Geotechnical Terminology

Auger: This is a drilling tool that is shaped like a cork screw; it is used to drill holes in the ground without the use of water or air; this method of boring a hole is free of vibrations and does not need the impact typically associated with drilling tasks.

Bentonite: It is a clay like material that is extracted from the mines in the mid-west. The substance is ground into a powder and is subsequently used in test drilling to make sure that the drill hole does not cave in. It is also used in cosmetic and food preparations such as candy bars.

Compaction Grouting: This is a standard grouting technique used to cover and stabilize subsidence sinkholes; pressure grouting and compaction grouting differ in terms of the material used for grouting; the material used in compaction grouting is thick enough to fill the voids; this mortar like substance displaces the soft upper layers of the soil.

Concrete Pumping: concrete pumping is the technique used to pump concrete in areas where a quick and steady supply is needed. Because concrete is a fluid it can be fed to various areas of the site through concrete pumps, concrete pumping is generally used to feed a point on the site where slab is being poured

Fly Ash: Fly ash is the gray, fine powder that is produced when an electrical plant is used to burn coal; this is one of the ingredients of grout mixture along with sand; together the mixture is deal for filling small voids. Fly ash is particularly essential when pumping the grouting mixture underground.

Foundation: The underground structural system of a building that supports the construction by transferring the weight of the structure to the ground

Geotechnical: Science that deals with soil that lies below the surface of the ground

Geotechnical Report: This is a report that includes the results of tests and expert opinion offered by a geotechnical engineer or a specialty engineering firm. The report will include information derived through soil boring experiments; ground penetrating radar analysis and other tests specifically designed and undertaken to study the soil condition at the site.

Granular: Refers to the surface appearance of a fill being ‘meal like’ or coarse in nature; granular fills are a combination of crushed gravel or sand gravel and pit run gravel that is placed in excavations

Grout: This material is similar to the mortar that is typically used in brickwork; grout is cement based and is designed specially to include fine sand, Portland cement, water and fly ash. Depending on the project for which the mixture will be used; small stones may also be included. The material is not made on site rather it is delivered to the site of a residential stabilization project by concrete suppliers. Grout has a compressive strength of 1000 psi in 28 days and it reaches its initial in 2 hours.

Grout Casing Injection Pipe: This is a steel pipe of considerable strength with a diameter of at least three inches. It is manufactured with the use of flush joints with internal threaded grout casing that is specially designed for the purpose. Standard coupled and threaded pipes would prove futile and should not be used. The casing goes on top of the lime stone initially; however it is withdrawn as the grout injection process is under way.

Grout Design Mix: In simple words; this is recipe for the grout mixture used in most residential compaction grouting jobs; the mixture typically contains fine sand, water, cement, fly ash; and depending on the project, also small stones. The composition of grout design mixes may differ among contractors

Grout Injection Point: This is the hole that is drilled in the ground for injecting the grout mixture into the soil; if the project entail sinkhole stabilization; the hole is drilled on top of firm limestone. The depth of the grout injection point will depend on the local conditions. It is drilled with the help of continuous flight augers or by using a steel pipe while a drilling fluid is being used. Regardless of the technique used; it is imperative to install flush joint casing in the entire depth of the hole before the grout material is injected.

Grout Monitor: The term refers to an employee of an engineering company that has been entrusted the task of monitoring the stabilization project. The technician is responsible for recording the drill depths; grout takes and other specific details about the project

Gunite: Gunite is a term commonly used for mortar or concrete mixtures used for pressure applications.

Heave: Refers to the movement of the soil upwards; several factors can cause such movement; however, the typical causes of heave in residential soil stabilization are:

• Clay: Highly active, plastic clays have the ability to absorb a lot of moisture; consequently the turgid molecules of clay can lift or heave the concrete or structure situation above it
• Organic soil: Organic soil is typically rich in decaying plant matter such as wood, roots and peat. Over the period of a few years; the organic matter continues to decay thus reducing in volume; a structure constructed on top of such soil will experience subsidence as the soil decreases in volume
• Grout: When grout is being injected into the soil at high pressure; a hydraulic reaction may come into play that makes the surface soil rise. However, this procedure is often used to correct anomalies in structures that have settled. Heave should be detected with appropriate instruments when grouting around an existing structure.

Hydrostatic Pressure: It can be described as the pressure exerted by a fluid when it is at equilibrium ( at rest).

Karst: Karst geology refers to areas where limestone lies below the surface soils; some of this limestone is practically dissolved by groundwater; this in turn creates voids that serve as a channel for water to travel along with the erodible soil

Limestone: Refers to a type of sedimentary rock that is primarily comprises of calcium carbonate.

Lump Sum: The term refers to the total amount of agreed upon price charged for an item that has been bid on

Professional Engineer: The term refers to a professionally qualifies licensed engineer which can undertake the task of designing certain activities for projects.

