Performance evaluation of rigid inclusions for settlement control of grain silos in tropical soils

Rebolledo, Juan Félix Rodríguez; Santiago, Isabelle Moreira; Bernardes, Heitor Cardoso; Mendes, Thiago Augusto

doi:10.28927/SR.2022.004822

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Article • Soil. Rocks 45 (4) • 2022 • https://doi.org/10.28927/SR.2022.004822 copy

Performance evaluation of rigid inclusions for settlement control of grain silos in tropical soils

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

This study presents the evaluation of the performance of grain silos reinforced by rigid inclusions in soils of the Central-West region of Brazil, during its construction and operation. Therefore, a group of eight silos with 32.4 m in diameter, 30 m in height, and 12,000 t of storage capacity (each silo) was numerically analyzed using the three-dimensional Finite Element Method (FEM, Plaxis 3D). The stratigraphy of the Experimental Field of the University of Brasilia, Brazil (CEGUnB) was considered in the analysis. The performance of using a system of rigid inclusions to reinforce the soil beneath the raft was compared with the behavior of an isolated raft. Two models were developed: in the first one, an independent silo was considered, its behavior was analyzed during its construction and operation stages by varying the length of the inclusions; in the second model, the group of eight silos was considered and their behavior was studied for different combinations of loading. The rigid inclusions system proved to be an efficient foundation solution that allows controlling total and differential displacements during the construction and serviceability stages of the silo, helping to prevent the formation of cracks in the structural elements and grain contamination by the excessive opening of the raft-perimeter beam structural joint.

Keywords
Grain silos; Rigid inclusions; Serviceability limit-state; 3D numerical modeling; Finite element method; Tropical soils

Parameters	Layer number
	1		2		3	4	5	6
	Porous sandy clay					Lateritic residual soil		Saprolitic soil
Depth (m)	0 - 1.5		1.5 - 3.5		3.5 - 5.0	5.0 - 7.0	7.0 - 8.5	8.5 - 20.0
State	Nat.	Sat.	Nat.	Sat.	Nat.	Nat.	Nat.	Nat.
γ (kN/m³)	13.1	16.5	12.8	16.4	13.9	14.3	16.0	18.2
c' (kPa)	5	0	5	0	5	20	75	20
ϕ' (°)	25	26	25	26	26	32	20	22
ψ (°)	0	0	0	0	0	0	0	0
$E_{50}^{r e f}$ (MPa)	3.2	2.2	2.5	2.1	4.0	12.0	13.2	12.2
$E_{o e d}^{r e f}$ (MPa)	4.9	1.0	1.5	0.8	2.2	6.9	7.0	5.7
$E_{u r}^{r e f}$ (MPa)	14.0	13.0	14.0	13.0	36.9	37.5	54.0	54.0
m	0.50	0.65	0.50	0.80	0.50	0.50	0.50	0.70
$ν_{u r}$	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2
$p^{r e f}$ (kPa)	100	50	100	50	100	100	100	100
$R_{f}$	0.80	0.75	0.80	0.75	0.90	0.90	0.90	0.80
POP (kPa)	65.7	16.1	31.8	6.6	0.0	31.4	0.0	0.0
$K_{o}^{n c}$	0.58	0.56	0.58	0.56	0.56	0.47	0.66	0.63
$K_{o}$	1.37	0.75	0.77	0.75	0.56	0.56	0.66	0.63

Parameter	Value
Unit weight, γ (kN/m³)	18.6
Young’s modulus, E (MPa)	60
Cohesion, c' (kPa)	80
Friction angle, ϕ' (°)	38
Poisson’s ratio, ν	0.33

a) Parameters for plate elements
Parameter	Inclusion cap		Perimeter beam		Raft		Tunnel
Thickness, d (m)	0.1		0.4		0.2		0.2
Unit weight, γ (kN/m³)	24		24		24		24
Young’s modulus, E (GPa)	25		25		25		25
Poisson’s ratio, ν	0.2		0.2		0.2		0.2
b) Parameters for aeration ducts (beam elements)
Parameter	Value	Cross section
Young’s modulus, E (GPa)	25
Unit weight, γ (kN/m³)	24
Cross section, A (m²)	0.56
Inertia around 2^nd axis (m⁴)	0.0875
Inertia around 3^rd axis (m⁴)	0.0454
c) Parameters for embedded beams
Parameter	Piles	Inclusions
Length, L_pile (m)	20	5		10		15		20
Young’s modulus, E (GPa)	25.0	17.7		17.7		17.7		17.7
Unit weight, γ (kN/m³)	24	23		23		23		23
Diameter, D (m)	0.35	0.35		0.35		0.35		0.35
Side friction resistance, T_sf (kN/m)	53.6	18.7		42.6		53.6		66.3
Base resistance, F_max (kN)	37.2	46.9		30.6		37.2		46.3
Total resistance, N_pile (kN)^*	841.2	140.4		456.6		841.2		1372.3

Stage	Characteristics
1	Initial stress conditions
2	Silo construction. Applied load on the perimeter beam = 183.1 kN/m
3	Total filling of the silo. Applied load on the silo raft = 135.3 kPa
4	Total discharge of the silo raft.

Comb.	Silos	SRF	DRF	GRF
Individual silo behavior		0.70	0.92	0.84
1	External (01, 04, 05, 08)	0.67	0.90	0.83
1	Internal (02, 03, 06, 07)	0.17	0.17	0.09
2	External (01, 04, 05, 08)	0.20	0.20	0.13
2	Internal (02, 03, 06, 07)	0.66	0.90	0.84
3	External (01, 04, 05, 08)	0.66	0.92	0.84
3	Internal (02, 03, 06, 07)	0.66	0.93	0.85

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[1] #Corresponding author. E-mail address: heitor.bernardes@ifgoiano.edu.br