Consolidation Properties Research Articles

Strength and consolidation properties of clay modified by nano bentonite

Nano bentonite is a new kind of soil modification material, which can effectively improve the physical and mechanical properties of clay. The development of new soil modification technology has been a research hotspot in geological engineering, geotechnical engineering and road engineering. The purpose of this study is to test and analyze the strength and consolidation characteristics of clay modified by nano bentonite, and to explore the new clay materials applied in modern geological engineering. In this study, an installation test was carried out on the preparation of nano bentonite, and the compressive condition of the bentonite was observed. After that, the viscosity strength of nano bentonite was compared with that of undisturbed soil by the control variable method, and the nano bentonite was divided into experimental group and control group. The viscosity strength and consolidation characteristics of nano bentonite were observed and analyzed by changing temperature, nano bentonite content, pressure and pore ratio. The results show that the consolidation coefficient of the sample without adding nano bentonite is 8.7 × 10–3 cm2/s, which is 6.6 × 10–3 cm2/s lower than that of 2% nano bentonite. It shows that the consolidation coefficient decreases with the increase of consolidation pressure and the decrease of void ratio. The nano bentonite modified clay is also more stable in road or building construction. The method of this study has brought a certain value for the research of nano materials in soil materials.

Preventing the Undesired Surface Veiling after Nanolime Treatments on Wall Paintings: Preliminary Investigations

During the last decades, the discovery of nanolime and its introduction in the field of Cultural Heritage has entailed a significant advance for the consolidation of historic wall paintings. Nevertheless, its use is not completely generalized yet within the conservation practitioner’s community due to its undesired white veiling deposit on the surface after treatment which usually covers the pictorial layer. Given the scarcity of existing literature which specify how to mitigate this undesired side-effect, the aim of this work is to carry out the first assessment of possible cleaning and treatment methods to eliminate those deposits and, at the same time, to analyse their effects on the consolidation properties. To do that, we have developed laboratory fresco wall paintings specimens. After applying an artificial ageing cycle to all of them, we consolidated them with CaloSil IP25, one of the most currently used commercial product in the practice. The elimination of the whitish deposits has been investigated with different methods: (1) wiping off the superficial excess of product immediately after each application during the treatment; (2) mechanical cleaning (scalpel) after consolidation; chemical cleaning with rigid gels of water (3), ethylenediaminetetraacetic acid (EDTA) (4) and citric acid (5) after consolidation. The effectiveness of each cleaning method has been assessed by non-destructive methods before and after the consolidation, and repeated after cleaning, by measuring differences in colour, water absorption by capillarity (i.e., sponge test), superficial adhesion (i.e., Scotch Tape Test) and by quantifying the thickness of the deposits eliminated by means of photogrammetry. Results show that both the mechanical cleaning and the removal of the excess of product after each application during the treatment yielded the most promising results for conservation practice.

Consolidation properties and structural alteration of Old Alluvium

We present experimental observations and a conceptual model for understanding the compression and swelling characteristics of Old Alluvium (OA) from San Juan, Puerto Rico. Prior studies have classified OA as a transported, in situ weathered tropical soil whose intact macrostructure comprises a cemented, pseudo-silt with a mixture of quartz grains and aggregated clay particles. The aggregates include mixtures of kaolinite and smectite coated by Fe-oxides. The Fe-oxides also act as cementing agents between the particles. This study describes results from a series of high-pressure (up to 63 MPa) incremental consolidation tests. Breakdown of the clay aggregates and cemented structure is observed through changes in the compression properties, significant swelling during unloading, and an extraordinary reduction (i.e., by three orders of magnitude) in the coefficient of consolidation. These experimental observations are explained by a combination of mechanical processes, comminution and breakdown of cementing bonds, and physicochemical changes linking pore fluid in the intra- and inter-aggregate pore space. These processes alter the fundamental particle size distribution and macro-porosity of the soil and activate the swelling potential of the smectites concealed by the Fe-oxides coating in the intact material. The experimental observations provide the basis for the formulation of a constitutive model to describe macroscopic compression and swelling behavior of Old Alluvium and offer a framework to understand the response of piedmont transported residual soils found elsewhere.

