Washington D.C. 2nd-4th April 2006 D M T 2006 Washington D.C. 2nd-4th April 2006

WIRE-LINE MEDUSA Electronic DMT for great depth

Drilling and coring Coring and casing -sketch- For shallow continuous coring bore-holes the commoniest method is using the “simple tube core barrel” As the name says it is a simple tube (commonly its length varying from 1,5 to 3 m) which is pushed into the soil by the drill rig. Depending on the type (loose, soft, cohesive, etc) of soil (i.e. clay, sand, gravel) the core barrel is simply pushed, pushed and rotated, sometimes hammered or also pushed by vibrating it. If the soil collapses (almost always) the hole is cased with the casing drillstrings.Therefore the commoniest method to perform continuous coring bore holes is an alternance of coring with the core barrel and casing the previously cored length of the hole, as shown in the following picture: Coring and casing -sketch- C= coring R= casing THE CORE BARREL IS ALWAYS DRIVEN BY RODS WHICH ARE SCREWED AND UNSCREWED EVERYTIME STANDARD METHOD

Advantages and disadvantages of using rods and casing Simplicity of use “idiot-proof” operations low cost of the drilling tools No special requirements for water/mud pumps Fast installation of the drill rig DISADVANTAGES: Poor quality of the cores (the friction with the inside walls of the core barrel sometimes causes burning and cementation of the core) Very often : poor recovery (expecially in loose soils) Very slow operations by increasing the depth: the more is the depth the more rods have to be screwed (to lower down the core barrel) and unscrewed (to retrieve the core barrel) Much more “hand-power” required (for screwing/unscrewing the rods hundreds times per day) Much more power required to the drill rig, expecially for the casing

WIRE-LINE The “recovery by cable or wire” system (hence the name “wire-line”) is based on the use of a core barrel which, integrated with the casing, makes a sole body. Pushing and rotation are conveyed by the same casing. The system is essentially made up of: Drilling rods (or "casing") inside which, at the bottom terminal part, there is an element (usually a slot) where the core barrel is lowered down by the wire and takes place inside, so allowing the drilling rods to rotate and push. Core barrel or drilling tool: this is placed inside (throughout the interior of) the drilling rods and has a hook-up system.

WIRE-LINE Hooking system And Overshot Mud pools in WL installation

WIRE-LINE NOT A SINGLE ROD IS SCREWED/UNSCREWED FOR LOWERING AND RECOVERING THE CORE-BARREL ONLY THE “CASING” RODS ARE SCREWED ONCE FOR DRILLING AND UNSCREWED ONCE FOR RETRIEVING NO HAND-POWER REQUIRED -IT IS COMPLIANT TO ALL SAFETY REQUIREMENTS-

WIRE-LINE details HOOKING SYSTEM Casing = drill rods Internal core-barrel OR no-coring assemply OR Sampler OR special tool (medusa, CPT, etc) The INTERNAL CORE-BARREL can be rotating Or not rotating (having bearings under the Hooking system preventing from rotation) Water/mud flowing

WIRE-LINE drill rig BASICALLY THE DRILL RIG APPLIES “ENERGY” TO THE CASING RODS IN FORM OF TORQUE (for rotation) THRUST (for pushing and pulling) AND WATER/MUD PRESSURE (for “cutting” the Soil and lift the cuttings up)

Lowering CB

Lowering CB

hooking HOOKING (the corebarrel Latches inside The rods)

CORING ROTATION PUSHING WATER/MUD INJECTION

END OF CORING

INSERTING THE OVERSHOT

wire LOWERING THE OVERSHOT

UNLATCHING THE COREBARREL

Lifting the CB up

Lifting the CB up

Lifting the CB up

Recovering the cb

ADVANTAGES OF WIRE-LINE NEARSHORE/OFFSHORE GEOTECHNICAL SURVEYS C P T W D: CONE PENETRATION TEST WHILE DRILLING (uses wire-line)

ADVANTAGES OF WIRE-LINE Quality speed of execution almost independent from depth Flexibility (wide choice of tools can be used: corebarrels, special tools, no-coring assembly, etc) The hole is ALWAYS cased Much less “horsepowers” are required to the drill rig (the casing is always rotating, no great friction outside the casing rods) SAFETY No “hand-power” is required, the Operators are not so much stressed Can be used in ALL type of soils (it was born for rock coring)

DISADVANTAGES OF WIRE-LINE It is much more complicated than the “simple core + rods” method it must be used ONLY by very-skilled (and smart) Operators The installation of the drill rig is very slow, more or less same time is required for a 15 m or 150 m deep bore-hole! The drilling tools are much more expensive, so as the mud-pumps, pools, etc it is not raccomandable for shallow “environmental” surveys, because there is water/mud circulation (it might cause cross contamination)

MEDUSA Nothing to deal with jellyfish, but the way of moving looks like it Basically is a standard dilatometer (in terms of sizes and principle of functioning); differently from the standard equipment it is managed electronically and the bottle of nitrogen is contained inside a special wire-line “core-barrel”. No tools are placed in the surface, no manometers, no bottle; just a laptop, in order to download data and show on the screen the operations It is used inside a standard wire-line, whose outer diameter is 130 mm. Same wire-line can be used for continuous coring, sampling, no coring (with or without MWD), CPTWD.

