ENHANCED GEOTECHNICAL EXPLORATION

MYV determines the stratigraphy and nature of subsurface materials at any project site, revealing subsurface conditions that could lead to construction difficulties or potential geotechnical problems. In this regard, MYV has exploration equipment ranging from simple tools to state-of-the art technology. In this field, our main services are as follows:

ENGINEERING GEOLOGY

In either complex geologies or complex problems, the engagement of an Engineering Geologist is key for properly understanding the spatial distribution and properties of geological materials, as well as geological phenomenon such as erosion, local failure planes, and the like. The Geologist plays a key role in the geotechnical exploration, thereby assuring a more precise understanding of the interaction among Geologic Environment – Engineering Issues – Project Development.

BASIC EXPLORATION

SPT (STANDARD PENETRATION TEST)
In Costa Rica, SPT is the most used type of in situ test and its execution usually meets ASTM D1586. The use of this in situ test has advantages as well as disadvantages. Therefore, MYV has mainly used the SPT testing in residential projects and developments. Nevertheless, it was due to SPT disadvantages and shortcomings that MYV decided to introduce enhanced and mega enhanced in situ testing in Costa Rica.

FVT (FIELD VANE TEST)
FVT test stands for Field Vane Test. Its execution meets ASTM D2573. In order to perform FVT tests as professional as possible, MYV decided to purchase the Vane Tester Geonor H-70 that was developed in Norway by Geonor (Commercial Branch of the NGI – Norwegian Geotechnical Institute). The Geonor H-70 allows for safe vane boring down to 10 meters by simple hammering, drilling or pressing. Its unique anti-friction slip coupling system always ascertains the real friction between rods and soil.

TERRIER (ROTARY DRILLING)

Coming soon - Scheduled for Year 2010.

UNDISTURBED SOIL SAMPLING

MYV owns specialized field equipment aimed for extraction of undisturbed soil samples, as required in strength and compressibility testing. The soil sampler is inserted into the ground by means of CPT static push. This sampler is designed by PAGANI (Campeonatore type) and it is rather similar than the MOISTAP sampler from AP VAN DEN BERG. Nominal diameter of the extracted soil sample is 3 inches (76 milimeters). In addition, MYV built its own soil sample ejector system to extract the sample from the tube, by means of compressed air, whose use reduces the disturbance while retrieving the sample. ASTM Standard for undisturbed soil sampling is ASTM D1587-08 (Standard Practice for Thin-Walled Tube Sampling of soils for geotechnical purposes).

NON DESTRUCTIVE TESTING (NDT)

SASW (SPECTRAL ANALYSIS OF SURFACE WAVES)
Standards for the SASW method include ASTM D6758-02 for measuring stiffness and apparent modulus of soil and soil-aggregate in-place by an electro-mechanical method and ACI 228.2R for NDE applications. MYV owns two versions of the SASW equipment: SASW-S (for pavements and structures) and SASW-G (for geologic profiles). The method uses the dispersive characteristics of surface waves to determine the variation of the shear wave velocity (stiffness) of layered systems with depth.

SASW-S (Version for pavements and structures)
SASW-S test method is applied primarily to assess material stiffness and condition, and layer thickness (for profiles no deeper than 3 meters) without the need of drilling or coring. SASW-S is a powerful tool to determine material properties at different depths. SASW-S method can be applied to: identification of damage on concrete elements due to either fire exposure or cracking, estimation of concrete strength (also applies for masonry and rock), determination of surface opening crack depths, determination of resilient modulus of pavement layers (surface layer, base and subgrade materials), condition assessment of concrete liners in tunnels, slabs, and other concrete members, condition assessment of rigid pavements and slabs-on-grade in general.

SASW-G (Version for Geologic Profiles)
SASW-G method (version for geologic profiles) allows determining the variation of the shear wave velocity (Vs) of layered systems with depth, within the first 30 meters bgs (below ground surface). These Vs profiles can be used for: Earthquake Site Response, Liquefaction Analysis, Soil Compaction Control, Mapping subsurface stratigraphy, foundation design of vibratory machines, determination of the natural period (Tn) of soil profiles, determination of VS30 for a given project site (average shear wave velocity over the top 30 meters) and consequently, CSCR-2002 site classification for seismic design of structures (Site Types: S1, S2, S3, S4).

OHMMAPPER
The OhmMapper is a capacitively-coupled resistivity meter that measures the electrical properties of rock and soil without galvanic electrodes used in traditional resistivity surveys. A simple coaxial-cable array is pulled along the ground either by a single person or attached to an all-terrain vehicle. Data collection is continuous so the near surface (top 8 – 10 meters) is finely sampled, providing high quality data even in areas with complex geology. Among important applications of the equipment, the most important are as follows: geologic mapping, detection of geologic faults, detection of fractured zones, detection of aquitards, image of clay layers, measurement of the integrity of levees, detection of voids under roads and building sites, measurement of depth to bedrock, and the like.

