지반보강용 실리카졸-시멘트 그라우팅재의 특성에 관한 연구

Abstract

약액을 이용한 연약지반처리공법은 지하수의 수위저하 및 유출을 막기 위한 차수목적과 지반의 지지력을 유지하거나 향상시키기 위한 보강목적으로서 타 공법에 비해서 도심지 지하철 굴착공, 산악터널 굴착공과 같이 좁은 공간에서도 쉽게 적용이 가능하고, 시공 장비가 간편하며, 시공목적을 신속히 발휘할 수 있기 때문에 선진 외국의 경우 그 활용성이 매우 높고 기술발전 수준도 상당히 높은 단계에 와 있다. 현재까지 물유리(3호)(이하 물유리)를 사용한 기존의 물유리계 약액주입공법은 주입 후 시간경과에 따라 지하수에 의해 알칼리용탈이 진행되어 결국에는 내구성이 약한 문제점 있다. 따라서 이에 대한 대안으로서 내구성이 우수하고 환경오염의 가능성이 적은 새로운 주입재 및 그의 주입공법에 대한 개발이 요구되어 물유리계 약액주입공법의 단점을 보완하기 위해 개발된 공법이 알칼리성 실리카졸 약액주입공법이다. 알칼리성 실리카졸은 직접산화법으로 제조된 제품으로서 기존에 현장에서 제작하여 사용하던 산성 실리카졸과 비교시 실리카졸의 안정성이 높고 고농도 및 보관성이 양호한 특징이 있다. 따라서 본 논문에서는 최근 개발된 알칼리성 실리카졸 주입재의 주입효과 평가를 위해서 주입재 자체에 대한 강도, 내화학성 및 환경영향성에 대한 시험을 수행하였다. 현재까지 차수 및 지반안정을 위해 시행되어 온 물유리를 사용한 기존의 물유리계 주입재와 비교·분석 하였으며 주입재의 겔타임을 조정하기 위해 급결, 완결로 구분해서 실험하여 주입재별 시공목적에 따른 겔타임을 도출하였다. 알칼리성 실리카졸 주입재의 특성 및 주입효과에 대한 연구결과, 주입재 상호간을 비교할 수 있는 일축압축강도 특성을 통하여 알칼리성 실리카졸 주입재가 상당한 고강도를 나타냄으로서 고강도, 고침투성을 발휘할 수 있는 재료로 사용될 수 있음을 확인하였다. 환경영향평가시험은 호모겔에서 중금속 용탈시험을 수행하였다. 용탈시험결과 규제기준을 만족하고 있어 중금속 용출에 대해 안정성을 가지고 있다고 판단된다. 전자현미경 촬영 결과 실리카졸 그라우팅재의 표면 및 내부조직이 물유리보다 치밀함을 확인할 수 있었다. 투수시험 결과 실리카졸이 물유리와 비교시 투수계수가 낮게 나타나 차수성을 요구하는 현장에 적용이 가능하다고 판단된다. 휨강도시험결과 알칼리성 실리카졸은 최종 28일강도의 경우 물유리 그라우팅재에 비해 3배 이상의 차이를 보이고 있다. 현장시험으로서는 새만금 2호 방조제 끝막이구간에 돌망태사석과 피복석 등으로 시공된 바닥보호공으로 침투되는 해수에 의한 파이핑 현상을 방지하기 위하여 바닥보호공에 복합그라우팅으로 차수공사에서 시험시공 하였으며 시험결과 시공 전 바닥보호공층은 투수계수가 1.01 × 10-2cm/sec의 사석층으로 소량의 준설해사가 일부 충전되어 있는 상태였으며 알칼리성 실리카졸을 사용한 복합그라우팅 시공 후 투수시험결과 7.30 × 10-6cm/sec로 나타나 내구성 있는 차수벽조성에 효과적인 것으로 판단된다. 위의 연구결과를 종합해 보면 강도시험, 내화학성시험, 환경영향성평가시험 등을 통해 알칼리성 실리카졸 주입재를 사용한 경우가 물유리를 사용한 경우보다 우수한 것으로 나타났으며, 내구성 있는 차수벽조성에는 물유리계 주입재 보다는 알칼리성 실리카졸을 적용해야 될 것으로 판단된다. | Compared to other methods, the soft ground treatment method using liquid chemicals can be applied in the narrow space such as excavation work for subway of the downtown area and mountain tunnel excavation work for the purpose of preventing for lowering and outflow of a ground water level and reinforcing maintenance and improvement of bearing power of ground, and because construction equipment is convenient and the purpose of construction can be shown quickly, its usability is very high and the technology development level is also significantly high in case of advanced foreign countries. Until now, the existing water glass-based chemical grouting method using water glass(No.3)(hereinafter, called water glass) has a weak durability problem in the end by progression of alkaline leaching by underground water according to the elapsed time after grouting. Accordingly, the development on new grouting material and its grouting method that durability is superior and has less possibility of environmental pollution as an alternative on this was required, so that the alkaline silicasol chemical grouting method was developed to complement disadvantages of the water glass-based liquid chemical grouting method. The alkaline silicasol is a product made by a direct oxidation method and has characteristics that have high silicasol stability as well as high concentration and good storage properties, compared to acidic silicasol that was made in the existing field. Accordingly, this thesis has performed tests on strength, chemical resistance and environmental effects about grouting material itself for assessment of grouting effects of recently developed alkaline silicasol-based grouting material. This thesis has compared and analyzed existing water glass-based grouting material that was being executed for waterproofing and ground stability until present, and deduced gel-time according to the construction purpose by grouting material by dividing it into rapid setting or slow setting in order to adjust gel-tine of grouting material. As a research result on properties and grouting effects of alkaline silicasol grouting material, the alkaline silicasol grouting material showed significantly high-strength through uniaxial compressive strength properties capable of comparing grouting materials with each other, so it was confirmed that it can be used as materials that can show high-strength and high-permeability. In case of the environmental effect assessment test, heavy metal leaching tests were carried out in homo-gel. As a result of leaching tests, it is judged that as it satisfies the regulation criteria, it has stability on heavy metal leaching. As a result of electron microscope photographing, it could be confirmed that the surface and internal structure of silicasol grouting material is more dense than water glass. As a result of permeability tests, it is judged that as the permeability coefficient of silicasol appeared to be lower than water glass, its application is possible in the field requiring waterproofing. As a result of bending strength test results, alkaline silicasol is showing a difference of more than 3 times in case of the final 28th day's strength compared to water glass grouting material. In order to prevent piping phenomena by seawater being permeated into bed pitching constructed with wire cylinder's sand and stone and riprap protection, etc. in the final closing section of a tide embankment Saemangeum no.2 as a field test, waterproofing works were constructed in riprap protection by complex grouting. As a