Application of Soil Stabilization Technique for Shoulder Construction in Sri Lanka

Park Ki Soo,Park Hee Mun 한국도로학회 2018 한국도로학회논문집 Vol.20 No.4

PURPOSES: The objective of this study is to evaluate the application of soil stabilization method for soft shoulder construction in the iRoad Project of Sri Lanka. METHODS: Firstly, the quantitative analysis of soil strength improvement due to soil stabilization was done for soil samples collected from iRoad construction sites. Two types of soils were selected from iRoad Project sites and prepared for soil stabilization testing by the Road Development Authority. Secondly, the appropriate stabilizer was selected at given soil type based on test results. Two different stabilizers, ST-1 and ST-2, produced in Korea were used for estimating soil strength improvements. Finally, the optimum stabilizer content was determined for improving shoulder performance. The uniaxial compressive strength (UCS) test was conducted to evaluate the strength of stabilized soil samples in accordance with ASTM D 1633. The use of bottom ash as a stabilizer produced from power plant in Sri Lanka was also reviewed in this task. RESULTS: It is found from the UCS testing that a 3% use of soil stabilizer can improve the strength up to 2~5 times in stabilized soft shoulder soils with respect to unstabilized soils. It is also observed from UCS testing that the ST-1 shows high strength improvement in 3% of stabilizer content but the strength improvement rate with increase of stabilizer content is relatively low compared with ST-2. The ST-2 shows a low UCS value at 3% of content but the UCS values increase significantly with increase of stabilizer content. When using the ST-2 as stabilizing agent, the 5% is recommended as minimum content based on UCS testing results. Based on the testing results for bottom ash replacement, the stabilized sample with bottom ash shows the low strength value. CONCLUSIONS: This paper is intended to check the feasibility for use the soil stabilization technique for shoulder construction in Sri Lanka. The use of soil stabilizer enables to improve the durability and strength in soft shoulder materials. When applying the bottom ash as a soil stabilizer, various testings should be conducted to satisfy the specification criteria.

Application of Soil Stabilization Technique for Shoulder Construction

Hee Mun Park,Su Hyung Lee,Pyeong Jun Yoo,Byung Sik Ohm,Ki Soo Park 한국도로학회 2018 한국도로학회 학술대회 발표논문 초록집 Vol.2018 No.05

In Sri Lanka, the shoulder in asphalt pavements has been constructed using the materials transported from borrow pit in the iRoad Project due to the low quality of in-situ soils. After excavating 150~200mm thick and 500mm wide shoulder area, the borrow pit materials are placed and compacted according to specifications. The excavated in-situ soils are dumped in designated location. It is estimated that this process of shoulder construction is not economical due to high material transportation cost and can also induce the environmental issues by disposal of in-situ soils. It can also cause distresses such as surface rutting and edge drop-off in soft shoulder section due to bearing capacity failure and off-tracking of vehicle. The heavy rainfall in Sri Lanka can induce severe erosion problem when using the soft shoulder. To improve the strength and durability of pavement shoulders in the iRoad Project, the soil stabilization will be a good alternative to solve the above mentioned problems. The use of in-situ soils with addition of soil stabilizer enables to reduce the construction cost of shoulder section and mitigate the environment issues. The objective of this task is to review the application of soil stabilization method for soft shoulder construction in the iRoad Project. Firstly, the quantitative analysis of soil strength improvement due to soil stabilization was done for soil samples collected from iRoad construction sites. Two types of soils were selected from iRoad Project sites and prepared for soil stabilization testing by the Road Development Authority. Secondly, the appropriate stabilizer was selected at given soil type based on test results. Three different stabilizers, ST-1, ST-2, and ST-3, produced in Korea were used for estimating soil strength improvements. Finally, the optimum stabilizer content was determined for improving shoulder performance. The uniaxial compressive strength (UCS) test was conducted to evaluate the strength of stabilized soil samples in accordance with ASTM D 1633. The use of bottom ash as a stabilizer produced from power plant in Sri Lanka was also reviewed in this task.

