TECHNOLOGIES
LASERSCAN
For many as-built and topographic surveys, laser scanners have already proven to significantly reduce field labor compared to traditional methods.
RODAR
The RODAR® system, can be used to study different types of constructions, interiors, and underground structures.
RESISTIVITY IMAGING
The Resistivity Imaging method is especially valuable in areas where ground penetrating radar (GPR) methods do not work because of conductive overburden.
FALLING WEIGHT DEFLECTOMETER
A falling weight deflectometer, FWD, is a testing device used by civil engineers to evaluate the physical properties of a pavement.
DYNAMIC CONE PENETROMETER
For surveying purposes in subgrade structures, the Dynamic Cone Penetrometer (DCP) is a technology which analyzes through a series of in-situ tests, the load bearing capacity of the base and sub-base layers.
RODAR
The RODAR® system, can be used to study different types of constructions, interiors, and underground structures. It has the capability of locating underground installations, measuring humidity, finding milimetric cracks, holes and caverns under the surface along with other applications.
The Ground Penetrating Radar consists of the transmission of pulses of energy, and the time delay of its reflection from an object is used to calculate the distance to that object. Short pulse radar works on the same principle as that used for locating storms, aircraft and ships, except that the range of the reflecting object is very short. The correspondingly short delay time requires an entirely different design for the electronics used in both the transmitter and receiver. Depending on the dielectric value, the wave velocity varies for different materials and these variations are analyzed by the software resulting in a vertical section which identifies the thickness of the materials and other characteristics.
The original patented short pulse radar system known as RODAR Ground Penetrating Radar (GPR) has been available for several years to provide a subsurface profile of pavement structures and to provide techniques for interpreting the profile to determine the in-service condition of pavement structures. Rodar has the capability to detect layer thickness, void location, deteriorated areas, and excess moisture in the subsurface. The system has been used to evaluate all types of transportation structures including highway, bridge, and airport pavements and tunnels. The purpose of these non-destructive evaluations is to assist in determining maintenance and rehabilitation needs, as well as providing construction quality control. The application of the technology is tailored to the needs of the individual project and to client requirements. A final report can be prepared from the interpreted data. Each report is customized to fit the findings of the survey and the reporting needs of the client. Accompanying the presentation of results is a final report which summarizes data collection, interpretation, results, and recommendations.
LASERSCAN
For many as-built and topographic surveys, laser scanners have already proven to significantly reduce field labor compared to traditional methods.
Field labor is now as little as one-fifth of that of traditional methods for many projects. Infrastructure, sites, small buildings and tall buildings can be cost-effectively surveyed, both inside and out. Digital photos can be overlaid for added realism. With a 10-times boost in maximum instantaneous scan speed and the full freedom and accuracyof a total station, the ScanStation 2 has lifted laser scanning to the next level. This speed and productivity boost builds on the already industry-leading versatility of the ScanStation™ class of laser scanner to make High-Definition Surveying™ (HDS™) profitable for even more as-built and topographic survey projects
Whether you’re designing a modification to a complex refinery piping system, surveying a site or documenting a historic building, you need reliable measurements. High-Definition Surveying scanning systems and software by Leica Geosystems provide you with exact data of what’s there. When your as-built information has to be right, rely on NDT, the company that professionals trust for their scanning solutions. NDT is best known for pioneering scanning technology with trustworthy, total solutions: versatile, accurate laser scanners, industry standard point cloud software, and a full complement of accessories, training and support.
Dramatically faster scanning lets users collect data in tighter time windows, reduces time spent in hazardous locations, provides project results faster.
RESISTIVITY IMAGING
The Resistivity Imaging method is especially valuable in areas where ground penetrating radar (GPR) methods do not work because of conductive overburden. Conductive materials, for example clay, attenuates the radar signal so that no result, or very limited result, can be achieved. In such areas, which are very common in large areas of the world, the resistivity method is the only real alternative for subsurface 2D and 3D mapping of the near surface.
Field procedure is simple. First set out electrode stakes at even intervals. Then lay out the electrode cable and attach each take-out to the stakes. Finally connect the instrument to the electrode cable, perform an automatic test to check that everything is connected correctly and then start the automatic recording. The resistivity measurements are stored directly in the memory of the instrument.
When the field measurement is complete the data are downloaded to a computer, inverted from apparent resistivity into “true” resistivity and presented as a color cross-section of the subsurface. Some of the usual applications for Resistivity Imaging are:
- Geotechnical investigations
- Construction site investigations
- Fracture and cavity detection in bedrock
- Groundwater exploration
- Environmental investigation
- Investigation of dam leakage
- Sand and gravel exploration
- Site characterization for development
- Site investigation for horizontal drilling
- Site investigation for tunneling operation
- Marine image profiling
FALLING WEIGHT DEFLECTOMETER
A falling weight deflectometer, FWD, is a testing device used by civil engineers to evaluate the physical properties of a pavement. This could include (but is not limited to) highways, local roads, airport runways and railway tracks. The machine is usually contained within a trailer that can be either towed to a location by another vehicle or, when used on railway tracks, placed on a hand trolley and pushed to the location.
The FWD is designed to impart a load pulse to the pavement surface which simulates the load produced by a rolling vehicle wheel. The load is produced by dropping a large weight, and transmitted to the pavement through a circular load plate – typically 300mm diameter. A cell mounted on top of the load plate measures the load imparted to the pavement surface.
Deflection sensors (most FWDs use geophones, force-balance seismometers are also used) mounted radially from the center of the load plate measure the deformation of the pavement in response to the load. Some typical offsets are 0mm, 200mm, 300mm, 450mm, 600mm, 900mm, 1200mm 1500mm. The deflections measured at these geophones are termed D0, D200, D300 etc.
FWD data is most often used to calculate stiffness-related parameters of a pavement structure. The process of calculating the elastic moduli of individual layers in a multi-layer system (e.g. asphalt concrete on top of a base course on top of the subgrade) based on surface deflections is known as “backcalculation”, as there is no closed-form solution. Instead, initial moduli are assumed, surface deflections calculated, and then the moduli are adjusted in an iterative fashion to converge on the measured deflections. This process is computationally intensive although quick on modern computers. The FWD data can also be very useful in helping the engineer divide the length of the pavement into homogeneous sections, as well as to calculate the degree of load transfer between adjacent concrete slabs, and to detect voids under slabs.
DYNAMIC CONE PENETROMETER
For surveying purposes in subgrade structures, the Dynamic Cone Penetrometer (DCP) is a technology which analyzes through a series of in-situ tests, the load bearing capacity of the base and sub-base layers. The load bearing capacity is determined by the depth of penetration that consists of a conic tip attached to a rod with a 10 pound weight. This weight falls from a height of 80 centimeters and penetrates the ground. Over a series of tests, a comparison curve is obtained, and certain characteristics of the ground can be analyzed such as compactation grade, and resistance to penetration. The Dynamic Cone Penetrometer allows a real insight of the characteristics of the materials which make up the layers, getting to know the conditions at the moment of the survey.
Depending on the type of ground, the next step is to analyze the limits of consistency which include the following factors:
- liquid limit
- plastic limit
- contraction limit
- humidity content
- specific solid weight to obtain a classification
DCP Advantages:
- Low operation cost
- Almost non-destructive surveying
- Result reliability
The Dynamic Cone Penetrometer (DCP) is a simple and low-cost tool for in-situ ground resistance surveys, and a fast auscultation of the ground layers. It allows a combination of other more known auscultation methods