“core barrel” and Hooking system Nitrogen bottle GENERAL VIEW OF MEDUSA (underground) electronics 50 mm diameter rods DMT blade

General view of the system (above the ground)

Photo # 1 Wire-line Casing rods DMT

Photo # 2 Internal Core barrel Protruding Rods and DMT

The Medusa equipment functions as follow: Inside the wireline casing rods is lowered the “core-barrel” containing the bottle of nitrogen, the electronics, and having the DMT protruding 1,6-3,2 m (the lenght depending on some factors, such as (but not only): soil stiffness, thrust power of the drill rig, swelling or collapsing of the bottom of the hole, etc); prior of lowering it there is a synchronisation between the laptop and the electronics of Medusa. It is programmed the test (DEPTH, TIMES, ect) Once lowered the medusa core-barrel latches into the casing rods The operator knows that he must push the rods according to certain steps (pre-programmed rate of penetration) and stop the medusa every 20 cm of penetration; IN THE LAPTOP IS SHOWN EXACTLY HOW THE MEDUSA IS MOVING ACCORDING TO THE TEST AS PROGRAMMED

Electronics, synchronisation The electronics manages the bottle with a valve in such a way to enflate and deflate the membrane (exactly as the standard DMT) A pressure sensor detects the A and B values The values (time, A, B) are memorised into the internal RAM During the testing the laptop shows to the Operator how the medusa is moving Once the corebarrel is lowered and the “brain” is connected again to the laptop The software dowloads the A, B values

BASIC OPERATIONS Electronics (microcomputer Inside the Corebarrel) Prior to any pushing it has to be done the SETTING of the Medusa: refilling/controlling the pressure of the nitrogen bottle Control the DMT and the membrane connecting the electronics to the laptop PROGRAM THE TEST Electronics (microcomputer Inside the Corebarrel) valve LAPTOP

SCREEN OF THE LAPTOP DURING THE TESTING Time to Push:01:30 Making: A

Step 1 Drilling to depth -100 m by using one of the following methods: -no coring drilling (with or without MWD) -continuous core -CPTWD -sampling or testing -100

Step 2 -98,40 Lifting the rods up to -98,50 m And recovering the drilling tool. The hole is always filled with water+bentonite and/or polymers Water+bentonite filling

Step 3 -98,40 -100,00 Inserting the Medusa Core Barrel and latching it Into the rods Prior to the inserting the microcomputer inside the corebarrel is Resetted and the synchronisation with depth is done -98,40 N.B. the lenght of the rods protruding Out the bottom of the drilling rods Should be a multiple of 20 cm, normally varying From 80 to 320 cm, in this case is 160 cm -100,00

Pushing the medusa into the soil, with 20 cm steps. After each interval (20 cm) the pushing is stopped for a certain Time interval, allowing the DMT test to be done Step 4 -100,20……-101,60

END OF PUSHING Step 5 a -100

Step 5 B END OF PUSHING And recovering the medusa Core Barrel Remoulded soil

Step 6 INSERTING A CONTINUOUS CORE BARREL AND CORING THE REMOULDED SOIL FOR CALIBRATION WITH THE DMT RESULTS Remoulded soil

NEW WAY OF DMT TESTING WL MEDUSA WILL ALLOW TO ACHIEVE DMT DATA AT A GREATER DEPTH with no need to drill with rods (therefore in much less time) THE INTERPRETATION OF THE DATA IS AS PER THE STANDARD The tested ground can be cored so to have a “qualitative” evaluation The results are again “not sensitive” to the method of pushing

POSSIBILE FIELDS OF APPLICATION OF MEDUSA TECHNOLOGY Offhore drilling: the possibility to obtain DMT data without using a static penetrometer on a barge together with the drill rig allows less costs and more reliable data at the same time. Testing in sites where the penetrometer is not usable (i.e. shallow gravel and then clay or silt/sand) Testing inside a bore-hole instead of using other unreliable and sometimes expensive kind of test

THANK YOU The WL Medusa has been projected by: Prof.Silvano Marchetti Mr.Diego Marchetti -Engineer- Mr.Massimo Sacchetto Engineer- THANK YOU