레드머드 중화 방법에 따른 토양 중 비소의 안정화 특성 평가

우지오,김은정,Woo, Jio,Kim, Eun Jung 한국지하수토양환경학회 2021 지하수토양환경 Vol.26 No.6

Since the amount of red mud, generated from aluminum smelting process as a by-product, has increased worldwide, the recycle and metal resource recovery from the red mud is becoming more important. In this study, in order to recycle the red mud as a soil stabilizer to remediate arsenic contaminated soils, neutralization of red mud was investigated. Red mud was neutralized by washing with distilled water and NaCl, CaCl₂, FeCl₃, and HCl solutions and heating at 200-800℃, and arsenic stabilization characteristics in soils were evaluated with the neutralized red mud. Although washing with distilled water was not effective in neutralizing red mud, the application of the washed red mud to soils lowered the soil pH compared to the application of untreated red mud. Among NaCl, CaCl₂, FeCl₃, and HCl solutions, washing with FeCl₃ showed the most effective in lowering pH of the red mud from pH 10.73 to pH 4.26. Application of the neutralized red mud in soils resulted in quite different arsenic stabilization efficiency depending on soil samples. In M1 soil, which showed relatively high arsenic stabilization efficiency by untreated red mud, the neutralization of red mud resulted in little effect on arsenic stabilization in soil. On the other hand, in M2 soil, which showed low arsenic stabilization efficiency by untreated red mud, the neutralization of red mud increased arsenic stabilization significantly. Soil characteristics such as clay minerals and pH buffering capacity seemed to affect reactions between red mud and soils, which resulted in different effects of the red mud application on soil pH and arsenic stabilization efficiencies.

도시 유역의 노출토양 실태와 표토보전 방안

박은진(Park Eun-Jin),강규이,이세라,좌승희 경기연구원 2008 경기개발연구원 기본연구 Vol.2008 No.11

This study aimed at investigating the impacts of soil exposure on stability of soil structure, soil erosion, and infiltration, and suggesting the management practices for soil conservation in urban watersheds. The study is composed of 1) literature review on the mechanism of soil stabilization and environmental impacts of soil exposure, 2) review on legislation system regarding soil conservation and management, 3) investigation of the area and aggregate stability of exposed soils in a case study area, 4) suggestion of management practices for soil conservation and improvement of soil processes. We defined "the exposed soils" as "soils that are exposed temporarily or permanently to disturbance without cover materials so that can be eroded" and examined the area and aggregate stabilities of exposed soils sampled from agricultural field (red peppers), riparian zones, roadsides, urban parks, and forests (oaks) in the Anyang Stream Watershed. The total area of exposed soils was 11.4% and the area of agricultural field soils were greatest. Soil organic matter content decreased in the order of forests, parks, agricultural fields, roadsides, and riparian zones. Aggregate stability decreased in the order of forests, parks, roadsides, riparian zones, and agricultural fields. The extent of exposure and disturbance were related to soil organic matter content and aggregate stability. Agricultural field soils contained greater organic matter content but their aggregate stability were lower comparing to roadsides or riparian soils. It was attributed to the more disturbance by agricultural activities. Grass cover on the soils of urban parks seemed to bring greater stability of soil aggregates comparing to other soil types. It seemed that grass can hold soil particles tightly and stabilize soil structure. In order to conserve soil structural stability and ecosystem, I suggest that the use of soil ecological index and soil conservation guideline for legislation system controlling construction works, soil bank system for recycling surface soils, recycling of wood materials as cover of soil surface, and soil education should be urgently conducted.

폐광산 토양개량‧복원사업 완료 농경지 안정화 효율 및 화학성 평가

고주인,박미선,박관인,백승한,고일하,Ju-In Ko,Mi-Sun Park,Gwan-In Park,Seung-Han Baek,Il-Ha Koh 한국지하수토양환경학회 2024 지하수토양환경 Vol.29 No.1

In Korea, the common remedial process for reclamation of agricultural soils nearby abandoned mines involves chemical soil stabilization followed by covering with clean soil. This study investigated the chemical properties of cover soils and the validity of HCl extraction method in assessing the degree of As and heavy metal stabilization in stabilized soils collected from 14 plots where mine reclamation had been completed. The results revealed there were no major differences in contaminants extraction rate between the stabilized soils and contaminated soils, suggesting HCl extraction procedure is a less feasible method to determine the efficiency of the stabilization. Soil quality indicators including OM, SiO₂, P₂O₅, etc. of the land-covering soils were generally lower than those of stabilized soils that used to be the cultivation layer before the stabilization. Nonetheless, the value of those indicators didn't meet the regulatry limits of agricultural soil. Therefore, future strategy for mine reclamation should concentrate not only on contaminant concentration but also on soil quality parameters for agricultural use of the reclaimed soil.

