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The Seismic Dilatometer test (SDMT) in geotechnical inshore and offshore investigation www.marchetti-dmt.itStudio Prof Marchetti.

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Presentation on theme: "The Seismic Dilatometer test (SDMT) in geotechnical inshore and offshore investigation www.marchetti-dmt.itStudio Prof Marchetti."— Presentation transcript:

1 The Seismic Dilatometer test (SDMT) in geotechnical inshore and offshore investigation www.marchetti-dmt.itStudio Prof Marchetti

2 Some examples of maritime construction Trench for pipe Sheet piles Oil and gas platform Wind generators Mooring

3 Common tests in offshore investigation Close water (harbours and bays) - inshore tests Open water (sea) - offshore tests Short test (5 m) - cables - pipes Deep test (30 m) - foundations Shallow water < 30 m Short test (5 m) Deep test (30 m) Deep water > 30 m

4 Harbour: DMT test from pier Steps Make a hole in the deck; Set up the guidepipe; Fix the penetrometer and do the test; La Spezia (Italy) Shipyard Beconcini Guidepipe Pier Seabed

5 Harbour: DMT test from provisional pier Salerno harbour (Italy) Trapezio Deck Beam braching

6 DMT test with Floating Wheels Module Two ton static penetrometer mounted on a floating raft, with screws for anchoring. Only for very shallow water: 1-2 m; Short test: 5 m

7 DMT with SPT hammer for shallow water: Costa Rica

8 Rig Jackup DMT test with Torpedo - layout SEABED SEA LEVEL

9 DMT test from Jack-up Venice lagoon, Italy (MO.SE.) Vado Ligure, Italy New embankement area

10 SDMT tests from a floating barge

11 SDMT test from a floating barge: layout Test execution Barge is free to float. The upper end of the telescopic pipe is fixed on the pontoon, the lower end is on the seabed. It is a guide for the dilatometer rods. The operator pushes the rods carefully during floatation. When the prefixed depth is reached, the operator stops the pushing system, disconnects rods and starts to take the DMT readings. All the reading are taken when the DMT is fixed, not during penetration.

12 SDMT from a floating barge: Genova (Italy) New Terminal Container – Calata Bettolo (Genova Horbour)

13 DMT from a pontoon : pushing phase

14 DMT from a pontoon : reading phase

15 Jackup vs Floating Barge: cost comparison 10 days rental 300.000 10 days rental 10.000 In 10 days you save 290.000

16 DMT from floatinf barge and jackup: Barcelona (ES) Enlargment Barcelona harbour – collapse of the pier

17 DMT test with torpedo in deep water: layout DMT test for seabed < 100 m of depth; Test depth: 30-40 m; Expensive heave compensated ship for offshore test

18 Seafloor DMT for shallow water Test depth: 5-7 m Pontoon

19 Seafloor DMT in deep water Ok using any vessel with at least 2 ton crane Limitation: Max seabed depth: 100m (due to DMT cable) Test depth: 5-7 m

20 What about DMT tests at depth > 100 m ? No pneumatic cable between vessel and DMT MEDUSA PROJECT

21 Medusa Project Elettronic Board Pressure Transducer Pressure Generator Designed for seabed up to 2000m

22 Summary and Conclusions - Same blade for offshore and onshore sites - No calibration necessary for the (high) pore pressure - DMT test is independent from the method and speed of penetration (same high quality data using many different penetration methods) - Test is rapid and economical if performed with a penetrometer on a floating barge - Today SDMT tests are possible up to 100m (using expensive vessels)

23 In the near future.. The seafloor DMT will allow to perform shallow tests (5-7 m depth) with a seabed up to 100 m. The test will be very economical because it may be performed using a common vessel with a little crane (2 ton) The Medusa DMT will allow to perform DMT tests up to the depth of 2000 m


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