• Geomechanics and Engineering
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• 제34권2호
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• pp.125-138
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• 2023

To improve the understanding of infiltration characteristic of modified slurry and the support efficiency of filter cake in silty sand strata, the slurry infiltration (SI) and filter cake formation (FCF) were investigated in a laboratory apparatus. The water discharge and the excess pore pressure at different depths of silty sand strata were measured during SI. The relationship between permeability coefficient/thickness ratio of filter cake (k_c/ΔL) and effective slurry pressure conversion rate of filter cake (η) were analyzed. Moreover, the SI and FCF process as well as the modification mechanism of CMC (carboxymethyl cellulose) were clarified. The experimental results indicate the formation of only external filter cake in the silty sand strata. The slurry particles obtain thicker water membrane after being modified by CMC, which blocks partial water path in filter cake and decreases the water discharge significantly. The silty sand excavated from tunnel face also contributes to the water discharge reduction. The k_c of the external filter cake ranges from 3.83×10^-8 cm/s to 7.44×10^-8 cm/s. The η of the external filter cake is over 96%, which decreases with increasing k_c/ΔL. A silty sand content within 10% is suggested during construction to ensure the uniformity of the filter cake.

• Advances in nano research
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• 제9권1호
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• pp.59-67
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• 2020

Filter cake formation during rotary drilling operation is an unavoidable scenario, hence there is need for constant improvement in the approaches used in monitoring the cake thickness growth in order to prevent drill-string sticking. This study proposes an improved model that predicts the growth of mud cake thickness overtime with the consideration of the addition of nanoparticles in the formulated drilling fluid system. Ferric oxide, titanium dioxide and copper oxide nanoparticles were used in varying amounts (2 g, 4 g and 6 g), and filtration data were obtained from the HPHT filtration test. The filter cakes formed were further analyzed with scanning electron microscope to obtain the morphological characteristics. The data obtained was used to validate the new filtrate loss model. This model specifically presents the concept of time variation in filter cake formation as against the previous works of constant and definite time. Regression coefficient which is a statistical measure was used to validate the new model and the predicted results were compared with the API model. The new model showed R² values of 99.9%, and the predictions from the proposed filtration model can be said to be more closely related to the experimental data than that predicted from the API model from the SSE and RMSE results.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.498-507
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• 2008

The mixture of bentonite powder and water is generally used to maintain the stability of excavation surface during the construction of vertical cutoff walls. The filter cake on the sidewall surface is the result of filtration of slurry into the adjacent soil formation. The filter cake is believed to have a very low hydraulic conductivity compared to that of the cutoff wall. This paper evaluates hydraulic conductivities of bentonite filter cakes set up with three types of bentonites under various pressure levels. A modified fluid loss test was employed in this experiment. Theory of filtration process was reviewed to explain the procedure in the present experiment. Hydraulic conductivity of the filter cakes with consideration of the filter medium resistance was evaluated. The results of the experiment with two calculation methods and discussion are presented to show the efficiency of the modified fluid loss test.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1502-1511
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• 2008

The mixture of bentonite powder and water is generally used to maintain the stability of excavation surface during the construction of vertical cutoff walls. The filter cake on the sidewall surface is the result of filtration of slurry into the adjacent soil formation. The filter cake is believed to have a very low hydraulic conductivity compared to that of the cutoff wall. This paper evaluates hydraulic conductivities of bentonite filter cakes set up with three types of bentonites under various pressure levels. A modified fluid loss test was employed in this experiment. Theory of filtration process was reviewed to explain the procedure in the present experiment. Hydraulic conductivity of the filter cakes with consideration of the filter medium resistance was evaluated. The results of the experiment with two calculation methods and discussion are presented to show the efficiency of the modified fluid loss test.

• 한국지반공학회논문집
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• 제18권4호
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• pp.239-248
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• 2002

안정액(bentonite slurry)을 이용한 지하연속벽의 건설은 굴착된 trench 내에서 안정액이 침투케익과 표면케익을 포함한 불투수막을 형성함으로서 trench 의 안정성을 유지할 수가 있다. 그러므로 구조용 지하연속벽 건설이나 폐기물 매립장의 차수용 연속벽 건설시 지반조건 및 주변여건의 변화에 의하여 여러 가지 문제가 발생 될 수 있다. 본 논문은 안정액 유출과 불투수케익 형성과정을 대형실험으로 모델링하여 그 결과가 slurry trench 안정성에 미치는 영향을 평가하고, 현장조건에 적합한 설계절차를 제시하였다.

