in grazing lands in northern Australia is limited by a lack of measured parameter values. In particular, parameters are needed for erosion models (sediment concentration v. cover equations) used in daily soil-water balance models. For this research, we specifically avoided equations that use rainfall and runoff rates (e.g. peak flow), as current daily models are limited in their ability to estimate these rates. The resulting models will therefore give poor estimates of soil losses for individual events, but should give good estimates of long-term average erosion and management influences. Runoff and erosion data were available for 7 years on 12 hillslope plots with cover of 10–80%, with and without grazing, with and without tree canopy cover, on a variety of soils according to various soil classification systems. Soils were grouped into those derived from sandstone (SS), mudstone (MS), and eroded mudstone (MSe). These data were used to determine two parameters, i.e. (i) efficiency of entrainment for bare soil and (ii) a cover factor, for simple models of bedload and suspended sediment concentrations. Methods used to fit parameters affected the results; optimising to obtain the minimum sum of squares of errors in soil losses gave better results than fitting an exponential equation to sediment concentration–cover data. The use of a linear slope factor in the sediment concentration models was confirmed with data from plots with slopes 4–8%. Parameters for the bedload sediment concentration model were the same for SS, MS, and MSe soils. Parameters for the suspended sediment concentration model were the same for SS and MS soils, but the MSe soil had a greater efficiency of entrainment for bare soil (about double). The sediment concentration–cover relationships and fitted cover factors were different for suspended and bedload sediment. Thus, the resulting modelled proportion of sediment as suspended load changed with cover, from ~0.3 for bare soil to 0.9 at 80% cover, mimicking the measured data. The cover factor was lower than published values for cultivated soils, indicating less reduction in sediment concentration with greater cover. A compilation of parameter values for the sediment concentration model from published and unpublished sources in grazing and cropping lands is provided.

Erosion control for mudstone soil with ventilation and watertight resin

To accelerate the re-vegetation of exposed landslide areas, hydroseeding for soil and water conservation has been widely applied as one of the economically feasible ways. However, effect durations of different hydroseeding materials are different, the formulation density has a certain effect on plant growth and the addictives may exude. This paper presents laboratory experiments of soil erosion, exuding water quality and soil hardness by using a rainfall simulator with different conditions of slope, rainfall intensity and medication density. The results showed that soil erosion decreased significantly, suggesting a good erosion-resisting effect by the ventilation and watertight resin. No significant variation of the exuded water was observed during testing, which indicates that after gelling, the ventilation and watertight resin are unlikely to release chemical substances. It was found that high resin density will result in poor workability as well as high costs; adverse will cause the mudstone to fracture due to raindrops since cracks are common to soil surface. The weatherability after spraying and its effect on plant vegetation still need further investigation.

Potential and Pitfalls in Establishing the Provenance of Earth‐Related Samples in Forensic Investigations

Earth scientists are often asked to establish or constrain the likely provenance of very small quantities of earth-related material as part of a forensic investigation. We tested the independent and collective interpretations of four experts with differing analytical skills in the prediction of sample provenance for three samples from different environmental settings. The methods used were X-ray diffraction, scanning electron microscopy, the assessment of pollen assemblages, and structural characterization of organic matter at the molecular level. Independent interpretations were less accurate than those where multiple techniques were combined. Collective interpretation was very effective in the assessment of provenance for two of the three sites where the mineralogy and plant communities were distinctive. At the other site, although the mineralogical analysis correctly identified the Triassic mudstone soil parent material, Carboniferous spores from domestic coal were initially interpreted as deriving directly from bedrock. Such an interpretation could be a common pitfall owing to anthropogenic redistribution of material such as coal.

Effect of NaCl solution as pore water on the residual shear strength and index properties of soil from mudstone areas

NaCl solution has significant effect on the residual shear strength of soil from mudstone areas. Soil samples were collected from the intact rock (unsheared zone) and sliding surface (sheared zone) of five mudstone landslide areas. Mixtures of distilled water and the intact rock possessed higher electric conductivity than those of distilled water and the sliding surface soil. When these samples were leached with distilled water for five times, they showed a substantial decrease in the electric conductivity. The residual shear strength varies according to the NaCl concentration in the pore water. Ring shear tests were also carried out in the commercial standard clays as bentonite and kaoline to understand the shear strength characteristics of the mudstone soils. When bentonite was treated with NaCl solution as pore water, it showed about three times increase in residual shear strength and decrease to one quarter in liquid limit. The effect of NaCl solution as pore water in kaoline was comparatively low. The residual shear strength of soil from mudstone area also increased when it was treated with NaCl solution as pore water. The result of the X-ray diffraction analysis showed that the proportion of smectite is higher than that of kaolinite in the residual soil from mudstone. These smectite minerals were found to be highly sensitive to NaCl solution. Because of the sensitive changing character of smectite minerals to NaCl solution, soil samples with NaCl rich water showed lower value in consistency limits and higher value in the residual shear strength compared to soil samples with distilled water. The findings suggest that the residual shear strength and index properties should be considered as variable properties as a result of the change in the pore water. Such properties are useful to understand frequent re-activation of the landslide occurring in the mudstone areas.