Effect of Wood Fiber on the Strength of Calcareous Sand Rapidly Seeped by Colloidal Silica

Weifeng Jin,Rongzhong Chen,Zehai Cheng,Xin Wang,H Li,I Corbi,O Corbi,M Ashraf,L Wang,P Yang

doi:10.1051/matecconf/201927503006

Weifeng Jin, Rongzhong Chen + Show 8 more

Open Access

https://doi.org/10.1051/matecconf/201927503006

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Abstract

Silica nano-particles are suspended in the colloidal silica and can be induced to gradually gel after the PH value changes. Thus colloidal silica can be utilized to rapidly seep through loose calcareous sand, and the silicon gel is gradually formed to bond sand particles. However, based on observation by scanning electron microscope(SEM), there are a lot of microcracks in the silica gel, which reduces the strength of the sand-gel composite. Therefore, in order to suppress crack growth, wood fibers are dispersed in the colloidal silica which still can seep through calcareous sand. 18 silicon-gel stabilized sand samples were prepared for tri-axial tests, where the concentration of colloidal silica is 20%, and wood fiber concentrations are 0%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, respectively. The results show that:(1) there exists an optimum ratio of wood fiber to colloidal silica, that is, as the concentration of wood fiber increases, the strength represented by the peak value of deviator stress rises first and then falls; (2) there are opposite trends between the two strength parameters, internal friction angle and cohesion, that is, when the wood fiber concentration is 0.04%, the cohesion reaches the maximum value and the internal friction angle reaches the minimum value; (3) The photos by SEM show that, there are wood fibers on the inner wall of the crack in the silica gel, which may reduce the extent of crack propagation and contribute to the strength of stabilized sand samples.

Highlights

Biological effects such as corals and seashells form marine calcareous sands which are widely distributed.Calcareous sands are used to make artificial islands in the ocean and serve as subgrades for shipping terminals.calcareous sands are easy to break, which are different from non-crushable silica sands
Microbial induced calcite precipitation (MICP) utilizes bacteria metabolic activities to produce insoluble CaCO3 which bonds sand particles, and liquefaction resistance of microbial induced calcite precipitation (MICP) stabilized calcareous sand was studied by dynamic tri-axial tests
In the hope that wood fiber would inhibit crack propagation in the gel, this paper attempts to disperse wood fiber in the colloidal silica, and inspects the microscopic mechanism and the reinforcement effect of wood fiber on calcareous sand seeped by colloidal silica

Summary

Introduction

Biological effects such as corals and seashells form marine calcareous sands which are widely distributed. Microbial induced calcite precipitation (MICP) utilizes bacteria metabolic activities to produce insoluble CaCO3 which bonds sand particles, and liquefaction resistance of MICP stabilized calcareous sand was studied by dynamic tri-axial tests [6]. Another stabilization method for loose sand is to use colloidal silica. Studied [7,8] Different tests, such as full-scale explosion test [9], centrifuge tests [10,11,12] and tri-axial tests [13,14,15,16,17] were carried out to evaluate liquefaction mitigation of loose sand treated by colloidal silica. In the hope that wood fiber would inhibit crack propagation in the gel, this paper attempts to disperse wood fiber in the colloidal silica, and inspects the microscopic mechanism and the reinforcement effect of wood fiber on calcareous sand seeped by colloidal silica

Experimental materials and sample preparation

Testing scheme

Results and discussion

Conclusion