Coefficient Of Volume Compressibility Research Articles

Analysis of the Consolidation Properties of Soil in the Mucherbari Regulator in Sunamganj

Analysis of the Consolidation Properties of Soil in the Mucherbari Regulator in Sunamganj

The Effect of Oil Pollution on the Engineering Properties of Construction Soils in Some Selected Oil Region of Nigeria: A Case Study of Four Oil Towns in Rivers and Delta States

The nature of subgrade as well as basic information of soils for construction purposes is important for engineers, especially civil engineers and the general public. The primary aim of this research work is therefore to access the effect of oil spillage on the engineering properties of soils around the oil producing states of Nigeria. Four communities in two state of the Niger- Delta region of Nigeria were selected for investigation. These communities include Alesa (as sample A) and Aleto (as sample B) in Rivers state and Elume (as sample C) and Mereje (as sample D) in Delta state of the Niger- Delta region of Nigeria. Soil samples from these communities were collected at the subgrade depth of the oil spilled soils and was later subjected to laboratory examination. Important soil properties that were evaluated through laboratory investigation include soil shear strength test using triaxial test where the shear strength parameters were determined to enable evaluation of soil bearing capacity using Terzaghi’s equations. Others include soil strength (CBR) test, soil permeability test, and soil classification test as well as soil compressibility tests or one dimensional consolidation test. The results show that the oil pollution/ spillage have affected the engineering properties of construction soils in the four towns investigated to some degrees. The California Bearing Ratio (CBR) value of the subgrade, the Coefficient of Volume Compressibility,Mv, the Safe Bearing Capacity and the Coefficient of Permeability, K of the investigated soil , all fall below the accepted standard limit for soils to be used for construction purposes. This result will hopefully add to the existing knowledge as well as equipping the government and other relevant agencies for policy and regulatory development for the oil and gas, and construction industries for the sustenance of economic development in Nigeria. Therefore, before any meaningful civil engineering construction works can be done in these communities, the soils within the area will have to be subjected to series of engineering soil tests so as to equip the government and other interesting stakeholders with the requisite knowledge on how to apply appropriate soil remediation and soil stabilization techniques.

Semi‐analytical solution for double‐layered elliptical cylindrical foundation model improved by prefabricated vertical drains

AbstractThis work proposes a semi‐analytical solution for a double‐layered elliptical cylindrical soft foundation improved by prefabricated vertical drains. The governing equations, continuity conditions are boundary conditions in the elliptical cylindrical system are introduced first. The Laplace transform is employed to convert the time variable t in partial differential equations into the Laplace complex argument s. Based on the boundary condition and continuity condition, the solution in the frequency domain is derived. By using Abate's fixed Euler Algorithm, the solutions in the time domain are obtained. A finite element analysis is performed to demonstrate the accuracy of the proposed solution. Then, parametric studies reveal that soil permeability and soil compressibility have great influences on the second layer of soil in the elliptical cylindrical system, but relatively small effects on the first layer. Neglecting differences in the hydraulic conductivity and the coefficient of volume compressibility of multi‐layered soil in the elliptical cylindrical system could not predict the excess pore pressure in the second layer correctly.

Application of Geoinformatics in Civil Engineering Design and Construction: A Case Study of Ile Oluji, SW Nigeria

Subsoil engineering site condition and modeling of engineering parameters has been carried out in Ile Oluji, Ondo State, Southwestern Nigeria, using geotechnical investigation, geophysical method, borehole logging, groundwater level measurement, and laboratory studies. Findings revealed that the soils are clayey of low-high plasticity/compressibility, with AASHTO classification of A-7-6. Based on average values of cohesion (48.4 KN/m2), angle of friction (17.4°), unconfined compressive strength (186.8 KN/m2), coefficient of permeability (2.13E-06 cm/s), activity (0.48), soaked CBR (7 %), MDD/OMC (1980 kg/m3/14.8 %), plasticity index (20.2 %), group index (6 %), compression index (0.0443), coefficient of volume compressibility (0.2041 m2/KN), depth to basement rock (22.2 m), static water levels 5.5 m (in well) and 21.8 m (in borehole), the soil is unsuitable for highway subgrade, subbase, and base courses. Thus, if it is expedient to use it as subgrade soil, the minimum recommended thickness is 241 – 513 mm (avg. 395 mm). The average allowable bearing capacity of the soil for square and round foundations are 268.4 KN/m2 and 267.95 KN/m2 respectively, with average total settlement of 18.3 mm for structural pressure of 100 KN/m2. For embankment, the suitability index (1.21) of the soil suggests a fair/expanding not collapsible construction material. The rock units in the area have high compressive/shear strength, modulus of elasticity, high crushing strength, low deformability; and presumable bearing capacity of 8, 000 – 10, 000 KPa when fresh, and 5000 – 7000 KPa when partly or slightly weathered. Thus are valuable as foundation constructions, aggregate in pavement, building stone, and armourstones. The correlation coefficient of the parameters are: MDD/PI vs. CBR (0.0043), LL vs. coefficient of consolidation (0.0608), PI vs. undrained shear strength/effective overburden (0.2706), PI vs. angle of shearing (0.0117), dry density vs. angle of shearing (0.0058), suitability index vs. CBRs (0.3644), clay contents vs. PI (0.1355).

