CT3330 Hydraulic Structures Caissons Lecture notes version February 2011 M.Z. Voorendt, W.F. Molenaar, K.G. Bezuyen Hydraulic Structures Caissons Department of Hydraulic Engineering 2 CT3330 Faculty of Civil Engineering Delft University of Technology Hydraulic Structures Caissons TABLE OF CONTENTS PREFACE......................................................................................................................................................5 READER TO THESE LECTURE NOTES .....................................................................................................5 1. Introduction to caissons.........................................................................................................................7 1.1 Definition ..............................................................................................................................................7 1.2 Types ...................................................................................................................................................7 1.2.1 Standard caisson...........................................................................................................................7 1.2.2 Pneumatic caisson ........................................................................................................................7 1.3 Final positions of caissons / where caissons end up ...........................................................................8 1.4 Functions..............................................................................................................................................9 1.5 Construction of a standard caisson......................................................................................................9 2. Caissons through the ages ..................................................................................................................10 2.1 Ancient times......................................................................................................................................10 2.2 Twentieth century...............................................................................................................................12 2.3 Nowadays use of caissons - special applications ..............................................................................17 3. Construction of standard caissons .....................................................................................................21 Intermezzo 1: over-all closure procedure.................................................................................................21 3.1 Prefabrication.....................................................................................................................................22 3.2 Transport............................................................................................................................................23 3.3 Positioning and Immersion.................................................................................................................25 3.3.1 Bed preparation...........................................................................................................................25 Intermezzo 2: preparation of the foundation ............................................................................................25 3.3.2 Positioning ...................................................................................................................................27 3.3.3 Immersion....................................................................................................................................29 Intermezzo 3: sluice caissons ..................................................................................................................30 3.3.4 Ballasting .....................................................................................................................................30 3.4 Finishing the structure as a whole......................................................................................................31 3.5 Maintenance and control....................................................................................................................31 3.6 Final stage..........................................................................................................................................31 4. Design of standard caissons................................................................................................................32 4.1 Design method...................................................................................................................................32 4.2 Determination of the main dimensions...............................................................................................33 4.2.1 Height ..........................................................................................................................................33 Intermezzo 4: reduction of the wave load on vertical breakwaters ..........................................................35 4.2.2 Width ...........................................................................................................................................36 4.2.3 Length..........................................................................................................................................36 4.2.4 Thickness of the concrete elements............................................................................................37 4.2.5 Draught........................................................................................................................................38 4.3 Design checks....................................................................................................................................38 4.3.1 Static stability of caissons (during transport and immersion) ......................................................38 4.3.2 Dynamic stability of floating caissons..........................................................................................39 4.3.3 Shear criterion caisson-subsoil ...................................................................................................39 4.3.4 Rotational stability........................................................................................................................40 4.3.5 Vertical bearing capacity .............................................................................................................41 4.3.6 Piping and scour..........................................................................................................................41 4.3.7 Strength of the reinforced concrete structure..............................................................................42 4.4 Example 'hand calculation' standard caisson ....................................................................................44 4.4.1 Situation and hydraulic boundary conditions ...............................................................................44 4.4.2 Phase I: Caisson in building dock ...............................................................................................45 4.4.3 Phase IIa: Floating caisson – estimating the main dimensions...................................................45 4.4.4 Phase IIa: floating caisson - strength check................................................................................46 4.4.5 Phase IIa: floating caisson - static stability..................................................................................48 4.4.6 Phase IIa: floating caisson - dynamic stability.............................................................................49 4.4.7 Phase IIb: immersing caisson - static stability.............................................................................50 Department of Hydraulic Engineering 3 CT3330 Faculty of Civil Engineering Delft University of Technology Hydraulic Structures Caissons 4.4.8 Phase III: just immersed caisson - only ballasted with water ......................................................51 4.4.9 Phase III: caisson fully ballasted with sand - shear criterion .......................................................52 4.4.10 Phase III: caisson fully ballasted with sand - turn-over criterion................................................52 4.4.11 Phase III: caisson fully ballasted with sand - bearing capacity subsoil......................................52 4.4.12 Phase IV: operational phase .....................................................................................................54 4.4.13 Phase V: removal phase ...........................................................................................................54 4.4.14 Conclusion of this example design............................................................................................54 5. Construction of pneumatic caissons ..................................................................................................55 5.1 Preparation.........................................................................................................................................55 5.2 Caisson construction..........................................................................................................................55 5.3 Subsidence ........................................................................................................................................55 LITERATURE, REFERENCES ...................................................................................................................59