EVALUATION OF THE SEISMIC VULNERABILITY OF PERUVIAN TRADITIONAL DRY STONE RETAINING
WALLS (PIRCAS): Experimental and numerical approach
Sandra Santa-Cruz Hidalgo
Dominique Daudon
Paola Ita
Grenoble, October 20th
2
Scope
• Introduction and definitions
• Characterization of pircas
• Analysis Experimental and Numerical
•
Recommendations
3
Sloped lands occupation in highlands has been well addressed by ancient techniques with Dry Stone Retaining Walls
3
pirqa = Wall
Cusco- Peru
In Lima, 3 million people lives in terraces
4
Carabayllo Sector el Progreso
Pirca
Out-of-planeforces
ecanismo de resistencia en juntas
Muro: DSRW Pircas
Efecto: Fricción Trabazón
Parámetros 1: Ángulo de fricción Cohesión ficticia
Parámetros 2: Ángulo de fricción Ángulo de fricción adicional
6
7
(Zavala, 2018) (Zavala et al, 2018)
Pisco earthquake (2007) Magnitude 7.9Mw
Cañete earthquake (2021) Magnitude 6.0Mw
Some pircas have partially or totally collapsed due to the past earthquakes.
MML (Municipalidad de Lima), 2013. Guía para la habilitación urbana en asentamientos humanos. Lima.
51% se mantienen en uso
33% uso es temporal
16% derruidos y sin uso Castro, Vallejo, & Estrada, 2017; Gonzales Ramos, 2008; Kendall & Rodríguez, 2001, 2009; PRONAMACHCS, 1984.
10
TIPOS DE PIRCAS
1.Piedrasgranes8"
2.Piedraschicas4"
3.Sacosde arena
4.Llantasrellenas
5.Sacosrellenosconotro material
TIPO DE ROCA
1. Redonda 2. Angular 3. Cuadrada 4. Otros
TIPOS DE PIRCAS
2. Piedras chicas4"
3. Sacos de arena
4. Llantas rellenas
5. Sacos rellenos conotro material
6. Residuos delaconstruccion desmonte
7. Materialconbasura
8. Otros
20%
6.Residuosdelaconstruccion desmonte
8.Otros voids 30-40%
7.Materialconbasura
200- 500 mm 20%
0% 0% 0% 0% 0%4%
11 1% 93% 3%3%
Source: NGO Soluciones Prácticas 76%
0% 0% 0% 0% 0%4%
1. Piedras granes 8"
12
Construction process
13
14
Key definitions :
• Through Stone: Stone of length equal to the width of the wall, whose function is to unite the two faces of the wall.
• Overlap: Partially or totally cover one stone over another in order to unite (tie) the section of the wall.
Through Stone
We built and tested 6 natural escale specimens
Plataforma inclinable
2 hydraulic pistons
1 hyd.pump. 2HP
Electronic control panel. (30 A, 220 V)
Pseudo-static tests :
F out-of –plane= W x sin (angle)
F out of plane
18
W
α
FN
V N
Stopper
Control points:
control points
View of the work area
Displacements out of plane:
Where:
Δ= deformation wall height
1 2 3 4 5 6 7 8 9 10 11 12 d
d=
h d final position initial Position
z y x z y z y
deformation h= wall height Δ= drift
Pseudo-static tests :
Specimen-1 Specimen-2 Specimen-3 Specimen-4 Specimen-6 Specimen-5
Type 1: Length (L) : 4.00 m
Width (B) :0.45 m
Height (H): 1.00 m
Type 2: Length (L) : 4.00 m
Width (B) : 0.60 m
Height (H): 1.50 m
Collapse Mechanisms:
Type 1 failure:partial or total delamination of the cross-section and overturning of the delaminated section
(the frontal face begins to separate from the back face, and then the first one rotates)
Delamination:
Note: The collapse mechanism focuses on the 2D effect presented in the cross section.
Delamination is similar to a break or cut running along a surface perpendicular to the cross-section.
22
Collapse Mechanisms:
Type 2 failure : displacement of a section by partial or total delamination
Note: The collapse mechanism focuses on the 2D effect presented in the cross section.