Improvement of Clay Soil Using a Plaster Mortar Additive

This study examines possibility of improving clayey soils in the Handere Formation exposed in the vicinity of Adana (S. Turkey), one of the largest cities in southern Turkey. The Handere Formation, from where the samples for this study are taken, is stratigraphically at the upper most part of the marine sediments of the Adana Basin. The unit is located at the northern part of Adana city. The samples were examined in the geotechnical laboratory to determine the effect of plaster mortar (Master Cast) on the geotechnical properties of the soil and its ability to improve the soil. shear box, consolidation, unconfined compressive strength tests were applied on the samples. It has been shown that the master cast used can improve soil properties geometrically and can be used as a soil stabilizer. The plasticity values of the soils were reduced by master cast addition. Besides, it was determined that the highest maximum dry unit weight and the lowest optimum moisture content were obtained by 15% master cast addition. The soil strength properties were reached to the top values in case of 15% master cast added into the mixtures. Besides, it is determined that the coefficient of volume compressibility (Mv) and the pre-consolidation pressure values are ideal when the master cast ratio in the mixtures are 10% and 5% respectively.

Experimental Approach for Assessing Dissipated Excess Pore Pressure Induced Settlement

Upon dynamic loading, saturated soil loses its strength and behaves differently with respect to the excess pore pressure variation resulting in volumetric-induced settlements. Traditionally, these settlements have been evaluated using standard charts based on one soil type and its relative density (RD). To assess these settlements, this study established a unique experimental methodology based on two laboratory tests: triaxial simple shear and piezoelectric ring actuator technique. Fifty-seven tests were performed on Ottawa F65 sand under strain-controlled cyclic and post-cyclic conditions. A chart was generated, revealing a relationship between the dissipated energy from cyclic loading and volumetric strain (v), based on the shear wave velocity as a controlling factor. This study was compared with previous studies to verify the compatibility of the proposed approach. Another novelty was revealed by studying v variation with the dissipated pressure. This variation is presented in a post-seismic chart, in which deformations are tracked based on the initial soil state and maximum excess pore pressure generation ratio (Rumax). For each RD, the soil is divided between liquefied and non-liquefied states according to a specific Rumax (Rumax-trigger point). The calculation of the volume compressibility coefficient is proven to serve as a liquefaction-triggering criterion identifying the liquefied state.

Semi-analytical solution for two-dimensional electro-osmotic consolidation of double-layered soil

This study proposed a semi-analytical solution for 2D electro-osmotic consolidation of double-layered soil. The method of Laplace transform is employed to derive the solution in the frequency domain. Then the numerical approach of inverse Laplace transform is used to obtain the explicit solution in the time domain. A finite element simulation is conducted to validate the proposed solution's accuracy. The verification example shows excellent agreement between the two methods. Based on the parametric study, it is found that the value of soil parameters in the second layer has significant influences on the behaviour of electro-osmotic consolidation. The larger the electro-osmosis coefficient in the second layer, the smaller the excess pore pressure at a given time. Additionally, a higher coefficient of volume compressibility in the second layer results in higher excess pore pressure. Compared with the 1D case, the distribution of excess pore pressure at the steady state is non-linear with depth in the 2D electro-osmotic consolidation, rather than a linear distribution. Furthermore, the dissipation rate and steady-state excess pore pressure could be underestimated if the electro-osmotic consolidation is modelled as a 1D case.

