Kanji_edit.qxp 1/7/09 4:17 pm Page 28
Debris Flows at Cubatão Oil Refinery, Brazil
Refining Assets
a report by
Milton Assis Kanji, Faiçal Massad and Paulo Teixeira da Cruz
Polytechnical School, University of São Paulo
The Cubatão Oil Refinery of Petrobrás is located at the foot of an some of them catastrophic and with more than 100 deaths. An account
800m-high mountain range that runs parallel to the south-eastern of these occurrences is given by Gramani and Kanji.
1
Brazilian coast. The site was chosen in the 1950s, at the beginning of
a period of rapid industrial development in the country, and was The Debris Flow Event
planned to host several industries related to oil subproducts. The site On 4 February 1994, after an intense rainfall, the refinery was struck by
was selected due to its topographical characteristic of flat lands, a heavy debris flow that occurred along the creeks located at the hill
its location close to the port of Santos – the largest port in Latin slopes behind the refinery. The rainfall had an intensity of 60mm in one
America – and because it is served by railroads and highways, hour, which caused about 100 landslides on the hill slopes within the
considered to be optimum strategic conditions. basins behind the refinery. The debris flow, consisting of a mass of mud,
stones and boulders, plus trees, wood logs and branches, travelled
The Cubatão Refinery, officially called Refinaria Presidente Bernardes down the hill slopes at a velocity that reached 50–60km/h, causing great
Cubatão, is an important unit for Petrobrás, mainly as it is the destruction to several utilities on its way. It destroyed seven low gabion
company’s most complex site, producing a wide variety of products. Its dams (built by Petrobrás after a super-concentrated flow due to heavy
production rate is about 200,000 barrels per day. rains in 1985) and damaged fire water pipes (see Figure 1) and
protection dykes, leading to invasion of tanking areas (see Figure 2). The
The flat area of the refinery is covered by recent deposits, either mass encountered a water reservoir at the foot of the hill, used to store
alluvium (from river sediments or debris flows) or colluvium (from the and supply industrial and fire water to the refinery, where a large
closer hillsides), or even marine sediments at elevations less than about amount of trees and branches completely clogged its spillway, causing
7m. As a consequence, some foundation and hill slope stability an overflow of the liquid mass. As a result, the industrial plant area was
problems have arisen. Many and varied solutions have been employed flooded with about 1m of mud and stones (see Figure 3), causing the
in these industries according to their location and geology. interruption of its operation for about two weeks until the area was
completely cleaned. The volume of muck removed (saturated soil and
The mountain range is called Serra do Mar, and generally ranges between stones) was about 300,000m
3
, estimated from the number of trucks
700 and 1,000m. However, it is steep, with an average inclination of some involved in these works. This large accident resulted in 10 days of no oil
30º. Since the weather is tropical and humid, with occasional heavy and production at a cost of about US$44 million.
intense rains, there have been occurrences of generalised landslides and
debris flows at several points along the mountain range in the recent past, Studies of Solutions
Although other debris flows had already occurred in the region, there
was not enough experience in the country with respect to remedial
Milton Assis Kanji is an Associate Professor at the
Polytechnical School of the University of São Paulo,
and protective measures against this type of phenomenon. For this
where he works on geotechnical engineering and rock
reason, Petrobrás sought the help of the Polytechnical School of the
mechanics. He is also Chairman of the International
University of São Paulo. A core multidisciplinary team of six experts
Joint Technical Committee on Soft Rocks.
was set up, dedicated to the study of the event and understanding the
E: milton.kanji@gmail.com
triggering and transport mechanisms of debris flows in order to
acquire information about the required parameters for the design of
Faiçal Massad is a Professor and a Geotechnical
protection works.
Consultant at the Polytechnical School of the University
of São Paulo, where he works in the fields of soil
Some emergency works were recommended at the very beginning, such
mechanics, foundation engineering and earthworks. He
has authored 135 technical papers, some of them
as a protection dyke and lowering the crest of the existing spillway,
related to landslides and debris flows. Professor
which proved very useful: a minor debris flow occurred in 1996, but
Massad obtained his MSc from Harvard University.
there were no consequences thanks to the effect of these works.
Paulo Teixeira da Cruz is an Assistant Professor at the The core group also visited similar works in Japan and Austria to learn
Polytechnical School of the University of São Paulo,
about different approaches to the problem, which was very useful as
where he works on dam engineering and earth dams.
He has published over 100 papers, mainly related to
the best concepts from these two locations were utilised. Another
earth dams, and has published two books on dam
important activity was a back analysis of the 1994 and 1996 events,
engineering. Professor Teixeira da Cruz gained his MSc
in geotechnical engineering from the Massachusetts
with complete inspections of the site, field grain size analysis of a 4m
3
Institute of Technology (MIT). sample and calculations. A full account of the analysis was presented by
Massad et al.
2,3
and Kanji et al.
4
28
© TOUCH BRIEFINGS 2009
Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108