Test Pits and Bulk Sampling
Teragrail GG offers manual test pit excavations in order to sample and study the composition and structure of the subsurface material. This is usually done simultaneously with site investigation and during pre-feasibility studies. Depending on the soil, test pits can be dug up to 10.0-m (with benching/shoring). Test pit excavations provide vital information on the material contacts, particle sizes and classification, extend of buried debris and other environmental factors that can affect the project site.
A borehole is a narrow vertical shaft bored in the ground. This is conducted during geotechnical investigation or environmental site assessment prior to construction for site analysis. This is to establish whether or not a site is going to be appropriate for construction and if ground improvement measures needed to mitigate site effects can be implemented to stabilize soil or rock.
This is because unsafe soil or rock conditions can trigger structural collapse or cause hazardous scenario during an earthquake or flood. Geotechnical drilling involves the preparation for foundations, caissons and various supports and can also be used for the search for ground water, identification of key minerals and subsurface composition and classify an area’s susceptibility to liquefaction, settlement and lateral spreading.
The Engineering Geological and Geohazard Report or more commonly referred to as the EGGAR, is an additional requirement for the issuance on an Environmental Compliance Certificate or ECC under the Presidential Decree No. 1586, Presidential Proclamation No. 2146 and its implementing rules and regulations where all proponents of subdivision development projects, housing projects and other land development and infrastructure projects, private or public, shall undertake an Engineering Geological and Geohazard Assessment.
The primary objective of geological field mapping is to identify the occurrence and extent of geological and structural features across an area – distribution of rock units, identification of soil type and composition and age relationship of major lithological units. Field mapping is the process of selecting an area of interest and identifying al the geological aspects with the purpose of preparing a detailed geological report. This is mainly broken down into three phases:
Literature Review and Planning
Fieldwork & Data Collection
The geologist may opt to conduct other tests for identifying the type of material and the strength of the material by employing petrographic analysis and other forms of laboratory testing. In addition, the area is also checked for its susceptibility to landslides, flooding, or any hazards that can potential do harm or damage.
Geological Field Mapping is usually done on a large scale and can last for days, weeks or even months depending on the site’s area.
Site Speciﬁc Investigation
Once a speciﬁc area has been identiﬁed, it’s best to conduct site investigation. This is performed by either a geotechnical engineer or an engineering geologist to obtain information on the physical properties of soil earthworks and foundations for a proposed structure and assess how the underlying soil and site conditions can affect it.
Dynamic Cone Penetrometer (DCP) Testing
An easy way to estimate the bearing capacity of a soil.
Dynamic Cone Penetration (DCP) Testing is used to measure the strength of in-situ soil and the thickness and location of subsurface soil layers. In DCP testing, the pushing force is applied by manually dropping a hammer from a ﬁxed height onto the rod. The number of blows per advance (mm/cm) is then measured and the soil’s bearing capacity may be estimated.
Unlike other drilling and investigation systems, basic DCP equipment is very portable but is limited to depths of up to 3.0-m which makes this type of testing ideal for roads, pavements, poles, light-weight cell towers and even 1 to 2 storey structures.
Refraction Microtremor (REMI), Seismic Reﬂection, Vibration Monitoring, MASW
Teragrail’s seismic surveys are used for investigation subsurface ground conditions by utilizing surface-sourced seismic waves. Data acquired on site is then processed and interpreted to produce models of seismic velocity and layer thickness of the subsurface ground structure. This method is non destructive and may be used in pre-feasibility and feasibility studies and in some cases, may be used as an alternative to borehole drilling. Its main applications are:
Measures bedrock depth & overburden thickness;
Determines seismic rippability parameters;
Investigates pipeline routs;
Locates geological structures; and,
Evaluates sand & gravel deposits.
Detailed liquefaction analysis using multiple methods
Liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or rapid loading. This occurs in saturated soils where the space between individual particles is completely ﬁlled with water.
Teragrail can provide you a complete analysis of liquefaction using qualitative (geomorphology) and quantitative methods by different authors.