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WEATHERING INFLUENCE ON STRUCTURES

ROBERT HACK FACULTY OF GEO-INFORMATION SCIENCE AND EARTH OBSERVATION (ITC), UNIVERSITY OF TWENTE, THE NETHERLANDS.

PHONE:+31 (0)6 24505442; EMAIL: [email protected]

ITC, The Netherlands; 30 October 2012 INFLUENCE ON ENGINEERING STRUCTURES

Robert Hack Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, Enschede, The Netherlands, [email protected]

ABSTRACT An overview is given of the influence of weathering on engineering structures in and on natural materials. Some recently developed new ideas to incorporate weathering in design are discussed. All natural materials near and sometimes also deeper below surface of the Earth are subject to weathering. Notoriously difficult to forecast is the geotechnical behaviour due to future deterioration of the ground mass under influence of weathering. Weathering is a strongly local feature influenced by local circumstances such as local climate and weather, , and humans. Calculation methods and parameters used in design of engineering structures often do not properly anticipate the degradation of natural materials due to weathering. Preliminary failure, i.e. failure of the engineering structure before the end of the planned lifetime, may be the consequence. Slopes and start to raffle or may fail completely, and even buried foundations may be affected.

. what is weathering in engineering . implications for engineering . forecasting weathering . weathering rate

Weathering influence on engineering structures - Hack 30/10/2012 2 WEATHERING

. Physical, chemical, and biological alteration of and soil over time;

. Influenced by the atmosphere and the hydrosphere, and

. Cause rock or soil material to fall apart into smaller pieces or to dissolve in water.

Weathering influence on engineering structures - Hack 30/10/2012 3 STRESS RELIEF

Due to change in stress field (orientation or magnitude) discontinuities may form or existing discontinuities may open

(discontinuities are bedding planes, joints, fractures, etc.)

Weathering influence on engineering structures - Hack 30/10/2012 4 WEATHERING & STRESS RELIEF

Difference between effects of weathering and stress relief difficult to distinguish:

Therefore in engineering taken together as being “weathering”

Weathering influence on engineering structures - Hack 30/10/2012 5 EFFECTS OF WEATHERING

• weakening of intact rock blocks and soil grains • integral become mechanical discontinuities (i.e. bedding planes not being yet a mechanical plane of weakness become a mechanical plane of weakness) • material between rock blocks becomes weaker (remains of weathered material)

Weathering influence on engineering structures - Hack 30/10/2012 6 WHAT GIVES ROCK AND SOIL MASSES STRENGTH

Rock and soil masses consist of:

• intact blocks (rock) with discontinuities in-between (e.g. bedding planes, joints, fractures, etc) • grains (in soil) with grain contacts in-between

Strength of a mass is given by:

• strength (shear & tensile) of intact rock blocks or soil grains • shear strength between blocks (rock) or grains (soil)

Weathering influence on engineering structures - Hack 30/10/2012 7 ENGINEERING EFFECTS

. weaker rock blocks and soil grains . smaller rock blocks and grains . shear strength between blocks and grains less

Weathering influence on engineering structures - Hack 30/10/2012 8 Weathering influence on engineering structures - Hack 30/10/2012 9 reduction intact rock strength due to solution of cement (2)

blocks falling from disintegrating wall

Children playground made around 1995 Vandellos, Spain (photos: Hack, 2002) Weathering influence on engineering structures - Hack 30/10/2012 10 REDUCTION BLOCK SIZE

SAME MATERIAL THE MORE EXPOSED THE SMALLER THE BLOCK SIZE

Weathering influence on engineering structures - Hack 30/10/2012 11 shear strength reduction between blocks and grains (1)

bedding planes April 1990 CINDARTO SLOPE: VARIATION IN CLAY CONTENT IN INTACT ROCK CAUSES DIFFERENTIAL WEATHERING

Slightly higher clay content on bedding plane WeatheringSlope influence Stability on engineering by Classification structures - -Hack Hack 30/10/2012 1212 shear strength reduction between blocks and grains (2) CINDARTO SLOPE VARIATION IN CLAY CONTENT IN INTACT ROCK CAUSES DIFFERENTIAL WEATHERING

April 1992

mass slid

WeatheringSlope influence Stability on engineering by Classification structures - -Hack Hack 30/10/2012 1313 shear strength reduction between blocks and grains (3) carbonate is dissolved at bedding plane – clay remains

Weathering influence on engineering structures - Hack 30/10/2012 14 Degrees of weathering DEGREES OF WEATHERING

Weathering influence on engineering structures - Hack 30/10/2012 15 IMPACT OF WEATHERING

From: De Mulder, E.J.F., Hack, H.R.G.K., Van Ree, C.C.D.F., 2012. Sustainable Development and Management of the Shallow Subsurface. The Geological Society, London. ISBN: 978-1-86239-343-1. p. 192.