비소 오염토양의 안정화를 위한 나노 Fe°담지 바이오차 적용 연구

최유림 ( Yu-lim Choi ),( Ganesh Kumar Reddy Angaru ),안혜영 ( Hye-young Ahn ),박광진 ( Kwang-jin Park ),주완호 ( Wan-ho Joo ),양재규 ( Jae-kyu Yang ),장윤영 ( Yoon-young Chang ) 한국환경영향평가학회 2020 환경영향평가 Vol.29 No.5

본 연구에서는 전정가지 부산물과 one-pot 합성방법을 이용하여 철 나노입자가 담지된 바이오차인 INPBC(Iron Nano-Particles Impregnated BioChar)를 제조하고 비소 오염토양의 안정화제로써의 적용가능성을 평가하였다. INPBC는 전정가지 부산물과 Fe(III) 용액을 220°C에서 3시간 동안 수열반응하고 이후 N₂ 분위기에서 1시간 동안 소성하여 제조하였으며 FT-IR, XRD, BET, SEM을 이용하여 INPBC의 특성을 분석하였다. INPBC의 안정화 성능평가는 국내 E폐광산과 S폐광산의 인근 농경지에서 채취한 비소로 오염된 토양 Soil-E와 Soil-S를 채취하여 4주 동안의 배양실험을 실시하였다. 배양실험 후 토양중 비소의 안정화 정도를 알아보기 위해 TCLP와 SPLP 용출시험을 실시하였다. TCLP와 SPLP의 용출시험결과, INPBC의 적용 농도의 증가에 따라 토양 중 비소의 용출농도는 감소하여 안정화 효율이 높아지는 것을 확인할 수 있었으며, 특히 Soil-E의 경우 SPLP 용출액 중 비소의 농도는 먹는물 수질기준치 이하의 낮은 값을 나타내었다. 안정화 토양의 연속추출시험에서는 쉽게 용출되는 1단계 및 2단계의 분획비율이 감소되고 그 보다 용출이 어려운 3단계 및 4단계의 분획비율이 증가되는 것을 확인할 수 있었으며, 이러한 결과는 오염토양에 주입한 INPBC의 표면에 존재하는 철 나노입자로 인해 토양에서 용출된 비소가 sorption에 의해 안정화된 것으로 판단된다. 본 연구에서 나타난 INPBC의 비소 오염토양의 안정화 효과는 대규모 비소오염토양의 위해성 저감을 위한 안정화제로서 높은 적용 가능성을 보여 준다. In this study, nano Fe°-impregnated biochar (INPBC) was prepared using pruning residues and one-pot synthetic method and evaluated its performance as an amendment agent for the stabilization of arsenic-contaminated soil. For the preparation of INPBC, the mixture of pruning residue and Fe (III) solution was heated to 220°C for 3hr in a teflon-sealed autoclave followed by calcination at 600°C under N₂ atmosphere for 1hr. As-prepared INPBC was characterized using FT-IR, XRD, BET, SEM. For the stabilization test of as-prepared INPBC, As-contaminated soils (Soil-E and Soil-S) sampled from agricultural sites located respectively near E-abandoned mine and S-abandoned mine in South Korea were mixed with different of dosage of INPBC and cultivated for 4 weeks. After treatment, TCLP and SPLP tests were conducted to determine the stabilization efficiency of As in soil and showed that the stabilization efficiency was increased with increasing the INPBC dosage and the concentration of As in SPLP extractant of Soil-E was lower than the drinking water standard level of Ministry of Environment of South Korea. The sequential fractionation of As in the stabilized soils indicated that the fractions of As in the 1st and 2nd stages that correspond liable and known as bioavailable fraction were decreased and the fractions of As in 3rd and 4th stages that correspond relatively non-liable fraction were increased. Such a stabilization of As shows that the abundant nano Fe° on the surface of INPBC mixed with As-contaminated soils played the co-precipitation of As leaching from soil by surface complexation with iron. The results of this study may imply that INPBC as a promising amendments for the stabilization of As-contaminated soil play an important role.

