GeotechUnit - opengeospatial/Geotech GitHub Wiki
What is a GeotechnicalUnit?
A surface or a volume in which the mechanical behaviour and other design-relevant characteristics are characterized using the same geotechnical parameters values. Several alternative classifications can be required in a project for different design tasks.
Realizations
| Data model | Concept name | Definition |
|---|---|---|
| IFC | GeotechUnit | A surface or a volume in which the mechanical behaviour and other design-relevant characteristics are characterized using the same geotechnical parameters values. Several alternative classifications (=GeotechModels) can be required in a project for different design tasks. |
| OGC GeoSciML | GeotechUnit (as a GeologicUnit with Type = GeotechnicalUnit) | Same as IFC 4.4+ |
| DIGGS | GeoUnitObservation | Descriptions of a soil or rock where the unit is primarily defined by the value(s) or a value range of one or more physical or engineering properties. The criteria for distinguishing such units may vary depending on the engineering application. |
| AGSi | agsiModelElement | In AGSi a model is collection of elements (agsiModelElement object) and this may include geotechnical units, identified as such using the elementType attribute. |
Properties
The GeotechUnit concept distinguish SoilLikeMaterial and IntactRockMaterial. Each having its own characteristics. The tables below list relevant properties for those types of GeotechUnit. Some being interpreted, calculated or derived from measurements.
Inherited properties from the GeologicUnit concept
See GeologicUnit
Relevant properties for soil like material
| Property name | Definition |
|---|---|
| WaterContent | Ratio of the mass of water to the mass of solids |
| VoidRatio | Ratio of the volume of void to the volume of solid |
| WetBulkDensity | Ratio of the total mass to the unit total volume (material at its natural moisture content) |
| DryBulkDensity | Ratio of the mass of solid to the unit total volume (dry material) |
| Emodulus | The elastic modulus (E-modulus) is a measure of the ground stiffness, describing the extent to which a material resists deformation in response to an applied force. It is defined as the ratio of the stress along an axis to the strain along that axis in the range of elastic behaviour. This property can be measured directly with different types of laboratory and in-situ test methods and is used in constitutive models for soil and rock.Many alternative and corresponding parameters describe the ground stiffness, including elastic and plastic behaviour and depending on strain (non-linear behavior), loading/unloading conditions, dynamic/static conditions, drained/undrained conditions. Such specific parameters can be defined in IFC models with custom property sets depending on the exchange scenario (e.g. for specific test results or geomechanical properties of interpreted models and materials). |
| MenardLimitPressure | Limit pressure, resulting from interpretation of Menard's pressuremeter test |
| CPTconeResistance | Cone penetration resistance measured during the CPT test |
| SPTBlowCount | Number of blows N required to drive the sampler for a test drive of 300 mm following the seating drive. |
| PlasticityIndex | The plasticity index Ip is the numerical difference between the liquid limit and plastic limit of a fine soil. IP = wL − wP |
| ConsistencyIndex | The consistency index (Ic) indicates the consistency (firmness) of a soil. It is the numerical difference between the liquid limit and the natural water content expressed as a percentage ratio of the plasticity index. Ic = (LL-W)/Ip |
| PeakCohesion | Cohesion is a shear strength parameter of soils. Its definition is derived from the Mohr-Coulomb failure criterion and it is used to describe the shear resistance of soils that is independent from the normal effective stress. The peak value correspond to the maximum shear measured during the test. |
| ResidualCohesion | Cohesion is a shear strength parameter of soils. Its definition is derived from the Mohr-Coulomb failure criterion and it is used to describe the shear resistance of soils that is independent from the normal effective stress. The residual value correspond to the shear strength measured at large strain values during the test. |
| PeakFrictionAngle | Soil effective stress friction angle is a shear strength parameter of soils. Its definition is derived from the Mohr-Coulomb failure criterion and it is used to describe the friction shear resistance of soils with the normal effective stress. The peak value correspond to the maximum shear strength measured during the test. |
| ResidualFrictionAngle | Soil effective stress friction angle is a shear strength parameter of soils. Its definition is derived from the Mohr-Coulomb failure criterion and it is used to describe the friction shear resistance of soils with the normal effective stress. The residual value correspond to the shear strength measured at large strain values during the test. |
