Load measurements at riprap toe.

iii ACKNOWLEDGEMENT . v LIST OF FIGURES . viii LIST OF TABLES . x 1.0 INTRODUCTION . 11 1.1 Background . 11 1.2 Research Objectives . 13 1.3 Thesis Outline . 14 2.0 LITERATURE REVIEW . 16 2.1 Riprap as Slope Protection . 16 2.2 Riprap Design at Embankment Dam Toe . 19 2.3 Load Measurements . 21 3.0 EXPERIMENTAL SETUP AND PROCEDURE . 23 3.1 Research Instrumentation and Setup . 23 3.2 Experimental Procedure . 26 4.0 RIPRAP STONE MEASUREMENTS . 30 5.0 RIPRAP BUILDING LOADS . 31 5.1 Load Profile at Riprap Toe during Riprap Construction . 31 5.2 Load Resolutions at Riprap Toe. 33 6.0 OVERTOPPING TESTS RESULTS . 35 6.1 Load Profile at Riprap Toe . 36 6.2 Riprap Failure . 39 6.3 Effects of Loading on Riprap Behavior . 42 7.0 CONCLUDING SUMMARY AND RECOMMENDATIONS . 48 REFERENCES . 50 APPENDICES APPENDIX 1: TEST 2 . 52 APPENDIX 2: TEST 3 . 55 APPENDIX 3: TEST 4 . 58 APPENDIX 4: TEST 5 . 61 APPENDIX 5: TEST 6 . 64 APPENDIX 6: TEST 7 . 67 Load Measurement at Riprap Toe. vii APPENDIX 7: TEST 8 . 70 APPENDIX 8: TEST 9 . 73 APPENDIX 9: TEST 10 . 76 APPENDIX 10: RIPRAP STONE MEASUREMENTS . 79 Load Measurement at Riprap Toe. viii LIST OF FIGURES Figure 1 Illustration of flow concentration at the toe of an embankment dam under overflow and or throughflow scenarios. 12 Figure 2 Laboratory model test which shows highly turbulent flow condition at the riprap toe on the downstream slope of an embankment dam. Photo by K.N. Opare . 13 Figure 3 Possible failure scenarios of protection layers on overtoppable earthdams as depicted by Siebel 2007. 18 Figure 4 Siebel 2007's illustration of slope protection layer on rollers with attached load cells for the experiment on sliding. 21 Figure 5 General plan and section of the test flume in the hydraulics laboratory at NTNU as illustrated by (Pattersen,2015). 23 Figure 6 Test set-up for experiments with placed riprap as used by (Hiller et. al., 2017) . 24 Figure 7 Modified test set-up with load cells incorporated at the riprap base and a shortened chute length from 1800mm to 1750mm used for this current experiment. 24 Figure 8 The S9M load cells used for the experiments. 25 Figure 9 Sketch showing the various components of the load cell for the various nominal rates as depicted by HBM. 26 Figure 10 Illustration of stone axes from (Bunte and Abt, 2001). 27 Figure 11 Constructed riprap ready for overtopping test with marked stones at specified distance from the toe for observing displacements. View from both upstream and downstream. View from downstream also shows installed load cells. Photos by K.N. Opare. 28 Figure 12 Progress of riprap stone self-weight on the dam toe as recorded during riprap construction for all tests. It is seen how the load stabilizes after a threshold distance from the toe. 31 Figure 13 Scattered riprap building load profile for all tests to find the threshold distance at which the building load stabilizes. 32 Figure 14 Force resolutions within a section of the riprap layer. 33 Figure 15 Graph of critical discharges against packing factors for all overtopping tests which shows no linear relation. 35 Load Measurement at Riprap Toe. ix Figure 16 Typical load generation profile for an overtopping test obtained from the load cells with all six individual readings and then a summed up total reading for all the cells combined (Test 2). 36 Figure 18 Two different overtopping scenarios during tests. Low discharge resulting in highly aerated flow over the entire riprap on the left and high discharge resulting in a complete clearly defined depth of water over the riprap layer on the right. 38 Figure 19 Removal of a single stone after one of the overtopping tests. Entire riprap structure worked perfectly even with that stone removed. 39 Figure 20 Observed 2D displacement of the six marked stones for showing buckling-like pattern of riprap for all tests combined. 41 Figure 21 Overtopping test with clear separation between riprap layer and the underlying filter layer which shows how the riprap has unstabilized with the 2D deformation resembling buckling. 42 Figure 22 Graphs showing the x-direction displacements of marked stones against the recorded compaction effect load with a linear fit for all tests.