test result, the riprap protection layer before construction was a sand and stone layer with the permeability coefficient of 1.01 × 10-2cm/sec and was partially filled with a small amount of dredged sea sand, and as a result of the permeability test after construction of complex grouting using alkaline silicasol, it appeared as 7.30 × 10-6cm/sec, so it is judged that it is effective in formation of waterproofing walls. When generalizing the above research results, the case using alkaline silicasol grouting material through strength tests, chemical resistance tests and environmental effect assessment tests, etc. appeared to superior to the case using water glass, so it is judged that alkaline silicasol should be applied to formation of durable waterproofing walls, rather than water glass-based grouting material.; Compared to other methods, the soft ground treatment method using liquid chemicals can be applied in the narrow space such as excavation work for subway of the downtown area and mountain tunnel excavation work for the purpose of preventing for lowering and outflow of a ground water level and reinforcing maintenance and improvement of bearing power of ground, and because construction equipment is convenient and the purpose of construction can be shown quickly, its usability is very high and the technology development level is also significantly high in case of advanced foreign countries. Until now, the existing water glass-based chemical grouting method using water glass(No.3)(hereinafter, called water glass) has a weak durability problem in the end by progression of alkaline leaching by underground water according to the elapsed time after grouting. Accordingly, the development on new grouting material and its grouting method that durability is superior and has less possibility of environmental pollution as an alternative on this was required, so that the alkaline silicasol chemical grouting method was developed to complement disadvantages of the water glass-based liquid chemical grouting method. The alkaline silicasol is a product made by a direct oxidation method and has characteristics that have high silicasol stability as well as high concentration and good storage properties, compared to acidic silicasol that was made in the existing field. Accordingly, this thesis has performed tests on strength, chemical resistance and environmental effects about grouting material itself for assessment of grouting effects of recently developed alkaline silicasol-based grouting material. This thesis has compared and analyzed existing water glass-based grouting material that was being executed for waterproofing and ground stability until present, and deduced gel-time according to the construction purpose by grouting material by dividing it into rapid setting or slow setting in order to adjust gel-tine of grouting material. As a research result on properties and grouting effects of alkaline silicasol grouting material, the alkaline silicasol grouting material showed significantly high-strength through uniaxial compressive strength properties capable of comparing grouting materials with each other, so it was confirmed that it can be used as materials that can show high-strength and high-permeability. In case of the environmental effect assessment test, heavy metal leaching tests were carried out in homo-gel. As a result of leaching tests, it is judged that as it satisfies the regulation criteria, it has stability on heavy metal leaching. As a result of electron microscope photographing, it could be confirmed that the surface and internal structure of silicasol grouting material is more dense than water glass. As a result of permeability tests, it is judged that as the permeability coefficient of silicasol appeared to be lower than water glass, its application is possible in the field requiring waterproofing. As a result of bending strength test results, alkaline silicasol is showing a difference of more than 3 times in case of the final 28th day's strength compared to water glass grouting material. In order to prevent piping phenomena by seawater being permeated into bed pitching constructed with wire cylinder's sand and stone and riprap protection, etc. in the final closing section of a tide embankment Saemangeum no.2 as a field test, waterproofing works were constructed in riprap protection by complex grouting. As a test result, the riprap protection layer before construction was a sand and stone layer with the permeability coefficient of 1.01 × 10-2cm/sec and was partially filled with a small amount of dredged sea sand, and as a result of the permeability test after construction of complex grouting using alkaline silicasol, it appeared as 7.30 × 10-6cm/sec, so it is judged that it is effective in formation of waterproofing walls. When generalizing the above research results, the case using alkaline silicasol grouting material through strength tests, chemical resistance tests and environmental effect assessment tests, etc. appeared to superior to the case using water glass, so it is judged that alkaline silicasol should be applied to formation of durable waterproofing walls, rather than water glass-based grouting material.