PERMEABILITY TESTING IN SITU

Coming soon - Scheduled for Year 2010.

LUGEON / LEFRANC

MCPT (MECHANICAL CONE PENETRATION TEST)
In Cone Penetration Testing (CPT), a cone on the end of a series of rods is pushed into the ground at a constant rate and continuous or intermittent measurements are made of the resistance to penetration of the cone (qc). Simultaneously, measurements are also made of either the combined resistance to penetration of the cone and outer surface of a sleeve or the resistance of a surface sleeve (fs, friction sleeve).

Currently, MYV performs the MCPT (Mechanical CPT) with the Begemann Cone as per ASTM D3441. Nevertheless, in the near future (year 2009-2010), MYV is planning to acquire the CPTU (Cone Penetration Test with pore pressure measurement) commonly referred to as the piezocone.

CPTU (PIEZOCONE)
MYV owns an electric cone (ASTM D5778) type ICONE developed by AP VAN DEN BERG, Dutch company worldwide leader in the industry of equipment for in situ geotechnical exploration. MYV was in interaction with APV in order to produce equipment customized to fit MYV needs. The ICONE uses a DAQ (Data Acquisition System) to digitally capture data coming from the several sensors (cone resistance qc, sleeve friction fs, pore pressure u2, Ix Inclination, Iy Inclination). Data are recorded every 1 – 5 cm of depth, along the whole length of the CPT sounding, at a rate of 2 cm /second. Real time of the data is achieved through the screen of a laptop computer. The piezocone is a unique tool for stratigraphy, identification of soil types, and determination of geotechnical parameters for foundation design (both shallow and deep foundations).

DMT (Marchetti Dilatometer).
A dilatometer test (DMT, ASTM D6635 and Eurocode 7 – Part2) consists of pushing a flat blade located at the end of a series of rods. Once at the testing depth, a circular steel membrane located on one side of the blade is expanded horizontally into the soil. Typically, Nitrogen gas is used to inflate the circular membrane. The pressure is recorded at specific moments during the test:

• the A-pressure, required to just begin to move the membrane against the soil ("lift-off")
• the B-pressure, required to move the center of the membrane 1.1 mm against the soil.
• A third reading C ("closing pressure") can be taken by slowly deflating the membrane soon after B is reached.

Once the membrane deflated completely, the blade is then advanced to the next test depth.
The main engineering application of the DMT is for settlement calculation of shallow foundations on either Sand or Clay deposits, as well as the estimation of strength parameters for both cohesive and granular soils. Other applications are as follows: compaction control, detection of slip surface in landslides, assessment of liquefaction potential, calculation of P-Y curves for laterally loaded piles and calculation of axial capacity of driven piles as well as drilled shafts, and analysis of geotechnical problems using the soil parameters for which the instrument provides estimates.
During the past years, MYV has become highly specialized in the use of the DMT because of two (2) main factors: A) A number of big and small projects for which the geotechnical exploration was carried out by means of our DMT and B) A continuous and kind assistance on the side of Prof. Silvano Marchetti (inventor of the DMT) with whom MYV has a close working relationship with since our visit to Studio Marchetti located at Rome, Italy for a 3-days training course (year 2006).

PRESSUREMETER PMT TEXAM

Coming soon - Scheduled for Year 2010.

ASTM D4719-00

MEGA ENHANCED IN SITU TESTING

SDMT (Seismic Dilatometer).
SDMT (Seismic Dilatometer) is the combination of the standard Flat Dilatometer (DMT) with a seismic module. Such module is a probe outfitted with two receivers, spaced 0.5 m, for measuring the shear wave velocity Vs. From Vs one can determine the small strain shear modulus Go. SDMT provides profiles of Vs in a quick and precise way (repeatability of Vs 1-2 %). SDMT provides, besides Vs, all the information obtained by the traditional DMT.
According to Prof. Dr. Paul Mayne from GeorgiaTech, SDMT is one of the most advanced in situ tests there is worldwide in characterizing mechanical properties of soils (static and dynamic properties).
We MYV have performed several SDMT soundings with a Campanella pendulum hammer as a wave-generating system. Nevertheless, last year MYV imported an AUTOSEIS from Vancouver, Canada (ConeTec), which is an automatic seismic source designed by the GeorgiaTech. The Autoseis source can increase both consistency and productivity of both SDMT soundings (Seismic Dilatomer) and SCPTu soundings (Seismic Piezocone).

GEOSTATISTICAL MAPS / 3D MODELS OF THE GROUND SUBSURFACE

MYV has been involved in a continuous cycle of research process - practical applications on the use of geostatistic techniques (spatial distribution of geomechanical properties) and RBD techniques (Reliability Based Design). In this manner, MYV has gained insight on the use of these techniques as tools to create maps of the spatial distribution of ground properties such like: strata thickness, undrained strength, constrained modulus M, and the like. This is a highly practical approach, specially used to generate synthetic data at those locations of the project where no exploration soundings are available