Design of Novel Photocatalytic Films for the Protection of Architectural Surfaces via the Incorporation of Green Photocatalysts

In conservation science the demand of multifunctional green materials displaying water repellency, consolidation, resistance to organic pollutants and pigments is constantly increasing. This research developed a green nanocomposite exhibiting photocatalytic, hydrophobic, consolidation and self-cleaning properties. This was achieved by synthesizing a TiO2 photocatalyst enriched with carbon dots (C-dots) and successfully incorporated into a tetraethoxysilane nanocomposite modified with nano-calcium oxalate and polydimethylsiloxane. The TiO2/C-dots that were prepared with a simple, low temperature, cost-effective and large-scale procedure were assessed via analytical and spectroscopic techniques and were resulted in anatase structure ranging in size from 10 to 40 nm. Photooxidation measurements displayed that TiO2/C-dots nanoparticles could photodegrade completely Methyl Orange (MO) under UV and visible irradiation after 120 min. The photocatalytic performance of the nanocomposite with TiO2/C-dots resulted promising under UV after longer irradiation time. The degradation of MO was faster on bulk xerogels containing the TiO2/C-dots than the corresponding ones with TiO2. The treatment of concrete, limestone and lime mortars with the nanocomposite proved to be compatible with the substrates in terms of aesthetical aspects. This study demonstrates encouraging potential for large-scale production of a multifunctional protective composite that offers hydrophobicity, self-cleaning properties and consolidation to architectural surfaces.

Mechanism of Bound Water Effects on the Secondary Consolidation Property of Soft Soil

Mechanism of Bound Water Effects on the Secondary Consolidation Property of Soft Soil

Two-dimensional plane strain consolidation for unsaturated soils with a strip-shaped distributed permeable boundary

The preloading consolidation method has been widely applied to ground treatment. In this case, the top surface of unsaturated soil stratum is fully covered with a geosynthetics blanket to aid water and air flowing from the soil, which may cause uneconomic and wasteful design. This paper presents semi-analytical solutions of two-dimensional (2D) plane strain consolidation for unsaturated soils with a strip-shaped distributed permeable boundary. Based on the 2D consolidation theory proposed by Dakshanamurthy and Fredlund (1980), semi-analytical solutions of excess pore pressures and settlement in Laplace domain are derived by jointly adopting Fourier sine series, Laplace transformation, and differential operator method. Then, the analytical solutions in the time domain are derived and the corresponding computing program is developed based on Crump’s method. The validity of obtained solutions has been conducted by comparing the current solutions with those under the permeable top boundary in the literature. A series of calculating examples are performed to study the consolidation properties under a strip-shaped distributed permeable boundary. Parametric studies are carried out for the 2D distribution of excess pore pressures and settlement considering the coverage percentage of geosynthetics, anisotropy consolidation coefficient, the width and thickness of unsaturated soil stratum.

Effect of cement dust on consolidation properties of expansive soil

The utilization of by-product wastes as stabilizer materials to problematic soils has become widely common. Such a situation considers as a solution to the negative effects of these materials on the environment, on one hand, and as an economic solution by recycling the wastes in soils’ improvement techniques, on the other. The purpose of the present study is to explore the consolidation properties of Iraqi expansive soil with the addition of one selected by-product wastes materials from the local industry process. The cement dust has been selected as a stabilizer to explored expansive soil. The cement dust has been selected as a stabilizer to explored expansive soil. The cement dust is a waste of cement industry and its deposit is rarely recycled in the local Iraqi industry, and there are significant amounts of cement dust available as waste materials. Herein, the specimens were prepared by mixing the expansive soil with different content of cement dust (from 0% to 30%). An experimental series of consolidation tests were carried out to explore the effects of cement dust on consolidation properties experienced by expansive soil. Test results indicate that cement dust has considerably affected the consolidation properties of expansive soil. In particular, the swelling index (cs) was reduced for one-third of the value of cs of virgin soil.