On the anomalous high-pressure phase transition of inderite, MgB3O3(OH)5·5H2O

The high-pressure behaviour of inderite [ideally MgB3O3(OH)5·5H2O, Sp. Gr. P21/c with a = 6.8105 (2), b = 13.0955 (5), c = 12.0144 (6) Å, β = 104.556 (4)° at room conditions], has been studied by in-situ single-crystal synchrotron X-ray diffraction up to 17 GPa, in order to explore its stability field at high-pressure, the anisotropy of its compressional behaviour and the deformation mechanisms at the atomic scale. Between 6.45 (5) and 6.94 (5) GPa, inderite experiences a first-order phase transition (from P21/c to P21/n, with a = 13.4308 (7), b = 11.9970 (5), c = 10.4466 (8) Å, and β = 100.030 (6)° at 6.45 (5) GPa, ΔV⁓ 7%), reconstructive in character, to the inderite-II polymorph, whose structure was successfully solved and refined. The isothermal bulk modulus (KV0 = β−1P0,T0, where βP0,T0 is the volume compressibility coefficient) of inderite was found to be KV0 = 26.5 (7) GPa, whereas in inderite-II the KV0 value increases to 41(5) GPa. The compressional anisotropy of the two polymorphs is drastically different, being the ratio between the principal components of the unit-strain ellipsoid: ε1:ε2:ε3 ⁓ 4.3:2.7:1 for the low-P polymorph and ε1:ε2:ε3 ⁓3.0:2.7:1 for the high-pressure one. The deformation mechanisms at the atomic scale, in inderite and inderite-II, are here described. The pressure at which the phase transition of inderite occurs represents an anomalous and (so far) unique case among the hydrated polyionic borates.

An Evaluation of a Marginal Land’s Geological Engineering Properties in Borikiri Sandfill, Port Harcourt Nigeria

Aim: The aim of this study was to assess the geological engineering properties of a marginal land in Borikiri Sandfill, Port Harcourt, Nigeria, using both field and laboratory investigations.
 Study Design: The study design involved the drilling of 4 boreholes and standard penetration tests to determine the soil profile and index properties such as particle size analysis, atterberg limits, and moisture content. Consolidation and triaxial tests were also performed to determine the values of the coefficients of permeability (k), volume compressibility (Mv), and consolidation (Cv).
 Place and Duration of Study: The Study was conducted in Borikiri Sandfill, Port Harcourt between February and May 2020.
 Methods: This study's methodology included field research, laboratory analysis, and testing. Drilling and conventional penetration tests were used to assess the soil profile. Laboratory tests such as particle size analysis, atterberg limits, and moisture content were used to determine the index characteristics. The values of permeability (k), volume compressibility (Mv), and consolidation (Cv) were also determined using triaxial and consolidation tests.
 Results: The results of the study showed that the soil profile consists of five stratigraphic sequences, with a top organic silty layer followed by a sandy layer, a dark plastic layer, a dark silty clayey sand, and a well-graded sand. The clays had an average Liquid limit (LL) of 45% and a Plastic Limit (PL) value of 23%. The values of k, Mv, and Cv were determined to be 2.1 x 10-7 m/s, 1.8 x 10-4–2.5 x 10-4 m2/MN, and 3.8 m2/yr, respectively. The average bearing capacity values at 2.5 m and 4.5 m depths were determined to be 186.39 kPa and 278.71 kPa, respectively. Settlement values were calculated empirically for immediate and consolidation settlement, with immediate settlement being high at 25.85 mm and consolidated settlement being 7.53mm. T50 and T90 values were also determined to be 1.32 and 4.52 years, respectively.
 Conclusion: It is recommended that a shallow foundation, down to the first layer, can be used for any light construction on the marginal land in Borikiri Sandfill, Port Harcourt, Nigeria. The values of k, Mv, and Cv also indicate that the soil is relatively compressible, which should be taken into account in any design or construction activities.

