Investigation and Treatment Analysis of Barikan Landslide

In last several years periodic reports indicating damages toward resident;s homes due to ground movements in Barikan region, 120km far from tehran, have been issued. The earth movements are demonstrated by tension cracks and scraps on ground surfaces and walls of in site homes and gardens. Since the slow and continuous earth movements were observed in the site, a course of site investigation consisted of the monitoring of surface and deep earth movements has been considered to study the affecting factors and the extent of of landslide. In addition to ground movement measurements, by using the geotechnical properties of different soil layers, stability analysis of the soil mass was performed. Results showed that the village would be stable at static conditions in all relative groundwater levels. However, in case of earthquake with value of horizontal acceleration equal to 0.14g, analyses indicated total instability of the site. It seems that the movements, which apparently widen the cracks and damage the houses and walls of the gardens, are due to the mild in site earthquakes or accelerations of the farther occurred earthquakes of the area, which by reducing the F.S. of the slope, increase the severity of movements rate in the village. In this paper the results of conducted researches, as well as possible remedial solutions for ground movements, with regard to known effective factors of landslide, are presented

Geotechnical behaviour of the carbonate sand-granulated tire mixture

149-155Carbonate sand-tire mixture is used in this research as a soil improvement method to address the environmental problems regarding the accumulation of scrap tires in coastal areas. The stress-strain behaviour, internal friction angle, and the particle breakage of the carbonate sand-tire mixture are studied, and the results are compared to that of pure carbonate sand. The results revealed that the addition of the granulated tires to the carbonate sand changed its behaviour. The addition of granulated tires resulted in a decrease of both the friction angle and the quantity of particle breakage

Effect of MSW leachate on soil consistency under influence of electrochemical forces induced by soil particles

Investigations on the effect of leachate from municipal solid waste on the soils in landfill sites usually focus on the effect of leachate compounds on the engineering properties of the soil. Leachate chemical composition and its effect on the consistency of soil are important factors for designing liner systems. Soil samples from the bottom of the Esfahan, Iran, landfill were collected. Leachate samples were collected within the a landfill and a composting factory leachate lagoon. Effects the leachates on cation exchange capacity, electrical conductivity, pH, and consistency of the soil samples were investigated. The chemical property of leachate showed that leachate from the compost factory was contaminated by higher concentrations of heavy metals (Cu, Zn, Pb, Cd, Ni, and Hg); higher concentrations of Na+,Ca+2, Mg+2, and K+; and higher EC; and were more acidic than the landfill leachate. Liquid limits and plastic limits of the soil were higher from the effect of the compost factory leachate in comparison with the values for landfill leachate

Chemico-geomechanical sensitivities of tropical peat to pore fluid pH related to controlling electrokinetic environment

Peat is an accumulation of partially decayed vegetation with high noncrystalline content (humus), which is formed in wetland systems. Chemico-geomechanical sensitivities of a fibrous (very slightly decomposed) and a sapric (highly decomposed) peat to peat-water pH gradients in terms of resulting effects on cation exchange capacity (CEC), zeta potential (ζ), particle density, liquid limit (LL), particle size distribution, dry density–moisture content relationship, permeability, and undrained shear strength (Su) have been investigated. The specimens were treated for a 20-day period under acidic and basic conditions. It was found that in both fibrous and sapric peat, the CEC and ζ decreased; the LL, permeability, Su, and the optimum moisture content (OMC) increased, and the grain size distribution became skewed toward larger particles because of acidic conditions, while basic conditions had a contrary effect. The sensitivities of the fibrous peat to peat-water pH gradients were not of such intensity as were observed in the sapric peat because of the naturally inherited peat structure, degree of decomposition, ion change capacity, particle size, surface charges, and specific surface area. Our results are important, in that they confirm the link between the degree of peat humification and the chemico-geomechanical sensitivities of the peat to peat-water pH gradients