Weathering influence on engineering structures - Hack 30/10/2012 16 WEATHERING IN TIME

weathering rate depends on: . local climate & weather (e.g. wind direction) . groundwater . land-use (fertilizer) . does it stay exposed or is it covered by weathered material () . method of excavation

Weathering influence on engineering structures - Hack 30/10/2012 17 WEATHERING & TIME

Weathering based on rock & soil dissolution back analyses: rate [mm/y] average world 0.006 cold climate < 0.001 (Olvmo, 2010) warmer climate > 0.1 tropics metamorphic 0.04 Brazil (Moreira-Nordemann, 1980) rock mass tropics silica rock mass 0.058 Puerto Rico (White et al., 1998) mountainous areas mm's with high erosion rates

Intro Weathering - Hack 28/09/2012 18 WEATHERING & TIME

. Dissolution in 50 years thus around ½ to 5 mm . Dissolution in particular around discontinuities . Dissolution in the order of fraction of mm . Fraction of mm enough to reduce (shear) strength

Hence, even in relative short time spans of 50 to 100 years, weathering may have a substantial negative influence on properties of soil and rock masses

Weathering influence on engineering structures - Hack 30/10/2012 19 . Cleopatra’s needle Central Park, New York

1881

2011 copyright: michael martine, 2011

Weathering influence on engineering structures - Hack 30/10/2012 20 INFLUENCE WEATHERING ON DESIGN

Weathering influence on engineering structures - Hack 30/10/2012 21 Poor blasting of slope caused increased permeability and consequently allowed for loss of structure and rapid weathering of thin clay inter-bedded softer layers

Weathering influence on engineering structures - Hack 30/10/2012 22 POORLY BLASTED SLOPE

. 1990: new cut: slope height 13.8 m high, dip 70°

. 2002: slope dip about 55°

. 2005: slope dip about 52°

. SSPC forecast final stability: slope dip about 45°

(SSPC after Hack et al, 2003)

Weathering influence on engineering structures - Hack 30/10/2012 23 Diabase (subvolcanic rock Silver Creek Cliff , Route 61, equivalent to volcanic basalt) Duluth, MN, USA

made in: 1995 photos: 2011

Road protection wall built in 2010 to prevent stones on the road

BLASTING DAMAGE CAUSES RAPID RAVELLING AND LOSS OF STRUCTURE AND (photos: Hack, 2011)

CONSEQUENTLY WEATHERING Weathering influence on engineering structures - Hack 30/10/2012 24 debris

Fine grained calcareous mudstone falling apart within a couple of years after excavation

South Korea debris

(photos Hack, 2008)Weathering influence on engineering structures - Hack 30/10/2012 25

FUTURE DEGRADATION

Weathering influence on engineering structures - Hack 30/10/2012 26 FUTURE DEGRADATION

Reduction in slope 3.5 angle due to weathering, 3.0 erosion and ravelling (after 2.5 Huisman et al, 2006) z [m] 2.0

1.5

1.0 7.0 7.5 8.0 8.5 9.0 9.5 y [m] Excavated 1999 May 2001 May 2002 Weathering influence on engineering structures - Hack 30/10/2012 27 FUTURE DEGRADATION

Main processes involved in degradation: . Loss of structure due to stress release . Weathering (In-situ change by inside or outside influences) . Erosion (Material transport with no chemical or structural changes)

Weathering influence on engineering structures - Hack 30/10/2012 28 WEATHERING RATE

. The susceptibility to weathering is a concept that is frequently addressed by “the” weathering rate of a rock material or mass. . Weathering rates may be expected to decrease with time, as the state of the rock mass becomes more and more in equilibrium with its surroundings.