Proposal: Is a document provided y the contracting company to the service buyer that outlines the tasks that will be carried out for the purpose of stabilization. The proposals, apart from other factors, should be based on and must adhere to the design recommendations made in the project specification or geotechnical report. The proposal will also contain information on the estimated depth of lineal feet of drilling and the grout material that the contractor intends to use for the stabilization project. The final quantity of the grout material should be the same as stated in the original estimate and to ensure this, you will need to work with a highly experienced contractor.

Mold Remediation: refers to the procedures used to remove mold build up from an internal space such as an office, school or home. If there is limited mold infestation, the home owner can deal with it on his own but incase of wide spread mold, professional help should be enlisted.

Mudjacking: This is the procedure used to pump high pressured grout underneath a concrete slab to fill voids to even the surface and correct elevation problems. Mud jacking is usually considered when a concrete slab tilts over the years and replacement of the slab has to be considered by the home owners; in such a case, mudjacking is a significantly cheaper solution than slab replacement. The procedure is also known as slab jacking.

Refactory: The term fryers to the attributes of materials that are stable at high temperatures; these are generally used in the construction of furnaces.

Rock Fall: This refers t the quantities of free fall rock blocks that are detached from a cliff face by sliding.

Rock Strata: refers to a layer of rock that has consistent characteristics that distinguish it from the other rocks. Geologist categorize rock strata by the composition of the material in the bed

Settlement: This refers to the vertical movement of the ground downwards or to the downward movement of a structure or element placed on top of the soil surface

Shotcrete: This is a concrete or mortar mixture that is applied through the use of pressure hoses.

Sinkhole: This is a condition that develops due to the dissolving of limestone; the process takes place at the subsurface level and it causes a depression that is a result of the soil and other material sinking into the void below the surface. It is also termed as subsidence sinkholes or covered collapse

Slabjacking: Also known as mud jacking, slab jacking is the procedure used to correct concrete level anomalies that creep in after years of use. If the concrete slab is sinking; possibilities are that the slab was initially installed on poorly compacted soil. A slabjacker will be able to drill holes in the slab to inject a mixture of fly ash, cement, fine sand and water so that the concrete can be lifted.

Slope Stabilization: Is the process of implementing the recommendations in a slope stability report; these are steps taken to retain the stability of slopes when designing excavation such as foundations, open pits and quarries; stabilization procedures have to be implemented where movement may pose a hazard. Slope stabilization can be achieved through techniques such a grouting; dewatering, rock bolting, shotcreting, meshing or a combination of these techniques.

SPT Abbreviation for Standard Penetration Test: This is a standard industrial procedure used to measure the density of the subsurface soil. The test is conducted to determine the number of blows that would be required to advance a steel test spoon one foot by the force generated by dropping a hammer (140 pounds) by thirty inches. The number of blows required to achieve the desired result is referred to as N value.

Subsidence Settlement: The vertical movement of the ground downwards is known as subsidence settlement; several factors may cause this phenomenon to occur such as:

• Organics: When the oil is composed of decaying plant matter it is prone to subsidence over a period of time as the decay decreases the volume of the soil which in turn cause serious settlement problems to any structure constructed on such soil
• Clay: Plastic clays have the ability to absorb and retain a lot of moisture which in turn increases the volume of the clay soil causing an upward movement of any structure erected on the soil
• Poorly Compacted Soil: It is essential to compact the soil appropriately before laying the foundation for a structure; if the soil is not compacted, there is a strong likelihood of it compressing beneath the weight of concrete slabs and causing subsidence.
• Sinkholes: The term refers to the presence of limestone at the sub surface level; this limestone dissolves in the ground water over time creating voids, fractures ad cavities. These in turn act like channels for the percolation of water; once the pathway is large enough, soil also sinks in resulting in a gradual downward movement of any structure placed on such soil
• Poor Quality Construction Technique: Any compromise in the quality of design of the structure will make it prone to cracks and other structural faults such as settlement. Often, additional wings of a home may be built without laying the proper foundation this may also cause subsidence.

Steel Piering: This is the procedure used to transfer the weight of a structure from problematic soil surface to an appropriate load bearing strata like a rock bed. Residential steel piering is conducting by installing steel pipe sections adjacent to the foundation. These pipes are drilled down or hydraulically jacked into the bearing zone. Subsequently, a foundation bracket is mounted on top to transfer the weight to the mini pile.

Sump Pump: This is a device used to pump water out of a water collecting sump pits that are built in the basement of homes

Target Quantity: This is a pre determined and affixed quantity of grout material that is injected into a particular zone

Unit Price: The price per cubic yard of grout material is  known as the unit price

Water Table: The sub surface level at which the soils is saturated with water.

Waterproofing: This is a process used to prevent water leakage in a building; water resistant substances are used to coat the walls and ceiling of the structure that will prevent water seepage.