Engineering Geological Properties of Subsurface Soils for Foundation Purposes in Parts of Bayelsa State, Niger Delta

The geotechnical properties of soil samples obtained from eight (8) boreholes from some parts of Bayelsa State were determined to assess their suitability as foundation materials. The geotechnical characteristics of the soils were determined from the laboratory and field works. The Atterberg limit results reveal that the liquid limit ranges from 46.5% to 98.3%, the plastic limit ranges from 23.5% to 56.3% while the plasticity Index values range from 17.1% to 51.3%. The clays are highly plastic (CH) in the USCS designation. The natural moisture content ranges from 35.9% to 91.3%, the moisture content is relatively high, this could be attributed to the wet season period of sampling. The particle size analysis disclosed that the cohesionless samples are predominantly fine to medium and medium dense sands. The triaxial test results shows that values of Cohesion (C) ranges between 16 – 40KN/m2 and the friction angle (ϕ) ranges between 3 – 6o. The result of the undrained shear strength of the clay ranges between 20Kpa and 24Kpa. The coefficient of consolidation (Cv) of the clay soil samples varies between 1.13 m2/yr and 2.89 m2/yr, the coefficient of volume compressibility, (Mv) for these same materials varies between 0.215 m2/MN and 6.338 m2/MN. Generally, indicating clay layers of high to very high compressibility. The calculated values for ultimate bearing capacity (qu) and allowable bearing capacity (qa) varies between 100.29KN/m2 to 151.49 KN/m2 and 33.42 KN/m2 to 50.50 KN/m2 respectively. The analyses showed that the values of ultimate bearing capacity increases with depth. The calculated settlement ranges between 69mm to 653mm with the thickness of clay of 7.5m and 30.0m respectively. Raft foundation is best suited for these weak, soft foundation materials for light structural loads but for heavy structural load, a pile foundation is recommended.

Mechanical and Electronic Properties of a Carbon-Composite 3D Nanomaterial with an Island-Type Topology

An atomistic model of a carbon-composite 3D nanomaterial with an island-type topology based on fullerene and graphene fragments as well as chiral/achiral single-walled carbon nanotubes (SWCNTs) with a subnanometer diameter is constructed. The island type refers to the presence of inhomogeneously distributed local regions with increased density of the nanomaterial in the structure of the composite. The effect of the concentration of nanotubes in the composite on the volume compressibility and electronic properties is investigated. It is found that an increase in the mass fraction of SWCNTs in the composite leads to a decrease in the coefficient of volume compressibility and, at the same time, improvement in the conductive properties. Classical molecular dynamics and the density functional based tight binding (DFTB) method with the use of dispersive energy correction are used for the physically correct description of individual fragments of the composite which are not covalently bound.

GEOMETRY ASSESSMENT ON THE SLOPE STABILITY OF MANYAR POND

Lateritic soil was treated with 0%, 4%, 8%, 12%, and 16% Rice Husk Ash (RHA) by dry soil weight to determine its consolidation properties. Test carried out include particle size distribution, specific gravity, compaction test with varying compactive efforts (British Standard Light (BSL), West African Standard (WAS) as well as British Standard Heavy (BSH)) and consolidation test. Samples for consolidation test were compacted and then cured for 7, 28 and 56 days; then subjected to one dimensional consolidation testing to observe the influence of curing period and compactive effort on its consolidation characteristics. Index tests showed improved geotechnical properties. The Maximum Dry Density (MDD) for BSL compaction decreased with a rise in RHA content from 1.72 to 1.42 Mg/m3 while optimum moisture content (OMC) increased from 16.5% to 27.3% with rise in RHA doses from 0% up to 16%. Similar trend was observed for WAS and BSH energies. Pre-consolidation pressure rise with increment in RHA content and also with increase in both compactive efforts and curing period with few exceptions. At 12% RHA content, Pre-consolidation pressure increased from 65 to 66.5 kN/m2 at 7 days and 56 days respectively. Increase in RHA content caused a decrease in Compression Index and Swelling Index. Compression Index also decreased with increase in both compactive efforts and curing period. There was no observed trend in the Swell Index with curing period. As the compactive efforts increased, the swell index decreased. The RHA reduced the Coefficient of Volume Compressibility (Mv) and the Coefficient of Consolidation (Cc). Curing period and compactive effort have no effect on Mv and Cc. Based on the results obtained, curing period at least 28 days using up to 12% RHA compacted at energy level of BSH improved the properties of the treated soil and can be used for geotechnical engineering applications like embankment or rural roads.

