SAFETY PERFORMANCE OF DAMS IN CHILE’S HIGHLY SEISMIC ENVIRONMENT


Visual inspection indicated a longitudinal crack along the crest, 10-20mm in width and 100cm long. Also, a transversal crack near the left abutment and another in the contact with the spillway. None of the cracks were too deep. No variation on Casagrande piezometers were detected, as well as no changes in infiltration flows.


Surface monitors indicated a settlement of 7.1cm at the centre of the dam, diminishing to 20% of that value near the abutments.


La Paloma dam is located approximately 25km to the south-east of Ovalle City, with a reservoir capacity of 740Mm3. The dam was constructed between 1959 and 1967. It has a maximum height of 82m, and a length of 1000m (including a 100m wide spillway in the left abutment). It is a zoned dam with a clay core and shoulders constituted by borrow materials, as observed in the cross-section of Figure 24. It is founded in old fluvial gravelly material of variable thickness; however, part of the right abutment is directly supported by bedrock (see Figure 24). The irregular foundation ground has been the cause of non-homogeneous settlements; however, Paloma dam has shown good seismic behaviour, with only minor damage after the Punitaqui and Illapel earthquakes.


Figure 24. Cross-section and longitudinal section of Paloma Dam


Colbún dam is a zoned earth dam 116m high and 550m long. It has an inclined sandy clay core and compacted gravel shells. It is founded in a fluvial deposit, 68m thick. A concrete cut-off wall was built through the fluvial deposit to control seepage. During the Maule earthquake of 2010, an accelerograph in a rock tunnel next to the dam registered a peak horizontal acceleration of 0.37g. The registered peak vertical acceleration was 50% over the horizontal acceleration. It has been informed[20,24] that this dam, the highest earth dam for water retaining purposes in Chile, suffered only minor damage during the earthquake and relatively low settlements and displacements of no more than 10cm. Transverse cracks across the crest next to both abutments had a thickness of 1cm, and when excavated disappeared at a depth of 3m.


An electrical conduit next to the downstream edge of the crest was displaced by a maximum


of 2m horizontally and almost 1m vertically, but inclinometers along the downstream shoulder did not show any deformations after the earthquake.


Vol XXXI Issue 3


DAM ENGINEERING


207


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