Weathering influence on engineering structures - Hack 30/10/2012 29 app WE( t) =−+ WEinit R WE log( 1 t)

WE(t) = degree of weathering at time t WEinit = (initial) degree of weathering at time t = 0 app R WE = weathering intensity rate

WE as function of time, initial weathering and the weathering intensity rate

Weathering influence on engineering structures - Hack 30/10/2012 30 GYPSUM CLAYSTONE SLOPE IN VANDELLOS

SSPC system with applying weathering intensity rate: . - original slope cut about 50º (1998) . - in 15 years decrease to 35º

Weathering influence on engineering structures - Hack 30/10/2012 31 KOTA KINABALU, MALAYSIA

10 years old

Weathering influence on engineering structures(after -Tating Hack , Hack,30/10/2012 & Jetten , 2011)3232 KOTA KINABALU

Side road (dip 45°, 5 years old) sandstone: slightly weathered SSPC stability: Sandstone: stable (92%) Shale: unstable (< 5%)

(after Tating et al., 2012)

Weathering influence on engineering structures - Hack 30/10/2012 33 KOTA KINABALU

Main road (dip 30°, 10 years old): sandstone: moderately weathered SSPC stability: Sandstone: stable (95%) Shale: ravelling (<5%)

(after Tating et al., 2012) 10 years old

Weathering influence on engineering structures - Hack 30/10/2012 34 KOTA KINABALU

time dip SSPC visual [years] [degre es] unit RM friction RM cohesion [degrees] [kPa] shale slightly 5 45 4 2.4 instable moderately 10 30 2 1.1 instable

sandstone slightly 5 45 20 10.0 stable moderately 10 30 11 6.3 stable

Weathering influence on engineering structures - Hack 30/10/2012 35 SSPC system in combination with degradation forecasts gives:

. reasonable design for slope stability . with minimum of work and . in a short time . (likely a reasonable tool to forecast susceptibility to weathering)

Weathering influence on engineering structures - Hack 30/10/2012 36 REFERENCES

. De Mulder, E.J.F., Hack, H.R.G.K., Van Ree, C.C.D.F., 2012. Sustainable Development and Management of the Shallow Subsurface. The Geological Society, London. ISBN: 978-1-86239-343-1. p. 192. . Hack, H.R.G.K., 2002. An evaluation of slope stability classification; Keynote lecture. In: Dinis Da Gama, C., Ribeira E Sousa, L. (Eds) ISRM EUROCK 2002, Funchal, Madeira, Portugal. Sociedade Portuguesa de Geotecnia, Av. do Brasil, 101, 1700-066 Lisboa, Portugal, pp. 3–32. . Hack, H.R.G.K., Price, D.G., Rengers, N., 2003. A new approach to rock slope stability : a probability classification SSPC. Bulletin of Engineering and the Environment. 62 (2). DOI: 10.1007/s10064-002-0155-4. pp. 167-184. . Hack, H.R.G.K., Price, D., Rengers, N., 2005. Una nueva aproximación a la clasificación probabilística de estabilidad de taludes (SSPC). In: Proyectos, U.D., Minas, E.T.S.I. (Eds), Ingeniería del terreno : ingeoter 5 : capítulo 6. Universidad Politécnica de Madrid, Madrid. ISBN: 84-96140-14-8. p. 418. (in Spanish) . Huisman, M., Hack, H.R.G.K., Nieuwenhuis, J.D., 2006. Predicting Rock Mass Decay in Engineering Lifetimes: The Influence of Slope Aspect and Climate. Environmental & Engineering Geoscience. 12 (1). DOI: 10.2113/12.1.39. pp. 39-51. . Moreira-Nordemann, L.M., 1980. Use of 234U/238U disequilibrium in measuring chemical weathering rate of rocks. Geochimica et Cosmochimica Acta. 44 (1). DOI: 10.1016/0016-7037(80)90180-5. pp. 103-108. . Olvmo, M., 2010. Review of denudation processes and quantification of weathering and erosion rates at a 0.1 to 1 Ma time scale; Technical Report TR-09-18. Svensk Kärnbränslehantering AB; Swedish Nuclear Fuel and Waste Management Co, Stockholm, Sweden. p. 56. . Price, D.G., De Freitas, M.H., Hack, H.R.G.K., Higginbottom, I.E., Knill, J.L., Maurenbrecher, M., 2009. Engineering geology : principles and practice. De Freitas, M.H. (Ed.). Springer-Verlag, Berlin, Heidelberg. ISBN: 978-3-540-29249-4. p. 450. . White, A.F., Blum, A.E., Schulz, M.S., Vivit, D.V., Stonestrom, D.A., Larsen, M., Murphy, S.F., Eberl, D., 1998. Chemical Weathering in a Tropical Watershed, Luquillo Mountains, Puerto Rico: I. Long-Term Versus Short-Term Weathering Fluxes. Geochimica et Cosmochimica Acta. 62 (2). DOI: 10.1016/s0016-7037(97)00335-9. pp. 209-226.

Weathering influence on engineering structures - Hack 30/10/2012 37