Download Mechanical Properties of Adobe Bricks Determined with Triaxial

Mechanical Properties of
Programme: MSc Civil Engineering
Name of Student: Xinwei Guo
Supervisor: Dr. Pedro Ferreira
Adobe Bricks Determined with
UCL Department of Civil, Environmental
and Geomatic Engineering, Gower St,
London ,WC1E 6BT
Triaxial Testing
1. Introduction
2. Objectives
The material
Objectives
Adobe bricks is a widely used masonry material in many
traditional constructions, and many of them are still in use.
The word ‘Adobe’ came from the Arabic word Al-Twoob, and
the meaning of the word is ‘the sun-dried mud brick’(Aqtash
2014). It has been verified to have excellent cost and
mechanical performance, especially under compressive
loadings. The raw materials for making Adobe are mostly
obtained locally, including soil, organic fibres, water, lime and
cements, and the exactly composition varies with the
location, age of producing, producers and batches.
• To test cylindrical Adobe bricks samples under different
confining pressures following routine triaxial test
procedures.
• To investigate the stiffness of Adobe bricks under shear.
• To determine the shear parameters (cohesion caused by
cementing and frictional angle).
• To analyse the influences of cementation on critical state
and shear parameters.
3. Methodology
Making of Adobe bricks
The making of Adobe bricks is very simple. As stated by
Illampas et al. (2014) and Aqtash (2014), they are
traditionally produced in warm summer by mixing soil,
organic fibres and water to plastic consistency, and then the
mixture is cast into timber moulds and allowed to naturally
dry (preferably in the shade) without any artificial firing.
Before mixing the raw materials, it is preferable to soak the
dry soil and break any clay chunks in it. And this process has
not changed significantly over time.
Sample
preparation (4
intact and 1
remoulded)
Data collection
Percolation
Shear
Saturation
Consolidation
4. Summary of results
Deviator Stress-Effective Mean Stress
Specific Volume-lnp'
1200
2.4
2.3
1000
800
Specific Volume
Dviator Stress (kPa)
2.2
600
400
2.1
2
1.9
1.8
1.7
200
1.6
1.5
0
0
100
200
300
400
500
600
0
1
2
Effective Mean Stress (kPa)
50kPa
100kPa
150kPa
200kPa
Critical state in q’-p’ form for intact samples with confining
pressures: 50 kPa, 100 kPa, 150 kPa and 200 kPa
2.8
3
4
5
6
lnp'
50kPa
100 kPa
150 kPa
200 kPa
150 Remoulded
V-lnp’ graph for isotropic consolidation for intact samples
and a remoulded sample with a confining pressure of 150
kPa, giving the reference range of cohesion: 55 - 65kPa.
5. Conclusion
Mohr circles for intact samples. Reference cohesion for
cementing: 60 kPa. Cemented friction angle: 41 ° (intrinsic
value 45 °).
• Intrinsic friction angle: 45 °. Cementing fail between 55 –
65 kPa confining pressure. Cemented friction angle: 41 °.
• At critical state, q’/p’ for decemented intact samples is
1.7, the value for cemented samples (low pressures) is
1.97. Stiffness varies between 30 MPa to 150 MPa.
• Failure mode:
Intact samples: shear plane slip.
Remoulded sample: barreling.
• More numbers of remoulded samples and low confining
pressure intact sample tests are suggested for future
research.
References:
Aqtash, U.A.L., 2014. PhD dissertation: An experimental and numerical study of the moisture effects on soil strength and performance of Adobe walls. Las Cruces: New Mexico State University.
Illampas, R., Ioannou, I. & Charmpis, D.C., 2014. Adobe bricks under compression: Experimental investigation and derivation of stress-strain equation. Construction and Building Materials, 53, pp.83–90.
Silveira, D. et al., 2012. Mechanical properties of adobe bricks in ancient constructions. Construction and Building Materials, 28(1), pp.36–44.