Riverbed fluctuation and erosion property of cohesive sediment based on long-term topographic surveys in a macrotidal estuary

The feature of large scouring process of cohesive sediment and the long term seasonal riverbed fluctuation at the estuarine turbidity maximum (ETM) zone of the macrotidal Chikugo River estuary, Japan were studied using the intensive periodical transverse surveys of riverbed topography and sediment sampling along with continuous monitoring of water level, salinity and turbidity during 2005–2017. The results revealed that substantial erosion occurs (increase in channel capacity) when the river discharge exceeds 2,000 m3 s−1 while deposition occurs (decrease in channel capacity) when the flow falls under 100 m3 s−1. During the normal flows, the bed shear stress (values ranging from 0.2–4.0 N m−2) showed a harmonious behavior driven by the fortnightly tidal variations. Conversely, rapid variations in bed shear stress values (2.0–22.7 N m−2) were observed during the flood events. Further, a critical shear stress value of 1.8 N m−2 was estimated as the erosion threshold of mud deposit in the estuary. Finally, an erodibility coefficient of 0.0015 s2 m−2 was determined based on the reasonable relationship (R2=0.767) between erosion depth and accumulated friction velocity from the actual field data. This value is several times lower than those reported in previous studies due to the differences in deposition and consolidation properties of sediments between actual and experimental channels. This indicates that the erosion of cohesive sediments in estuaries is not only influenced by the magnitude of shear velocity, but also by its consolidation characteristics.

Evaluation of candidate polymers to maximize geotechnical performance of oil sands tailings

Oil sands fluid fine tailings deposits are challenging to reclaim due to their inherently high natural water content, low permeability, and low strength. Combinations of polymers and (or) coagulants are used by operators to improve the dewatering and strength properties of the tailings. However, considerably more work has been done to evaluate polymer performance with short-term dewatering metrics rather than with long-term metrics such as consolidation properties. This paper evaluates the potential of four novel polymers for use in fluid fine tailings treatment compared to a commercially available polymer and untreated tailings specimen. The performance of the polymers was assessed through initial screening with respect to short-term dewatering, evaluation of the consolidation and strength properties using large-strain consolidation tests, shear sensitivity in pipeline transport, and finally, large-strain consolidation modelling to appraise the relative potential performance under different strategies, such as terrestrial or aquatic reclamation options. One polymer exhibits remarkably fast dewatering at high void ratios, while another demonstrates dense and shear-resistant flocs. The paper discusses each polymer’s distinctive tailings fabrics and how their unique merits and limitations would benefit different reclamation eventualities. Finally, potential improvements of the polymers are suggested for future assessment.

Effects of freeze-thaw and chemical preconditioning on the consolidation properties and microstructure of landfill sludge

At present, a large amount of landfill sludge(LS) has been accumulated all over the world. For environmental and engineering purposes, there is an urgent need for deep dewatering and volume reduction of LS. The deep dewatering of LS mainly uses the method of chemical preconditioning and mechanical dewatering, which is easy to cause environmental pollution and is not conducive to the subsequent resource treatment of LS. To find a more environmentally friendly and efficient method for deep dewatering of LS, an in-situ treatment method combining freeze-thaw and vacuum preloading was proposed. In this paper, based on the existing research, through compression consolidation test and MIP, SEM micro test, the consolidation properties and microstructure of LS after freeze-thaw and chemical preconditioning were studied, and the vacuum consolidation principle of different preconditioning was explored. The results show that: Both FeCl3 and freeze-thaw preconditioning can increase the permeability coefficient and consolidation coefficient by one to two orders of magnitude; After freeze-thaw preconditioning, the void ratio of sludge decreases and the permeability coefficient increases; Under low consolidation pressure, the mechanical properties of the two kinds of pretreated sludge changed significantly; The original sludge is mainly composed of small pores. After FeCl3 conditioning, the large pores and mesopores increased significantly, while the small pores decreased. After freeze-thaw, the large pores and mesopores increase greatly, while the small pores decrease greatly; The original sludge is in the form of a dispersive flocculent structure with many impurities. After freeze-thaw, the intercluster pores increase, showing a honeycomb structure. After FeCl3 conditioning, the sludge structure is more compact and uniform. The change of microstructure and consolidation characteristics of sludge after conditioning reflects the difference of two different preconditioning mechanisms.