Spatial variation of permeability and consolidation behaviors of soil using ordinary kriging method

The present study is aimed at finding out spatial distribution of permeability characteristic of soil using ordinary kriging method at any location using the data from a few boreholes at NIT (National Institute of Technology) Patna Bihta campus. Kriging is also popularly known as BLUE (i. e. Best Linear Unbiased Estimator) which can be used to interpolate the data obtained from a few locations to get an estimate of any parameter at other locations throughout the study area. In the present work, soil samples collected from eight boreholes have been tested to obtain various geotechnical properties including liquid limit (LL), plastic limit (PL), plasticity index (IP), coefficient of volume compressibility (mv) etc. These values have been used as inputs in an Ordinary Kriging model to calculate coefficient of consolidation (Cv) and coefficient of permeability (k) throughout the NIT Patna, Bihta campus and build contour plots of (Cv) and (k) over the NIT Patna campus to show their spatial variation. The novelty of the current work lies in the first time proposed method for developing the spatial distribution of(Cv) and(k). Markov correlation matrix has been used to develop the correlation behavior of the parameters considering different values of correlation length. In the present study, it is found that the coefficient of consolidation Cv of soil ranges 10−8 (m2/sec). The Kriged values of k are in the range of 10−11 to 10−10 (m/s). Finally, semi-variogram have been shown to display the auto-correlation of the measured data points and cross-validation of data set which establish that the Kriged data are reasonably correlated. Also, various error estimators such as Mean Error, Root Mean Square Error, Average Standard Error, Root Mean Square Standard Error, Mean Standard Error have been calculated using the Kriged data points over the entire area and, it is found that the error level in the predicted Kriged data are reasonably small.

General analytical solutions for one-dimensional large strain consolidation of soft soils under electro-osmosis–surcharge preloading

In this study, the governing equation for one-dimensional large strain consolidation of soft soils under electro-osmosis–surcharge preloading is derived with some assumptions, and the general analytical solution is proposed for the first time by using the methods of algebraic transformation and separation variable. The expressions for the specific analytical solutions under several common cases in foundation treatment are developed. Besides, the correctness of the proposed analytical solutions is verified by comparing them with the existing analytical solutions and finite difference solution. Finally, based on the proposed analytical solutions, the effects of effective voltage Vm, the ratio of electro-osmosis (EO) conductivity to hydraulic conductivity ke/kv and volume compressibility coefficient mv1 on the consolidation behaviors are analyzed. It is found that the increase of Vm increases the absolute values of excess pore water pressure (EPWP) and hence the settlement increases. Furthermore, the increasing ratio of ke/kv leads to larger absolute values of EPWP generated in the soil, resulting in an increase of settlement. The consolidation degree Us defined by settlement based on small strain and large strain models decreases with the increase of mv1, and both the differences of Us and settlement between the two consolidation theories increase with the increase of mv1. In conclusion, the proposed analytical solution is simple in form and practical, which can be adopted to analyze the one-dimensional large strain consolidation behaviors under electro-osmosis–surcharge preloading.

Coupled model for consolidation and organic contaminant transport in GMB/CCL composite liner under non-isothermal distribution condition

The transport behavior of organic contaminants in the composite liner is affected by both consolidation and thermal diffusion. However, research on the coupled theory is still limited. In this study, the governing equations for consolidation and organic contaminant transport in GMB/CCL (geomembrane and compacted clay liner) composite liner are developed under non-isothermal distribution condition, and the corresponding coupled model is established. Meanwhile, the numerical method is adopted to obtain the finite difference solutions for consolidation and organic contaminant transport, respectively. Besides, the correctness of the proposed coupled model is validated by comparing the existing analytical solution with the theoretical model. Finally, the effects of different factors on the transport behaviors are discussed, in which trichloroethylene is chosen as the research object. It is found that the influence of non-isothermal distribution on the transport process is amplified when consolidation is neglected rather than considered. Moreover, the effects of consolidation on the transport behaviors are more remarkable under the non-isothermal distribution condition than under the isothermal distribution condition, where the volume compressibility coefficient plays a vital role. Overall, the coupled influences of multi-factors such as thermal diffusion and consolidation should be considered simultaneously to properly evaluate the transport characteristics of organic contaminants.

