Experimental Study on Muck Improvement of Clay Stratum in Earth Pressure Balance Shield

doi:10.12068/j.issn.1005-3026.2025.20230273

Abstract

Abstract:

When tunneling in clay stratum， the shield may encounter some problems such as “mud cake” on the cutterhead， soil accumulation in the chamber， and poor soil discharge. Therefore， based on the shield project between Wenchu Road Station and Guanyin Road Station of Shenyang Metro Line 6， muck improvement was carried out based on foaming ratio and half-life test， dispersant settlement test， rotating shear test， mobility test and stirring test. Finally， scanning electron microscopy， Zeta potential and double electric layer theory were used to analyze the mechanism of clay improvement by dispersant. The results show that the performance of the modifier is better when the volume fraction of foam agent is 4% and the sodium hexametaphosphate mass fraction is 2%. The improvement effect is better when the moisture content of soil layer is 30%， the dispersant injection ratio is 10% and the foam injection ratio is 30%~60%. Scanning electron microscopy and Zeta potential tests showed that 2% sodium hexametaphosphate solution can increase the thickness of the clay double electric layer and disperse the clay.

Key words: earth pressure balance（EPB） shield, muck improvement, electric double layer theory, clay stratum, evaluation index

CLC Number:

U 45

Meng LI, Wen ZHAO, Xin WANG, Xiao-di LIU. Experimental Study on Muck Improvement of Clay Stratum in Earth Pressure Balance Shield[J]. Journal of Northeastern University(Natural Science), 2025, 46(4): 106-114.

Figures/Tables 24

Fig.1 Clay sample

Fig.2 XRD test results

Fig.3 Particle size grading curve

Table 1 Physical parameters of soil layer

参数	试验方法	值
含水率/%	烘干法	25
塑限/%	液塑限联合测定法	23.11
液限/%	液塑限联合测定法	42.3
塑性指数	液塑限联合测定法	19.19
内摩擦角/(°)	直剪试验	12.7
黏聚力/kPa	直剪试验	31.6
压缩模量/MPa	压缩试验	6.84

Fig.4 Foam performance test

Fig.5 Foaming ratio and half-life change curves with the volume fraction of foam agent

Fig.6 Clay settlement test photo of dispersant

Fig.7 Curves of clay settlement thickness with mass fraction of dispersant solution

Fig.8 Soil conditioning test instrument

Table 2 Range of improver injection ratio

序号	改良剂名称	含水率	注入比
1	水	20	0，5，10，15，20，25
2	泡沫	20，25，30	15，30，45，60
3	分散剂	20，25，30	5，10，15，20
4	组合改良剂	30	泡沫：15，30，45，60
4	组合改良剂	30	分散剂：5，10，15，20

Fig.9 Test of fluidity and adhesion of clays with a moisturecontent of 35%~45%

Fig.10 Water reclamed soil test curves

Fig.11 Adhesion test curves of foam-modified soil

Fig.12 Fluidity test curves of foam-modified soil

Fig.13 Curves of rotary shear test of foam-modified soil

Fig.14 Adhesion test curves of soil improved by dispersant

Fig.15 Fluidity test curves of soil improved by dispersant

Fig.16 Curves of rotary shear test of soil improved by dispersant

Fig.17 Adhesion test curves of soil with dispersant and foam

Fig.18 Fluidity test curves of soil with dispersant and foam

Fig.19 Rotary shear test curves of soil with dispersant and foam

Fig.20 Microstructure characteristics of soil samples

Table 3 Amount of each component added during

六偏磷酸钠溶液添加比/%	加入水质量/g
0	1 000
2	998
4	996
6	994
8	992
10	990

Fig.21 Zeta potential changes with the addition ratio of sodium hexametaphosphate solution

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