Recycling the waste dolomite powder with excellent consolidation properties: Sample synthesis, mechanical evaluation, and consolidation mechanism analysis

Alkali activation has gradually become an important means to treat solid waste and produce green cementitious materials. The alkali-activated samples were successfully prepared by waste dolomite powder, whose consolidated-performance and environmental friendliness are both excellent. This work intensively investigates the preparation process and thermo-mechanical properties of alkali-activated waste dolomite powder, and emphatically analyses the consolidation mechanism, which is distinct from that of silicate alkali-activated materials. The optimal preparation parameters were found as follows: alkali concentration (1.5 wt%), compression molding pressure (125 MPa), curing temperature (could be from 22 to 150 °C), and holding time (2 h); under these preparation parameters, the corresponding samples’ compressive strength could reach a level between 67.77 MPa and 73.75 MPa. And its heat-resistance temperature is at least 400 °C, which is higher than that of Ordinary Portland Cement. Via the characterization analysis including TG-DTA, FTIR, XRD, SEM, and EDS, two-part mechanisms were suggested that may support this performance: the consolidation mechanism at room temperature (22 °C) was considered to involve two kinds of chemical reactions that were dedolomitization and ion cross-linking, and the thermal reaction was believed to contain the decomposition of magnesite and then of calcite. These results exhibit the alkali-activated waste dolomite powder has excellent mechanical properties and heat-resistance temperature, which not only provides an efficient, green path for waste dolomite powder handing but also renders a novel idea in the alkali-activated system based on dolomite.

Two-dimensional consolidation analysis of geotextile tubes filled with fine-grained material

In this study, a two-dimensional consolidation solution for geotextile tubes filled with fine-grained material was presented. The solution is based on a combination of various methods that were modified or extended to take into account the change in tube shape, the nonlinear interaction between the soil and geotextile, and the water content distribution of the tube during consolidation. Using the proposed solution, the effect of various necessary input parameters was investigated. Thereafter, numerous dewatering and consolidation properties of various combinations of geotextiles and fill materials were obtained from several tests such as the half cross-section test, hanging bag tests, and geotextile tube demonstration test. Results of the study have shown that the method presented in this study can well-represent the consolidation behavior of geotextile tubes filled with fine-grained material.

The Role of Nano Particles in Cancer Immunotherapy

Nanotechnology has been widely read and abused for malignant growth treatment as nanoparticles can play a significant part as a medication conveyance framework. Contrasted with regular medications, nanoparticle-based medication conveyance has specific favourable circumstances, for example, improved security and biocompatibility, upgraded porousness and maintenance impact, and exact focusing on. The application and improvement of half breed nanoparticles, which joins the consolidated properties of various nanoparticles, has driven this kind of medication transporter framework to the following level. Furthermore, nanoparticle-based medication conveyance frameworks have been appeared to assume a part in defeating malignancy related medication obstruction. The components of malignancy drug obstruction incorporate overexpression of medication efflux carriers, deficient apoptotic pathways, and hypoxic climate. Nanoparticles focusing on these components can prompt an improvement in the inversion of multidrug opposition. Moreover, as more tumour drug opposition instruments are uncovered, nanoparticles are progressively being created to focus on these systems. Moreover, scientists have recently started to investigate the role of Nano particles in immunotherapy, which assumes a more significant part in disease treatment. In this survey, we examine the parts of nanoparticles and cross breed nanoparticles for drug conveyance in chemotherapy, directed treatment, and immunotherapy and depict the focusing on instrument of nanoparticle-based medication conveyance just as its capacity on turning around drug obstruction.