Eco-friendly stabilization of highway lateritic soil with cow bone powder admixed lime and plastic granules reinforcement

Modernization, industrialization and rapid changes in the modern lifestyle have resulted in massive waste materials in the environment. Scientists are continuously evolving innovative ways for efficient reuse/recycling and the safe disposal of waste materials. This study explores potential waste materials reuse in additive stabilization of a fair to poor highway lateritic soil (clay with low plasticity/silty clay) as a sub-base material and the impact of such additives in reducing the lime content during soil stabilization treatment. Soil samples obtained from road construction burrow pit in Ado-Ekiti, south-west, Nigeria were classified as CL group (clay with low plasticity), according to the Unified Soil Classification System (USCS) and A-6 material (silty clay) which is fairly poor highway material. Hydrated lime, Cow bone and plastic wastes were also locally sourced. Geotechnical tests (Compaction, Unconfined Compressive Strength test, direct shear and consolidation test) were carried out on the control and stabilized samples according to BS 1990. The results of the Unconfined Compressive Strength tests revealed that the 90 % lateritic soil +10 % lime and a combination of 6 % lime +7 % cow bone powder +1 % plastic waste (6 % L +7 % CBP + 1.0 %PP) mixes produced the best result for the lime stabilized and waste-lime stabilized soil samples, respectively. The direct shear tests, indicated a reduction in the soil’s cohesion (c) from 38 kN/m 2 to 28 kN/m 2 and an improvement in the angle of internal friction ( ϕ ) from 29º to 45º for the optimum waste-lime mix. 10 % lime (L 10 ) sample recorded comparatively lower c and ϕ values of 33 kN/m 2 and 41º, respectively. The mix (6 % L +7 % CBP + 1.0 % PP) had improved the unsoaked and soaked CBR of 61.7 % and 37.6 %, respectively compared to the lime stabilized soil which recorded lower values of 57.8 % and 31.3 %, respectively. The permeability of the soil was reduced from 3.22e-03 cm/s to 9.12e-04 cm/s on the application of 10 % lime however the waste-lime optimal mix produced a lower value of 5.26e-04 cm/s. The results of the consolidation tests also revealed that the 6 % L +7 % CBP +1.0 % PP sample had a lower coefficient of volume compressibility (Mv) of 1.065e-04 m 2 /kN than the untreated samples which is 1.365e-04 m 2 /kN implying the stabilized mix is less susceptible to compressibility than the untreated samples. The durability results revealed that the sample recorded a strength of 201.7 kPa after being subjected to 3 wet-dry (w-d) cycles for 6 % L +7 % CBP +1.0 % PP sample, while the 10 % lime stabilized soil was found to have a strength of 148.5 kPa strength. Based on the findings, it can be concluded that the 6 % L +7 % CBP +1.0 % PP mix performed better than the 10 % lime stabilized mix with the waste materials substituting for 4 % of the lime and producing better results in terms of suitability as a highway sub-base material. • The partial replacement of lime improved weak highway lateritic soils. • Waste materials (cow bone powder and plastic granules) were suitably reused. • Near-zero emissions processing of stabilization additives was achieved. • Cleaner and energy-saving methods were employed for the disposal of waste. • Reduced weather sensitivity and compressibility were achieved for the soil mixture.

The investigation of geochemical and geomechanical properties in surface paste disposal by pilot‑scale tests

ABSTRACT Today, seepage control in tailings dams has become an important problem due to the increased production in mining sites. Although very techniques have been developed to solve this problem, research in this field continues. The reason for this is that there is an ongoing search for a one hundred percent successful method to prevent seepage. In this study, the geochemical and geomechanical properties of paste material stored by the surface paste disposal (SPD) method were investigated by pilot field tests. To determine the effects of cement and pozzolanic materials on the geochemical and geomechanical properties of the paste, 2 different pilot-scale storage designs were observed for about 1 year, with no additives (reference) and binder added to some layers (cement and fly ash). Based on the data derived from the former laboratory investigations and with no additives and with a few layers of cement and fly ash, the two different designs were applied on a pilot scale near the existing tailings dam of a currently active mining enterprise. These designs were observed in inland conditions for about 1 year to determine the effects of seasonal changes on the material. The seepage analysis, surface crack densities, microstructural properties, consolidation, and cohesion values of these designs, which are directly exposed to atmospheric effects, were determined during the study period. According to the results obtained, the use of cement improved the volume compressibility coefficient of the material by approximately 25% compared to the reference design. However, the use of fly ash alongside cement improved the volume compressibility coefficient by about 75%. In conclusion, the use of cement made the material more resistant to external factors, and the usability of fly ash, which was used at a 50% replacement ratio with cement to bring down the cost, for long-time storage in the industry was demonstrated within the scope of the study.