접착성 식생기반재의 침식저항능력 평가

성시융(Si-Yung Seong),신은철(Eun-Cheol Shin) 한국지반신소재학회 2015 한국지반신소재학회 논문집 Vol.14 No.2

기존의 비탈면녹화공법인 식생기반재취부공법은 결합력의 부족이나 건조화, 유기물의 부족 등의 문제점들을 보이고 있다. 특히 비산이 심한 지역의 비탈면은 식생피복율이 현저히 떨어지고 시간이 경과함에 고사율이 증가되어 피복율이 더 저하되고 또다시 침식 및 비산이 증가하는 악순환이 이루어지고 있는 상황이다. 따라서 본 연구에서는 침식이나 비산에 저항하기 위해 친환경 토양안정재를 적용하고, 적정 배합비 결정을 위해 장기침수시험과 유수저항시험을 실시하였다. 친환경토양안정재와 기존의 녹화토기반재를 활용한 장기침수시험결과, 토양안정재의 혼합율 0%는 30시간, 2%는 40일 후 100% 붕괴가 발생되었으며, 4% 이상의 혼합비에서는 실험종료시까지 시료의 원형이 그대로 남아 있어 2% 이상의 토양안정재가 극한 조건에서도 형상을 유지하는데 영향을 줄 수 있는 혼합비임을 확인하였다. 또한, 식생기반재의 구조적 안정성을 평가하기 위해 인공강우시험을 40, 45, 55° 경사비탈면에 대해 실시하였으며, 토양안정재의 혼합비 0, 4, 8%에 대해 유수저항시험을 실시하고 침식저항 능력을 평가하였다. 실험결과, 토양안정재의 혼합에 따라 유실률이 급격히 감소하는 경향을 보이는 등 비산을 방지하거나 우수에 의한 침식에 저항하기 위해 적용한 친환경 토양안정재가 큰 유실감소효과를 거둘 수 있을 것으로 판단된다. This paper describes vegetation based soil-media hydroseeding measures that have been previously applied as slope revegetation methods show problems such as insufficient binding force, drying, and insufficient organic matter. In particular, in the case of slope faces in regions where scattering is severe, a vicious circle exists in which remarkably low vegetation cover rates and increases in withering rates over time lead to further decreases in vegetation cover rates, which lead to further increases in erosion and scattering. Therefore, in the present study, environment friendly soil stabilizers were applied for resistance against erosion or scattering and engineering evaluations such as long-term immersion tests and flow resistance tests were conducted to determine appropriate mixing ratios. According to the results of long-term immersion tests utilizing environment friendly soil stabilizers and existing greening soil based materials, 100% collapse occurred at 30 hours and 40 days in the case of soil stabilizer mixing ratios of 0% and 2%, respectively. While the original form of the samples remained intact until the experiment was completed in the case of mixing ratios exceeding 4% indicating that 2% or higher soil stabilizer mixing ratios could affect the maintenance of forms even under extreme conditions. In addition, artificial rainfall tests were conducted on 40, 45, and 55 degree slope faces to evaluate the structural stability of vegetation based materials. Flow resistance tests were conducted on soil stabilizer mixing ratios of 0, 4, 8% to evaluate erosion resistance capability. Based on the results of the tests, environment friendly soil stabilizers applied for prevention of scattering or resistance against erosion by rainwater are considered to provide large effects to reduce losses and loss rates showed a tendency of decreasing rapidly when soil stabilizers were mixed.

