scholarly journals Effect of zeolite utilization on volume change and strength properties of expansive soil as landfill barrier

2017 ◽  
Vol 54 (9) ◽  
pp. 1320-1330 ◽  
Author(s):  
Şerife Öncü ◽  
Huriye Bilsel
Keyword(s):  
Hydraulic Conductivity ◽  
Volume Change ◽  
Expansive Soil ◽  
Confining Pressure ◽  
Good Alternative ◽  
Strength Properties ◽  
Landfill Liner ◽  
Swell Potential ◽  
Compressibility Characteristics ◽  
Natural Reserves

A sand–Na–bentonite mixture is widely used as engineering barrier material, which usually possesses hydraulic conductivity below the regulatory limit (10−7 cm/s). However, in some areas natural Na–bentonite is not readily available; instead, an abundantly prevailing local expansive soil can be an alternative. This study assesses the suitability of a local expansive soil mixed with zeolite, easily obtained from natural reserves in Turkey, proposed to be used as a landfill liner in a semi-arid climate. The choice of zeolite is due to its already well-understood high adsorption capacity for heavy metals as well as its pozzolanicity. The volume change, strength, and hydraulic conductivity characteristics were studied with respect to durability through ageing. When an expansive soil to zeolite ratio of 0.5 was used, the results indicated improved properties with curing. Swell potential was observed to decrease by 85% within a 90 day curing period, while a 30%–34% reduction was noted in shrinkage and compressibility characteristics. The hydraulic conductivity was observed to remain below the regulatory limit under all confining pressure ranges studied, provided the curing time was at least 90 days. Moreover, the mixture attained improved strength characteristics with time, and proved to be sustainable over the period studied. Therefore, it was concluded that expansive soil mixed with zeolite could be a good alternative to sand–Na-bentonite, mainly in developing areas of growing population and environmental degradation.

scholarly journals Characterization of Sand and Zeolite Stabilized Expansive Soil as Landfill Liner Material under Environmental and Climatic Effects

2020 ◽  
Vol 195 ◽  
pp. 03034
Author(s):  
Şerife Öncü ◽  
Huriye Bilsel
Keyword(s):  
Environmental Changes ◽  
Expansive Soil ◽  
Climatic Effects ◽  
Liner Material ◽  
Landfill Liner ◽  
Durability Analysis ◽  
Swell Potential ◽  
Alternative Material ◽  
Experimental Findings

This study focusses on the assessment of sand stabilized expansive soil as possible landfill liner materials to be utilized in a semi-arid area. Zeolite was also used as an alternative material to sand, mixing it with the expansive soil forming a stable structure with improved properties. Durability analysis of expansive soil-sand (NS) and expansive soil-zeolite (NZ) mixtures was studied to investigate the climatic and environmental effects on the sustainability of the proposed materials. The climatic effect is studied in terms of cyclic swell-shrinking and the environmental effect, mainly due to temperature elevations in the landfills, is studied in swell-compressibility tests. Cyclic swell-shrink tests and temperature variations (25°C, 40°C and 60°C) were applied on 28-day cured samples of NS and NZ mixtures in order to evaluate their resistance to climatic and environmental changes. Experimental findings showed that swelling potential and axial shrinkage were reduced with the increasing of wetting-drying cycles of both NS and NZ samples. The biggest variation of swell potential and axial shrinkage occurred at 7th cycle for NS (28-d) and 8th cycle for NZ (28-d) soil specimens. Primary swell percentage decreased with the increase of temperature in NS group, whereas, a reverse behavior was observed in NZ group.

scholarly journals Shrink-swell potential, hydraulic conductivity and geotechnical properties of clay materials for landfill liner construction

2015 ◽  
Vol 29 (3) ◽  
pp. 365-375 ◽  
Author(s):  
Marcin K. Widomski ◽  
Witold Stępniewski ◽  
Rainer Horn ◽  
Andrzej Bieganowski ◽  
Lucjan Gazda ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Particle Density ◽  
Total Porosity ◽  
Saturated Hydraulic Conductivity ◽  
Landfill Liner ◽  
Angle Of Internal Friction ◽  
Drying And Rewetting ◽  
Swell Potential ◽  
Basic Characteristics ◽  
Clay Materials

Abstract This paper presents studies concerning the applicability of two clay materials for the construction of a sustainable landfill liner. The studies consisted in determination of basic characteristics of the materials, eg particle size distribution, bulk density, particle density, total porosity, pore size, mineralogy, specific surface area, nanoparticle size, and Atterberg limits, as well as measurements of their geotechnical and hydraulic parameters, such as in situ saturated hydraulic conductivity, modules of primary and secondary compression, cohesion, and angle of internal friction. Furthermore, the effects of compaction performed by the Proctor method at various water contents on swelling and shrinkage characteristics and saturated hydraulic conductivity were investigated in order to determine the compliance with the national requirements for selection of material for landfill liner construction. The determined characteristics and geotechnical parameters of the tested clay materials allowed qualifying them as suitable for municipal landfill construction. The shrinkage potential of the tested clays observed was rated as moderate to very high. The cyclic drying and rewetting of the clay materials performed resulted in a significant increase in saturated hydraulic conductivity. Thus, the clay sealing layers, as part of a multilayer liner, should be very carefully operated, preventing the drying out of the clay sealing and assuring the possibility of its constant saturation.