General analytical solutions for one‐dimensional nonlinear consolidation of saturated clay under non‐isothermal distribution condition

AbstractThe fluctuation of temperature leads to the changes of physical‐mechanical properties of clayey soils. In some practical projects such as landfills, the compacted clay liner is usually subjected to a non‐isothermal distribution state. For one‐dimensional nonlinear consolidation process of saturated clay under non‐isothermal distribution condition, the general analytical solutions considering time‐dependent loading are derived for the first time, where the methods of algebraic transformation and separation variable are used. Moreover, two forms of boundary conditions are included according to engineering practice. Referring to the proposed general analytical solutions, the expressions for the analytical solutions under instantaneous loading pattern and single‐stage linear loading pattern are developed. Besides, the correctness of the presented analytical solutions is validated by comparing with the existing analytical solutions and finite difference solutions. Based on the proposed analytical solutions, the influence of temperature gradient, final loading and loading time on the consolidation behaviors is analyzed. It is found that the increase in temperature gradient accelerates the consolidation rate, and the average volume compressibility coefficient decreases by 65.4% when final loading increases from 50 to 500 kPa. In conclusion, the analytical solutions proposed in this study are more comprehensive and can be applied in different engineering cases.

CONSOLIDATION CHARACTERISTICS OF LATERITIC SOIL TREATED WITH RICE HUSK ASH

Lateritic soil was treated with 0, 4, 8, 12 and 16% rice husk ash (RHA) by dry weight of soil to determine its consolidation properties. Test carried out include; particle size distribution, specific gravity, compaction test with varying compactive efforts (British Standard Light (BSL), West African Standard (WAS) as well as British Standard Heavy (BSH)) and consolidation test. Samples for consolidation test were compacted and then cured for 7, 28 and 56 days; then subjected to one dimensional consolidation testing to observe the influence of curing period and compactive effort on its consolidation characteristics. Index tests showed improved geotechnical properties. The maximum dry density (MDD) for BSL compaction decreased with a rise in RHA content from 1.72 to 1.42 Mg/m3 while optimum moisture content (OMC) increased from 16.5 to 27.3% with rise in RHA doses from 0 up to 16%. Similar trend was observed for WAS and BSH energies. The Pre-consolidation pressure rise with increment in RHA content and also with increase in both compactive efforts and curing period with few exceptions. At 12% RHA content, the Pre-consolidation pressure increased from 65 to 66.5kN/m2 at 7 days and 56 days respectively. Increase in RHA content caused a decrease in Compression Index (Cc) and Swelling Index (Cs). Compression Index also decreased with increase in both compactive efforts and curing period. There was no observed trend in the Swell Index with curing period. As the compactive efforts increased, the swell index decreased. The RHA reduced the Coefficient of Volume Compressibility (Mv) and the Coefficient of Consolidation (Cc). Curing period and compactive effort have no effect on Mv and Cc. Based on the results obtained, curing period of atleast 28 days using up to 12% RHA compacted at energy level of BSH improved the properties of the treated soil and can be use for geotechnical engineering applications like embankment or rural roads.

High-pressure behaviour and atomic-scale deformation mechanisms in inyoite, CaB3O3(OH)5·4H2O

The compressional behaviour of inyoite, ideally CaB3O3(OH)5·4H2O, has been studied by an in-situ high-pressure single-crystal X-ray experiment, at the ESRF large-scale facility, up to 19.80(5) GPa. Inyoite undergoes a first-order phase transition to inyoite-II, bracketed between 8.25(5) and 8.86(5) GPa, with a large volume discontinuity (ΔV ⁓ 7.5%). The structure of the high-pressure polymorph has not been solved due to a significant decrease in the number of Bragg reflections. The isothermal bulk modulus (KV0 = β−1P0,T0, where βP0,T0 is the volume compressibility coefficient) of inyoite was found to be KV0 = 26.9(8) GPa, whereas in inyoite-II, the KV0 value increases to 52(5) GPa. The increase of the bulk modulus is paired with a sharp decrease of the anisotropy of compressibility, as shown by the magnitude of the Eulerian finite unit-strain ellipsoid with: ε1:ε2:ε3 = 3.5:2.1:1 in inyoite and ε1:ε2:ε3 = 1.5:1.1:1 in inyoite-II. The P-induced deformation mechanisms controlling, at the atomic scale, the bulk compression of inyoite are here described on the basis of a series of structure refinements.