Experimental analyses of high-filled cut-and-cover tunnel for reduction of the earth pressure

Figures & data

Figure 1. Comparison between stress results by ABAQS and PLAXIS 3D.

Figure 2. Comparison between displacements results by ABAQS and PLAXIS.

Figure 3. Schematic view of the physical model configuration for loading system.

Figure 4. Schematic S-S side view of the physical model.

Figure 5. Test setup and measurement tools.

Table 1. Comparison between properties of backfill and rubber-sand mixture.

Mechanical parameters	unit	Backfill	Rubber-Sand
Specific Gravity	—	2.65	2.01
Maximum dry unit weight	KN/m^3	17.7	15.3
Minimum dry unit weight	KN/m^3	15.1	12.6
Maximum void ratio	%	0.74	0.6
Minimum void ratio	%	0.50	0.3
Cohesion	KN/m^2	0	9
Angle of internal friction	o	40	35

Figure 6. Geogrid used in this study: (A) Netlon geogrid, (B) Tensile force stress diagram [17].

Table 2. The mechanical characteristics of both the CCT prototype and the model.

Mechanical parameters	Model	Prototype	Poisson ratio
Elastic modulus (GPa)	31	0.9	0.2
Uniaxial compressive strength (MPa)	22.5	0.7	0.2

Figure 7. (A) Uniaxial compression test, (B) steel mesh, (C) strain gauge on CCT.

Table 3. Testing schemes.

Case	Load Reduction Method	Placement (L)	Thickness/Type
S1	None	None	None
S2	Rubber-Sand	42cm	12cm
S3	Rubber-Sand	48cm	18cm
S4	Rubber-Sand	54cm	24cm
S5	Geo-Grid	39cm	Biaxial
S6	Geo-Grid	42cm	Biaxial
S7	Geo-Grid	45cm	Biaxial

Figure 8. Stress strain curve for CCT under applied pressure on foundation.

Figure 9. Earth pressure on CCT under pressure footing 18Kpa along the horizontal axis.

Figure 10. Case S2 (T = 0.6 H).

Figure 11. Case S3 (T=0.9 H).

Figure 12. Case S4 (T=1.1 H).

Figure 13. Effect of using rubber-sand in earth reduction.

Figure 14. Case S5 (L=0.95 H).

Figure 15. Case S6 (L=1.1 H).

Figure 16. Case S7 (L=1.25 H).

Figure 17. Comparison between geo-grid samples.

Figure 18. Comparison between earth pressure reduction in different methods.

Ahmad H. Sustainability effect of geogrid reinforced tire-shred sand mixtures on the load pressure-settlement response of shallow footing. Heliyon. 2022;8(11):e11743. doi: 10.1016/j.heliyon.2022.e11743

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