The SIMBAT technique was developed by a French geotechnical engineer called Paquet in the 1980’s. Since when, the method has been developed further and has gained in popularity over traditional
dynamic testing techniques.
The core differences are:
- A high speed optical/digital theodolite is used to record real time displacement.
- A series of high and low strain blows are used, so static reaction to be determined without assuming soil damping factors
- Displacement data from the theodolite is used to correct accelerometer data
- Simulation model is based on accurate displacement, rather than calculated velocity
These differences mean that SIMBAT has been independently rated the most accurate high strain dynamic testing method available. The method is commonly used
on both pre-cast and cast in place piles to determine performance.
Features
- Unique Theodolite measures elastic and permanent displacement remotely
- Rugged handheld acquisition unit, weighs less than 2Kg
- Storage for over 700 results
- Instant Dynamic Reaction and Displacement readings
- Backlight LCD screen for working in dark environments
- Simulation software for analysis of pile shaft and end bearing resistance
- Load/Settlement plot output
- Battery powered system
- Suitable for both cast in place and pre-cast piles
Software
The SIMBAT analysis software is supplied as standard. It is Windows based and user friendly. Modules enable you to calculate the impedance of the pile test cap and pile shaft separately and analyse each blow individually to determine dynamic reaction and displacement.. The software can present results in tabular format, as well as presenting the separation of forces curves and the predicted static load settlement plot.
An integral part of the SIMBAT software is a numerical simulation, whereby experimental signals are introduced into the programme and compared with theoretically generated signals. Skin friction and end bearing components of the pile/soil system can then be derived.
Specifications
|
Acquisition Unit
|
|
| Acquisition: |
4 channel, 16 bit acquisition at 10Khz sample rate. Pre-trigger, auto gain and auto balancing of strain gauges. |
| Storage: |
700+ results, including 3 data sets per pile with full header information; site, pile no, diameter, operator, transducers and date/time stamp. |
| Keypad: |
Sealed colour coded and full alphanumeric keypad, tactile and audio feedback |
| Operating Temperature: |
0 to 50 Deg C |
| Size: |
L 218 x W 187 x D 55mm |
| Weight: |
1.35Kg |
| Display: |
Monochrome LCD Transflective with backlight. Contrast keypad adjustable. Display area 122 x 70mm. Protective anti-reflective glass. |
| Backlight: |
Backlit display with auto-off |
| Connectors: |
Waterproof Lemo type, each with unique configuration. |
| Power: |
Battery: 1.2V NiMH rechargeable "AA” cells Battery Life: 8hrs+ operation on full charge Battery Charge Time: Approx 6Hr |
| Charger: |
External wall plug-in charger for 100/110/250VAC inputs. External cigar plug -in charger for 12VDC inputs |
|
Theodolite
|
| Theodolite |
High speed optical theodolite with laser targeting and halogen target illumination. |
| Battery: |
NiMH rechargeable - 6hrs + |
| Charger: |
External wall plug-in charger for 100/110/250VAC inputs. External cigar plug-in charger for 12VDC inputs |
| Accuracy: |
0.14mm @ 5m |
| |
Sensors |
| Accelerometers: |
2No 5000g ‘shock’ type with ICP power supply.
|
| Strain Gauges: |
60mm foil type for accurate measurements. |
| Calibration: |
both accelerometers and the theodolite supplied are calibrated, using reference equipment traceable to UK national standards (UKAS). |
| Standard Supply Includes: |
Simbat Acquisition Unit, Simbat, 2 No PCB Accelerometers, Theodolite cable reel, acquisition connection box, acquisition box cable reel, accelerometer connection cables, strain gauge connection cables, 10 No
strain gauges, fixing kit including target, Data transfer cable, AC Adapter charger for unit and theodolite, DC Charger lead for unit, Waterproof carry cases for unit and theodolite, Protective pouch with neck strap, Instruction Manual, Simbat Software CD, Calibration certificates, 1 Year Limited Warranty |
Simbat Software
The Simbat software is an easy to use Windows based platform for analysing results and producing reports. Typical plots are shown to the right. All modules including the simulation module are included as standard.
Methodology
The method is based on the propagation of waves in long elastic cylinders. When the pile top is struck with the falling weight the pile section is deformed (enlarged) and this enlargement travels down the pile to the toe where it is reflected back up. In a free, un-damped piles the particle velocity of the return wave would be identical to the original wave.
When the pile is surrounded and restrained by soil, part of the wave is reflected back up at each and every external restraint, the remainder of the wave continues downwards. So at any one time there are both upwards and downwards forces and velocities in the pile.
The SIMBAT technique is able to separate these upwards and downwards forces, F (up) and F (down) and calculate dynamic soil reaction, Rdy, as the difference between the upwards force in a free pile and the real upwards force measured. The conversion of dynamic to static reaction is carried out by expressing Rdy as:
Rdy=R STAT + (K.ep)a
Where:
ep = permanent penetration.
K = a parameter which is a function of the pile and the sequence of the blow.
a = a parameter which is a function of the soil.