23
Collapse Mechanisms:
Type 3 failure : overturning of the entire (or almost) wall section
24
0% 5% 10% 15% 20% 25% 30% 35% - 0.005 0.010 0.015 0.020 0.025 Shear base capacity /weight average drift specimen 1 specimen 2 specimen 3 average 0% 5% 10% 15% 20% 25% 30% 35% - 0.005 0.010 0.015 0.020 0.025 Shear base capacity /weight average drift specimen 4 specimen 5 specimen 6 average H N Collapse angle (°) V/W (%) 1.0 m 1 16.6 29 Average 31% CV=7% 2 17.2 30 3 20.0 34 1.5 m 4 14.2 25 Average 25% CV=3% 5 15.1 24 6 15.2 26
Results
Carabayllo PGA(g) Tr=475 years 1.00 0.38 Level PGA (g) PGA*: con amplificación topográfica (x1.2) Frequent 0.18 0.22 Ocasional 0.22 0.27 Design 0.42 0.51 PSHA
H (m) Ángulo de colapso promedio(º) Fhresistent e/W V H= 1m 18 31% 29% H = 1.5 m 15 25% 32% Seismic Analysis Out-of-plane V PGA=0.27 g
Results:
• Traditional pircas are not safety for an occasional earthquake in Lima City
• Experimental results have shown that the primary collapse mechanism in pircas is due to delamination and block-overturning of the walls. The behavior in both cases is fragile since there is slight displacement before collapse (the average drift related to delamination is 1.4% and 1.6% for overturning).
• For the 1 m height walls, the lack of Through stones causes the wall’s delamination. It was measured with an initial stiffness reduction of up to 60 % .
• It is necessary to carry out more studies to find the most optimal arrangement (transverse and longitudinal configuration) that improves the behavior of the pircas.
Pircas are the most vulnerable part of the houses in Lima’s hills
0 10 20 30 40 50 60 70 80 90 100 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 % Daño estructural PGA(g) Madera Mampostería simple No Tecnificado Pirca H = 1m Pirca H = 1.5m
Ramos V. (2021) Evaluación del riesgo sísmico en viviendas sobre pircas en un asentamiento humano en el distrito de Villa María del Triunfo. Tesis para optar al título de Ingeniero Civil. Pontificia Universidad Católica del Perú. Lima
Can we improve the out-of-plane performance of pircas by improving the construction technique?
0% 5% 10% 15% 20% 25% 30% 35% - 0.005 0.010 0.015 Shear base capacity /weigth average drift wall 1 wall 2 wall 3
Three wall arrangements were considered
Collapse mechanisms obtained:
Case 1 Case 2 Case 3
One kind of failure was due the delamination of the cross section
Numerical modeling results:
Numerical cases: Case 1 , Case 2 and Case 3
34 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 0 5 10 15 20 25 30 Inclination ( ° ) Friction angle(ф) Collapse angle (°) Case 3 Case 1 Case 2 Specimen 5 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0 0.02 0.04 0.06 Shear base capacity / weight average drift Capacity curve(h=1.5m)_ф=20°
Case 1 Case 2 Case 3
•
Resultados de traducción
Dimensions: Length: 4.0m Height: 1.50m Width: 0.60m
Parameters for the construction : 3 specimens were built for each arrangement
The main parameter for construction is the through stones. The quantity and position of these tie elements defines the configuration.
Dimensions:
Length: 4.0m
Height: 1.50m
Width: 0.60m
Arrangement 1
23 Through Stone
: Through Stone
Arrangement 2
16 Through Stone
Arrangement 3
14 Through Stone
Resultados de traducción
Dimensions: Length: 4.0m Height: 1.50m Width: 0.60m
Parameters for the construction : 3 specimens were built for each arrangement
The main parameter for construction is the through stones. The quantity and position of these tie elements defines the configuration.