Water resistance and compressibility of silt solidified with lime and fly-ash mixtures

Silt has poor engineering properties, and lime and/or fly ash are widely used to treat silt. However, very few studies could be found to investigate the water resistance and compressibility of lime and fly-ash mixtures (lime–FA) solidified silt. This paper investigated the unconfined compressive strength (UCS), water resistance and consolidation properties, and the microscopic characteristics of lime–FA solidified silt. In addition, the paper also compared the UCS, water resistance of lime–FA and lime solidified silt in our previous studies. Results reveal that the UCS increased slowly with increasing lime–FA dosage at 7 and 28 days of curing, but increased rapidly at 90 days of curing. However, at 7 days of curing, the soaked UCS was 0, and the water resistance was not improved by increasing lime–FA dosage. As the curing time increased, the UCS gain rate of different dosages of lime–FA solidified silt was largely consistent during 7–28 days of curing, but UCS gain rate became bigger when lime–FA dosage increased during 28–90 days of curing. Meanwhile, the water resistance coefficient increased first and then stabilized with curing time. Compared with lime solidified silt, the lime–FA stabilized silt had superior water resistance and a higher UCS gain rate, and the change trend of water resistance coefficient with curing time was basically the same as that of alone lime. In addition, the compressive modulus increased with curing time increasing, and microscopic analysis shows that the silt had a denser structure and more hydrates were formed with lime–FA dosage and curing time increasing.

The effect of temperature on some engineering and consolidation properties of soft soil

This article defines the effect of temperature on some engineering and consolidation properties of soft soil. The purpose of this research, therefore, was to determine the technical characteristics of soft clay consolidation behavior, specifically in terms of temperature influence on varying values of soil established mechanical parameters, including soft soil compression index (Cc), swelling index (Cs), volume change coefficient (mv), consolidation coefficient (Cv), and the permeability coefficient (k). In this analysis, the use of soft clay in an undisturbed condition was sourced from a swampy location in South Kalimantan Province, Indonesia. Also, the temperatures applied to the specimens were 22o C, 40o C, 60o C, and 70o C. The results showed the influence of temperature modifications on soil compressibility, where extensive heat was responsible for abundant soil compressibility. In addition, the associated parameters, termed soil compression index value (Cc), consolidation coefficient (Cv), and the swelling index (Cs), observed an increase by 3%, 33%, and 22%, respectively. Furthermore, existence of high temperatures limited the unstable soil volume, where the volume change coefficient (mV) tends to decrease by 3%. Also, varying temperatures essentially altered soil permeability, where the seepage properties of soft clay showed the tendency to increase by 32%, with rising soil temperature.

Study on the consolidation properties of soft soil distributed in the North Center coastal area of Vietnam

Consolidation parameters of soft soil play an important role in calculating settlement and soft soil improvement by vertical drainage method (distance, quantity, treatment time). In this study, using oedometer tests, consolidation parameters of some soft soils in the North Central coastal region, Vietnam are clarified. The research results show that the compression index Cc has a strong relationship with the natural water content, liquid limit, dry unit weight, and void ratio of the soil. The consolidation coefficient significantly depends on the applied pressure level, at the over-consolidation stage (normal stress is less than pre-consolidation pressure), the consolidation coefficient is high. By contrast, at the normal consolidation stage (normal stress is greater than pre-consolidation pressure), the coefficient of consolidation is small. The pre-consolidation pressure of soil changes with the distribution depth.

Microstructures and mechanical properties of a modified 9Cr ferritic-martensitic steel in the as-built condition after additive manufacturing

A newly developed nano-structured high-Mn 9Cr ferritic-martensitic (FM) steel designed for additive manufacturing (Additive-manufactured Nanostructured Alloy, ANA) was fabricated via the direct energy deposition method. The as-printed ANA2 showed tensile properties (strength and elongation) and Charpy impact toughness (upper-shelf energy and ductile-brittle transition temperature) comparable to oxide-dispersion-strengthened (ODS) Eurofer and PM2000. Compared with wrought P91, the as-built ANA2 showed significantly higher yield strength but inferior Charpy impact toughness and ductility. Microstructural characterization revealed uniformly distributed sub-micron pores, an extremely high dislocation density, and a high density of ultrafine nano-structured precipitates in the matrix. The microstructures indicated the dislocations as the dominant strengthening element and the ultrafine precipitates as the primary contribution to estimated irradiation sink density. This work demonstrates the ability to exploit the unique consolidation properties of additive manufacturing to fabricate steels which marry the benefits of both ODS alloys and conventionally processed FM steels.