Research on Hydraulic Conductivity of Coarse Sandstone under Triaxial Compression

2011 ◽  
Vol 94-96 ◽  
pp. 1146-1151 ◽  
Author(s):  
Guan Rong ◽  
Xiao Jiang Wang
Keyword(s):  
Hydraulic Conductivity ◽  
Circumferential Strain ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Test Results ◽  
Stress Strain ◽  
Deformation And Failure ◽  
Maximum Value ◽  
Strain Process ◽  
Peak Value

Permeability test for complete stress-strain process of coarse sandstone were carried out in triaxial test instrument. On the basis of test results, the influence of confining pressure and strain on the hydraulic conductivity was discussed. It is shown that in the complete stress-strain process, hydraulic conductivity changes in the law that presents the same character with the curve of stress-strain. The hydraulic conductivity reduces slightly with the increase of deviatoric stress in the stage of micro fracture compressing and elastic; In the elastoplastic stage, along with the expansion of new fractures, the hydraulic conductivity increases slowly at first and then reaches sharply to the maximum value after peak point; In the post-peak stage, the fracture which controls the hydraulic conductivity of coarse sandstone is compressed because of the confining pressure and the hydraulic conductivity decreases. During the process of deformation and failure, the hydraulic conductivity is more sensitive to the change of circumferential strain. With the increase of confining pressure, the increased value from initial to peak value and the decreased value from peak to residual value decreases.

scholarly journals Fault geometry and earthquake mechanics

1994 ◽  
Vol 37 (6) ◽  
Author(s):  
D. J. Andrews
Keyword(s):  
Stress Concentration ◽  
Volume Change ◽  
Triple Junction ◽  
Stress Drop ◽  
Single Point ◽  
Stress Singularity ◽  
Confining Pressure ◽  
Fault System ◽  
Earthquake Mechanics ◽  
Fresh Fracture

Earthquake mechanics may be determined by the geometry of a fault system. Slip on a fractal branching fault surface can explain: 1) regeneration of stress irregularities in an earthquake; 2) the concentration of stress drop in an earthquake into asperities; 3) starting and stopping of earthquake slip at fault junctions, and 4) self-similar scaling of earthquakes. Slip at fault junctions provides a natural realization of barrier and asperity models without appealing to variations of fault strength. Fault systems are observed to have a branching fractal structure, and slip may occur at many fault junctions in an earthquake. Consider the mechanics of slip at one fault junction. In order to avoid a stress singularity of order 1/r, an intersection of faults must be a triple junction and the Burgers vectors on the three fault segments at the junction must sum to zero. In other words, to lowest order the deformation consists of rigid block displacement, which ensures that the local stress due to the dislocations is zero. The elastic dislocation solution, however, ignores the fact that the configuration of the blocks changes at the scale of the displacement. A volume change occurs at the junction; either a void opens or intense local deformation is required to avoid material overlap. The volume change is proportional to the product of the slip increment and the total slip since the formation of the junction. Energy absorbed at the junction, equal to confining pressure times the volume change, is not large enongh to prevent slip at a new junction. The ratio of energy absorbed at a new junction to elastic energy released in an earthquake is no larger than P/µ where P is confining pressure and µ is the shear modulus. At a depth of 10 km this dimensionless ratio has th value P/µ= 0.01. As slip accumulates at a fault junction in a number of earthquakes, the fault segments are displaced such that they no longer meet at a single point. For this reason the volume increment for a given slip increment becomes larger. A juction with past accumulated slip ??0 is a strong barrier to earthquakes with maximum slip um < 2 (P/µ) u0 = u0/50. As slip continues to occur elsewhere in the fault system, a stress concentration will grow at the old junction. A fresh fracture may occur in the stress concentration, establishing a new triple junction, and allowing continuity of slip in the fault system. The fresh fracture could provide the instability needed to explain earthquakes. Perhaps a small fraction (on the order of P/µ) of the surface that slips in any earthquake is fresh fracture. Stress drop occurs only on this small fraction of the rupture surface, the asperities. Strain change in the asperities is on the order of P/µ. Therefore this model predicts average strais change in an earthquake to be on the order of (P/µ)2 = 0.0001, as is observed.

scholarly journals Experimental Study on Dynamic Resilient Modulus of Lime-Treated Expansive Soil

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Zheng Lu ◽  
Yang Zhao ◽  
Shaohua Xian ◽  
Hailin Yao
Keyword(s):  
Moisture Content ◽  
Environmental Changes ◽  
Resilient Modulus ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
The Stability ◽  
Compaction Degree

Dynamic resilient modulus is the design index of highway subgrade design code in China, which is significantly affected by the traffic loads and environmental changes. In this study, dynamic triaxial tests were conducted to investigate the influence of moisture content, compaction degree, cyclic deviator stress, and confining pressure on lime-treated expansive soil. The suitability of UT-Austin model to lime-treated expansive soils was verified. The results indicate that the dynamic resilient modulus of lime-treated expansive soils increases nonlinearly with the increase of compaction degree, while decreases nonlinearly with the increase of dynamic stress level. The dynamic resilient modulus decreases linearly with the increase of moisture content and increases linearly with the increase of confining pressure. Moreover, the moisture content has a more significant effect on the dynamic resilient modulus of lime-treated expansive soil. Therefore, it is necessary to ensure the stability of soil humidity state and its excellent mechanical properties under long-term cyclic loading for the course of subgrade filling and service. Finally, the calculated results of the UT-Austin model for dynamic resilient modulus show a good agreement with the test results.

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