Physicochemical sensitivities of tropical peat to electrokinetic environment

Tropical peat is unconsolidated superficial deposits with high non-crystalline colloid (humus) content, constituting the subsurface of wetland systems. Laboratory experiments were carried out on a very slightly decomposed fibric and a highly decomposed amorphous, undisturbed tropical peat soils, to determine the physicochemical effects on the peats due to electrokinetic (EK) treatment in terms of mechanisms and resulting effects in the presence of peat water. The different specimens were treated for 3, 6, 12, and 20-day periods. A constant electrical potential of 40 V was applied across the specimens. The untreated and treated specimens were tested for liquid limit (LL), undrained shear strength (Su), water content (WC), zeta potential (¥æ), pH, and cation exchange capacity (CEC). The peat water flew from anode to cathode because of the negative charges on the humus. In the vicinity of the anode, the CEC and ¥æ of the specimens decreased, and the Su and LL of the specimens increased because of the acidic conditions, while alkaline conditions at the cathode had an opposite effect. The sensitivity of the amorphous peat to the EK environment was higher than the sensitivity of the fibric peat to the EK environment because of larger quantities of the colloids and quality of the charges. The acid/base distributions in EK soil processing influenced the soil surface charges, which were fully pH-dependent, resulting in the variations of the CEC and ¥æ. The ¥æ variations caused thinning and expanding of the diffuse double layer around the humus particles, and were linked to the flocculation and dispersion of the particles, and subsequently affected the LL and Su of the specimens. The study was found its significance in that it confirmed the relationship between the degree of peat decomposition and the peat sensitivity to the EK treatment

Geotechnical behaviour of the carbonate sand-granulated tire mixture

Carbonate sand-tire mixture is used in this research as a soil improvement method to address the environmental problems regarding the accumulation of scrap tires in coastal areas. The stress-strain behaviour, internal friction angle, and the particle breakage of the carbonate sand-tire mixture are studied, and the results are compared to that of pure carbonate sand. The results revealed that the addition of the granulated tires to the carbonate sand changed its behaviour. The addition of granulated tires resulted in a decrease of both the friction angle and the quantity of particle breakage

Clayey soil stabilization using alkali-activated volcanic ash and slag

Lime and Portland cement are the most widely used binders in soil stabilization projects. However, due to the high carbon emission in cement production, research on soil stabilization by the use of more environmentally-friendly binders with lower carbon footprint has attracted much attention in recent years. This research investigated the potential of using alkali-activated ground granulated blast furnace slag (GGBS) and volcanic ash (VA) as green binders in clayey soil stabilization projects, which has not been studied before. The effects of different combinations of VA with GGBS, various liquid/solid ratios, different curing conditions, and different curing periods (i.e. 7 d, 28 d and 90 d) were investigated. Compressive strength and durability of specimens against wet-dry and freeze-thaw cycles were then studied through the use of mechanical and microstructural tests. The results demonstrated that the coexistence of GGBS and VA in geopolymerization process was more effective due to the synergic formation of N-A-S-H and C-(A)-S-H gels. Moreover, although VA needs heat curing to become activated and develop strength, its partial replacement with GGBS made the binder suitable for application at ambient temperature and resulted in a remarkably superior resistance against wet-dry and freeze-thaw cycles. The carbon embodied of the mixtures was also evaluated, and the results confirmed the low carbon footprints of the alkali-activated mixtures. Finally, it was concluded that the alkali-activated GGBS/VA could be promisingly used in clayey soil stabilization projects instead of conventional binders