• Geomechanics and Engineering
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• 제10권4호
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• pp.437-454
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• 2016

Wellbore instability problem is one of the main problems that met frequently during drilling, particularly in high temperature, high pressure (HPHT) formations. There are large amount of researches about wellbore stability in HPHT formations, which based on the thermo-poroelastic theory and some achievements were obtained; however, few studies have investigated on the fully coupled thermo-poroelastoplasticity analysis of wellbore stability, especially the analysis of wellbore stability while the filter cake formed. Therefore, it is very necessary to do some work. In this paper, the three-dimensional wellbore stability model which overall considering the effects of fully coupled thermo-poroelastoplasticity and filter cake is established based on the finite element method and Drucker-Prager failure criterion. The distribution of pore pressure, wellbore stress and plastic deformation under the conditions of different mud pressures, times and temperatures have been discussed. The results obtained in this paper can offer a great help on understanding the distribution of pore pressure and wellbore stress of wellbore in the HPHT formation for drilling engineers.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.1478-1486
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• 2009

As a conventional line-fitting method, the Bouwer and Rice method has been popularly adopted to estimate the hydraulic conductivity of an aquifer through a slug test. Because a ventical cutoff wall is usually very compressible and features a small wall thickness, the Bouwer and Rice method should be carefully used for the vertical cutoff wall. In addition, a relatively impermeable layer, called a filter cake, formed at the interface between the cutoff wall and the natural soil formation makes it difficult to use the Bouwer and Rice method directly. In order to overcome such limitations, the original Bouwer and Rice method is modified by incorporating the concept of the flow net method. In this modification, the geometry condition of cutoff walls including the filter cake is effectively considered in evaluating the hydraulic conductivity of a vertical cutoff wall.

• 한국지반공학회논문집
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• 제25권12호
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• pp.47-55
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• 2009

순간변위시험(Slug test)을 통해 대수층의 투수계수를 구할 때, 시험결과 해석에 적용하는 line-fitting법 중 가장 일반적인 방법이 Bouwer and Rice법이다. Bouwer and Rice법을 적용하여 압축성이 크고 벽체의 두께가 얇은 연직차수벽의 투수계수를 산정할 때는 세심한 주의가 필요하다. 그리고 연직 차수벽과 주변 지반 사이에 형성된 상대적으로 투수성이 낮은 영역, 즉 필터케이크(Filter cake)는 Bouwer and Rice법을 연직차수벽의 투수계수 산정시, 이 방법을 직접적용하기 어렵게 만든다. 본 논문에서는 기존의 Bouwer and Rice법의 한계를 극복하기 위해서 유선망 개념을 도입한 수정 Bouwer and Rice법을 제안하였다. 수정된 Bouwer and Rice법은 연직차수벽의 투수계수를 산정할 때 필터케이크를 포함한 연직차수벽의 기하학적 조건을 효율적으로 반영할 수 있도록 한다. 또한, 수정 Bouwer and Rice법의 적용성을 검증하기 위한 사례 연구가 본 논문에서 수행되었다.

• 한국막학회:학술대회논문집
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• 한국막학회 1998년도 춘계 총회 및 학술발표회
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• pp.105-109
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• 1998

1. Introduction : In microfiltration the transport, deposition and removal of particles control cake formation on a filter. In this connection a new model on cake formation, based on the wall shear stress, was tested here in comparison with experiments of fine particle slurry under Taylor-vortex flow. The model expresses the deposition process for particles as two first-order steps in series of mass transfer and adhesion, and their removal process as a linear relation to the wall shear stress. This embraces characteristics of both dead-end and crossflow filtration. The correlation resulting from fitting to experimental data represented the experimental data reasonably well. This study will be helpful in analyzing fouling in heat exchangers.

• 한국지반신소재학회논문집
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• 제5권2호
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• pp.31-37
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• 2006

본 논문에서 고함수비 슬러지와 퇴적물 탈수에 지오텍스타일 튜브의 이용가능성과 이에 영향을 미치는 요인들에 대한 평가를 수행하였다. 네 가지 고함수비물질을 사용하여 두 가지 지오텍스타일에 대해 다른 두 여과압력으로 실험을 실시하였다. 실험결과, 직포지오텍스타일 튜브는 일반적인 토사보유성기준을 만족하지 않지만 상류측의 필터케익 형성에 의해 세립자의 많은 부분을 유지하였고, 필터케익 형성 후, 투수성은 급속하게 감소하였다. 높은 여과압력은 탈수율을 증가시키는 경향이 있지만 여과효율에는 매우 적은 영향을 미치고, 탈수능력은 지오텍스타일에 관계된 여러 요인에 의해 영향을 받는데 슬러지 재료 자체의 특성이 탈수효율에 지배적인 요소로 나타남을 알 수 있었다.