Stabilization of expansive soil using industrial wastes

Mohanty, Soumendra K.,Pradhan, Pradip K.,Mohanty, Chitta R. Techno-Press 2017 Geomechanics & engineering Vol.12 No.1

Swelling and shrinkage characteristics of expansive fine grained soil cause volumetric changes followed by distress and damage to the structures. Soil stabilization can be explained as the alteration of the soil properties by chemical, mechanical or any other means in order to enhance the engineering properties of the soil. Utilization of industrial wastes in soil stabilization is cost effective and environment friendly. This paper presents an experimental study on stabilization of expansive soil using industrial wastes, viz. fly ash and dolochar. The paper includes the evaluation of engineering properties like unconfined compressive strength and California bearing ratio (CBR) of expansive soil collected from Balasore district of Odisha stabilized with fly ash and dolochar in different proportions and to predict the influence of these additives on engineering properties and strength characteristics of expansive soil. Both fly ash and dolochar were found to increase the CBR and decrease many index properties such as liquid limit, plastic limit, plasticity index, swelling index and UCS, thus enhancing the strength parameters of expansive soil.

Stability and Micro-mechanisms of Lignin-improved Soil in a Drying-wetting Environment

Gaoqiang Wang,Xianghui Kong,Yanhao Zhang,Quanman Zhao,Xiao Feng 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.8

To evaluate the long-term service performance of subgrade with high-liquid-limit soil improved by lignin, a drying-wetting cycle test was carried out for the improved soil with 3% lignin content, and comparison was made with quicklime-improved soil with the same properties in terms of pH, unconfined compressive strength (UCS), appearance, and volume stability. Using a scanning electron microscope (SEM), the microscopic characteristics of the lignin-improved soil were analyzed qualitatively and quantitatively. By analyzing the evolution law of the soil microstructure and pores under the action of drying-wetting cycles, the strength degradation mechanism of the improved soil was discussed at the microscopic level. The test results showed that the soil pH value of the lignin-improved soil was more beneficial to the ecological environment compared with that of the quicklime-improved soil. Furthermore, the stability of the lignin-improved soil was better than that of the quicklime-improved soil due to strength loss and increased volume expansion rate caused by the drying-wetting cycles. In terms of the microstructure, the cementing materials enhanced the agglomeration of the soil by wrapping grains and filling pores. Under the action of drying and wetting, the number of pores inside the soil increased, and the soil structure loosened. Under drying and wetting conditions, the strength degradation of the lignin-improved soil was the result of the interaction of pore development and cementing materials dissolution.

Mg-Fe 이중층수산화물로 제조한 분말상과 입상 안정화제의비소 오염토양 안정화 기작

김선희,김경태,오유나,한이경,이민희 한국지하수토양환경학회 2022 지하수토양환경 Vol.27 No.4

The magnesium and iron-based layered double hydroxide (Mg-Fe LDH) was synthesized by the co-precipitation processand the bead type LDH (BLDH, 5~6 mm in diameter) was manufactured by using the Mg-Fe LDH and the starch as abinder. To evaluate the feasibility of the BLDH as the As stabilizer in the soil, various experiments were performed andthe As stabilization efficiency of the BLDH was compared to that of powdered type LDH (PLDH, <149 μm in diameter). For the As sorption batch experiment, the As sorption efficiency of both of the PLDH and the BLDH showed higher than99%. For the stabilization experiment with soil, the As extraction reducing efficiency of the PLDH was higher than 87%,and for the BLDH, it was higher than 80%, suggesting that the BLDH has similar the feasibility of As stabilization for thecontaminated soil, compared to the PLDH. From the continuous column experiments, when more than 7% BLDH wasadded into the soil, the As stabilization efficiency of the column maintained at over 91% for 7 pore volume flushing(simulating about 21 months of rainfall) and slowly decreased down to 64% after that time (to 36 months) under the nonequilibriumconditions. Results suggested that more than 7% of BLDH added in As-contaminated soil could be enough tostabilize As in soil for a long time. The main As fixation mechanisms on the LDH were also identified through the X-rayfluorescence (XRF), the X-ray diffraction (XRD), and the Fourier transform infrared (FT-IR) analyses. Results showedthat the LDH has enough of an external surface adsorption capacity and an anion exchange capability at the interlayerspaces. Results of SEM/EDS and BET analyses also supported that the Mg-Fe LDH used in this study has sufficientporous structures and outer surfaces to fix the As. The reduction of carbonate (CO32-) and sulfate (SO42-) anions in theLDH after the reaction between As and the LDH was observed through the FT-IR, the XRF, and the XRD analyses,suggesting that the exchange of some of these anions with the arsenate (H2AsO4- or HAsO42-) occurs at the LDHinterlayers during the stabilization process in soil.