Electroosmotic phenomena in organic soils

Organic soils or peat represent an accumulation of disintegrated plant remains which have been preserved under condition of incomplete aeration and high water content. In order to develop a fundamental understanding of electroosmotic phenomena in peat, initially microelectrophoresis studies were carried out to conceptualize the electrokinetic phenomena. Then electroosmosis experiments were conducted on rigid cube samples containing 0.0001 M NaCl-water saturated peat. The open-anode and open-cathode systems were employed to the soil samples. Distilled Water (DW) were used as anolyte and catholyte. The experiments were carried out via applications of diffrent DC electrical potentials. The results of microelectrophoresis study showed changes of zeta potential due to the effect of HCl and NaOH. The correlations between zeta potential and pH were found. The negative charge of peat is high pH dependent and the surface charge was dropped to zero at pH around 3. The high degree of decomposition resulted in the higher zeta potential in peat. It was also experimentally found that the electroosmotic flow in peat is feasible. The direction of electroosmotic flows were from the anode to cathode

Compressive strength of sandy soils stabilized with alkali-activated volcanic ash and slag

In recent years, compared with the traditional portland cement, environmentally friendly geopolymers have gained more attention as construction materials. This paper considered volcanic ash (VA) and ground granulated blast furnace slag (GGBFS) in different percentages (0%, 3%, 7%, and 10%) as a replacement for the conventionally used portland cement to stabilize sandy soils. NaOH and Na2SiO3 in different concentrations (4, 8, and 12 M) and alkali to binder ratios (1, 1.5, 2, and 3) were used as alkali activator solutions to build new geopolymers. Samples were cured at both ambient and oven temperatures and for 1, 7, and 28 days. Unconfined compressive strength (UCS) of samples then was evaluated. Two predictive approaches, artificial neural network (ANN) modeling and the evolutionary polynomial regression technique (EPR), were applied to model UCS of geopolymerized sand samples. Regarding the high value of the coefficient of determination of the proposed ANN, 97%, and acceptable prediction errors, RMS error of 0.0439 and MAE of 0.0336, an 8-5-10-1 ANN was introduced as a more accurate tool for the prediction of UCS. Next, three-dimensional parametrical studies investigated the effects of simultaneous changes in alkali solution, binder, and curing condition parameters on UCS values of geopolymerized samples. Sensitivity analysis based on the cosine amplitude method introduced the Si/Al ratio as the parameter most affecting and VA content as the parameter least affecting the compressive strength of samples. Results were analyzed further using pH and electrical conductivity tests and interpreted based on microstructural investigations using scanning electron microscopy (SEM) images and X-ray diffraction analysis

Effects of protein-based biopolymer on geotechnical properties of salt-affected sandy soil

Salt-affected soils cannot meet the needs of engineering projects due to their deficiency in providing desirable geotechnical properties. Cement stabilization is widely used to improve the engineering properties of salt-affected soils, but cement has many backward effects, especially on the environment, limiting its application as a binder. This study evaluates the potential effects of salt on protein-based biopolymer treated sand. The influence of salt content, biopolymer content, and curing time on the strength and stiffness development of salt-affected sand was explored with unconfined compressive strength (UCS) testing. The UCS results showed that an increase in casein biopolymer content led to an increase in the unconfined compressive strength and stiffness; however, the addition of salt had a reverse effect on UCS results. By adding 2% casein solution, the compressive strength reached 1021.34 kPa, which is significantly greater than that of untreated soil with a value close to zero. When the salt content rose from 0.5 to 10% (for 2% casein content), a substantial strength loss (more than 48%) was observed in the UCS value from 978 to 501 kPa. This might be due to the salt existence in soil which adversely affected the biopolymer connections by blocking the bonds and bridges with soil particles. This adverse effect was gradually mitigated by the biopolymer increment until adding 3.5% sodium caseinate, then a higher percentage of the biopolymer was involved in further enhancement of compressive strength. Microscopic observation revealed that sodium caseinate acted as a binding agent between soil particles, while salt disrupted the sodium caseinate performance. To evaluate the physical properties of the sandy soil, permeability and wind tunnel tests were conducted. The inclusion of sodium caseinate as a protein-based biopolymer resulted in lowering the hydraulic conductivity and increasing the erosion resistance of salt-affected sand. Curing time had positive effects on strength development, increasing the erosion resistance, and reducing the permeability. Overall, sodium caseinate could adequately improve the engineering properties of salt-affected sand