Effect of compaction delay on the strength and consolidation properties of cement-stabilized subgrade soil

Soil compaction is a considerable construction activity to ensure safety and durability, notably in the transportation industry. Compaction delay (CD) occurs because of unpredictable cases which may be related to the climatic, environmental, and logistics reasons. Since the time delay in compaction process affects the engineering properties of the materials in road construction, the current study evaluates the effect of CD on mechanical and consolidation characteristics of cement-stabilized subgrade soil. To achieve this purpose, a set of experimental tests including standard compaction, unconfined compressive strength (UCS), and one-dimensional consolidation tests are performed. Samples are mixed with 1.5, 3, 6, and 9% Portland cement on their maximum dry density (MDD) considering different ranges of CD up to 120 min. Delayed samples show a reduction in MDD (3.46–5.43%), and UCS (11.31–37.25%) compared with those of non-delayed ones. Morphological findings from scanning electron microscope (SEM) analysis confirmed that the CD has a destructive effect on the mechanical characteristics of the soil–cement samples even in the long run. Correspondingly, delayed samples show lower secant modulus (1.81 times) rather than immediate compacted ones. Furthermore, higher CD yields mixtures with higher compression index and void ratio. Finally, laboratory test results are used to develop MDD and UCS regression models considering the CD parameter. The sensitivity analysis, based on regression models, shows that the MDD and UCS are noticeably influenced by cement content variations.

A Review on Correlations for Consolidation Characteristics of Various Soils

Settlement is the major problem that arises after the construction of a structure on a soil mass. Consolidation characteristics of soil such as coefficient of consolidation cv, compression index cc, recompression index cr, preconsolidation pressure σ′p play a major role in the settlement behavior of fine grained soil mass. cv represents the rate of consolidation of soil mass. cc and cr are essential in calculating settlement of normally and over consolidated clays respectively. σ′p is determined to find whether the clay is under, normally or over consolidated. These consolidation properties are obtained from graphical constructions after conducting several one dimensional consolidation-oedometer tests. Since this is time consuming, many correlations have been derived between consolidation properties and index properties of soil. Different researchers have used various soil parameters such as liquid limit (wL), plastic limit (wp), natural moisture content (wn), initial insitu void ratio (eo), dry unit weight (γd), plasticity index (Ip), void ratio at liquid limit (eL) etc., as correlative parameters for deriving the correlations. Hence, it is desirable to predict the value of cv, cc, cr and σ′p from the known correlations rather than conducting several tests, to ease the procedures.

Strength and dilatancy behaviors of deep sands in Shanghai with a focus on grain size and shape effect

With rapid development of infrastructures like tunnels and open excavations in Shanghai, investigations on deeper soils have become critically important. Most of the existing laboratory works were focused on the clayey strata up to Layer 6 in Shanghai, i.e. at depth of up to 40 m. In this paper, Layers 7, 9, and 11, which were mostly formed of sandy soils at depth of up to 150 m, were experimentally investigated with respect to physico-mechanical behaviors. The stress–strain behaviors were analyzed by the consolidated drained/undrained (CD/CU) triaxial tests under monotonic loading. One-dimensional (1D) oedometer tests were performed to investigate the consolidation properties of the sandy soils. Specimens were prepared at three different relative densities for each layer. Also, the micro-images and particle size analyzers were used to analyze the shape and size of the sand grains. The influences of grain size, density, and angularity on the stress–strain behaviors and compressibility were also studied. Compared to the other layers, Layer 11 had the smallest mean grain size (D50), highest compressibility, and lowest shear strength. In contrast, Layer 9 had the largest mean grain size, lowest compressibility, and highest shear strength. Layer 7 was of intermediate mean grain size, exhibiting more compressibility and less shear strength than that of Layer 9. Also, the critical state parameters and maximum dilatancy rate of different layers were discussed.