Dimensions:
Length: 4.0m
Height: 1.50m
Width: 0.60m
Arrangement 1
23 Through Stone
: Through Stone
Arrangement 2
16 Through Stone
Arrangement 3
14 Through Stone
Results obtained:
The use of Through Stone improves the out-of-plane resistance of the ‘’pircas’’(comparing the experimental tests of 2020 versus 2022)
Arrangement 0 * Arrangement 1
6 Through Stone
23 Through Stone
Experimental tests
Arrangement Average Fh/W% increase *(%)
* Increase with respect to the average value of the arrangement 0 (2020)
•
0
25% 1 37% 50% 2 35% 41% 3 34% 35%
0.0% 5.0% 10.0% 15.0% 20.0% 25.0% 30.0% 35.0% 40.0% 45.0% 0 0.01 0.02 0.03 0.04 0.05 0.06 Shear base capacity /weight Average drift Capacity Curve (Arrangement 0 vs Arrangement 1) Arrangement 1_S4 Arrangement 1_S8 Arrangement 0_Average
Results obtained:
• The use of Through Stone improves the out-of-plane resistance of the ‘’pircas’’(comparing the experimental tests of 2020 versus 2022)
Arrangement 0 * Arrangement 2
Arrangement 2_S2
Arrangement 2_S9
Arrangement 2_S5
Arrangement 0_Average
6 Through Stone
Experimental tests
Arrangement Average Fh/W% increase *(%) 0 25%
1 37% 50%
2 35% 41%
3 34% 35%
* Increase with respect to the average value of the arrangement 0 (2020)
Note: * Configuration_0 has approximately 6 Through Stones, position control was not performed, referential image
16 Through Stone
0.0% 5.0% 10.0% 15.0% 20.0% 25.0% 30.0% 35.0% 40.0% 45.0% 0.0000 0.0100 0.0200 0.0300 0.0400 0.0500 0.0600 Shear base capacity /weight Average drift Capacity Curve (Arrangement
Arrangement
0 vs
2)
Results obtained:
• The use of Through Stone improves the out-of-plane resistance of the ‘’pircas’’(comparing the experimental tests of 2020 versus 2022)
Arrangement 0 * Arrangement 3
Arrangement 3_S3
Arrangement 3_S6
Arrangement 0_Average
6 Through Stone
Experimental tests
Arrangement Average Fh/W% increase *(%) 0 25%
1 37% 50%
2 35% 41%
3 34% 35%
* Increase with respect to the average value of the arrangement 0 (2020)
Note: * Configuration_0 has approximately 6 Through Stones, position control was not performed, referential image
14 Through Stone
0.0% 5.0% 10.0% 15.0% 20.0% 25.0% 30.0% 35.0% 40.0% 0.0000 0.0100 0.0200 0.0300 0.0400 0.0500 0.0600 Shear base capacity /weight Average drift Capacity Curve (Arrangement 0 vs Arrangement 3)
As the arrangement presents fewer Through Stones, a greater coefficient of variation is presented in the results.
•
39 36 39 3433 38 34 29 0 5 10 15 20 25 30 35 40 45 Fh/W (%) Arrangement specimen 8 specimen 4 specimen 2 specimen 9 specimen 5 specimen 3 specimen 6 specimen 10 2 3 1 Arrangement Coefficient of variation (%) Arrangement 1 6% Arrangement 2
Arrangement 3 13%
10%
Seismic Analysis
H (m) Ángulo de colapso promedio(º) Fhresistent e/W V required H = 1.5 m 15 25% x 1.5 =38% 51%
Out-of-plane V PGA=0.27 g Experimental tests Arrangement Average Fh/W% increase *(%) 0 25% 1 37% 50% 2 35% 41% 3 34% 35%
Increase with respect to the average value of the arrangement 0 (2020)
*
Conclusion
• Pircas can improve its capacity up to 50% by using properly the units without any mortar
• Through stones are neccesary to avoid delamination as well as overlapping, to avoid ocal failures
• Eventhough, we do not recomend the use of pircas for housing because the level of safety os not similar to the one requiered by the peruvian government.
• Instead, pircas can be used for risk reduction and protections of natural and Green áreas
• There is a opportunity for Strengthening capabilities and social inclusion
42
“Lomas” Costa Verde
Acknowledgements
Project grant CAP 2021-PI0770
Contract P21P01 – ECOS NORD
Contract 019-2021 – FONDECYT- ECOS NORD
Project 109-2017-FONDECYT .
44
Bibliografia
• S Santa-Cruz, D Daudon, N Tarque, C Zanelli, J Alcántara (2021) Out-ofplane analysis of dry-stone walls using a pseudo-static experimental and numerical approach in scaled-down specimens. Engineering Structures 245, 112875
• Rivas, G. Y.; Quispe, E. A. y Santa-Cruz, S. C. (2019). State of the art of DSRW test equipment subjected to side loads and equipment proposal for static testing at natural scale. Tecnia , 2 (29), pp. 39-47. http://revistas.uni.edu.pe/index.php/tecnia/article/view/702/1104
• Zanelli, C. T.; Santa Cruz, S. C.; Valderrama, N. V. y Daudon, D. (2018). Assessment of Vulnerability Curves of Pircas over Slopes by the Discrete Element Method (DEM) A Case Study in Carabayllo, Peru. In Geotechnical Earthquake Engineering and Soil Dynamics V. (pp. 66-78) CALIFORNIA: ASCE.