| UndrainedShearStrength | Shear strength of a soil under undrained condition or constant volume conditions. It is relevant for conditions where the rate of loading is very much greater than the rate at which pore water pressure - generated due to the action of shearing of the soil - dissipates. Its calculation depends on the laboratory test performed. |
| PoissonRatio | Ratio between radial/horizontal strain and axial strain of a (geo)material when compressed. |
| Emodulus | The elastic modulus (E-modulus) is a measure of the ground stiffness, describing the extent to which a material resists deformation in response to an applied force. It is defined as the ratio of the stress along an axis to the strain along that axis in the range of elastic behaviour. This property can be measured directly with different types of laboratory and in-situ test methods and is used in constitutive models for soil and rock.Many alternative and corresponding parameters describe the ground stiffness, including elastic and plastic behaviour and depending on strain (non-linear behavior), loading/unloading conditions, dynamic/static conditions, drained/undrained conditions. Such specific parameters can be defined in IFC models with custom property sets depending on the exchange scenario (e.g. for specific test results or geomechanical properties of interpreted models and materials). |
| CompressionIndex | Compression index is determined with the oedometer tests, and used to compute settlements. |
| SwellingIndex | Swelling index is determined with the oedometer test, and used to compute swelling. |
| OCR | Ration between preconsolidation pressure and overburden pressure. |
| K0 | The coefficient of lateral earth pressure, K, is defined as the ratio of the horizontal effective stress, σ’h, to the vertical effective stress, σ’v. For a level ground deposit with zero lateral strain in the soil, the "at-rest" coefficient of lateral earth pressure, K0 is obtained. |
| RelativeDensity | Relative density or density index is the ratio of the difference between the void ratios of a cohesionless soil in its loosest state and existing natural state to the difference between its void ratio in the loosest and densest states. (emax - e) /(emax-emin). |
Relevant properties for intact rock
| Property name | Definition |
|---|---|
| UCS | The unconfined compressive strength (UCS) is the maximum axial compressive stress that a right-cylindrical sample of material can withstand under unconfined conditions |
| Emodulus | The elastic modulus (E-modulus) is a measure of the ground stiffness, describing the extent to which a material resists deformation in response to an applied force. It is defined as the ratio of the stress along an axis to the strain along that axis in the range of elastic behaviour. This property can be measured directly with different types of laboratory and in-situ test methods and is used in constitutive models for soil and rock.Many alternative and corresponding parameters describe the ground stiffness, including elastic and plastic behaviour and depending on strain (non-linear behavior), loading/unloading conditions, dynamic/static conditions, drained/undrained conditions. Such specific parameters can be defined in IFC models with custom property sets depending on the exchange scenario (e.g. for specific test results or geomechanical properties of interpreted models and materials). |
| PoissonRatio | Ratio between radial/horizontal strain and axial strain of a (geo)material when compressed. |
| TensileStrength | Cylindrical rock specimen, extended along two diametrically opposed generatrices. This test piece is placed between two plates so that the two generators are in contact with the two plates. An increasing force is applied until the test piece breaks |
| MineralComposition | Description of the mineral composition according to ISO standard 14689:2017 |
| VoidRatio | Ratio of the volume of void to the volume of solid |
| Weathering | Description of the physical and chemical changes produced by atmospheric agents in rocks or other deposits at or near the earth's surface. These changes result in disintegration and de composition of the material. |
Discontinuities in rock
| Property name | Definition |
|---|---|
| RQD | Quotient of the cumulative length of cores with a length greater than 10 cm, by the total length of the core pass with a length greater than or equal to 1m |
| DiscontinuityType | pattern of bedding, folds, faults and discontinuities in rock masses, which subdivide the mass into individual domains or rock blocks (ISO14689) |
| DiscontinuityStrikeDirection | The geographic direction of a line created by the intersection of a plane and the horizontal plane. If non specific convention is used, this angular value is in the range 0 to 18 degrees. In this case, there is an ambiguity on the dip orientation. For example, a plane with an orientation of 90 degrees from the nord could either have a dip direction to the North or to the South. Thus, to avoid this ambiguity, a strike value is generally completed with an indication of the dip orientation (Quadrant). |
| DiscontinuityDipAngle | The dip is the steepest angle of descent of a géological plane to a horizontal plane. It's value its in the range 0 to 90 degrees. |
| DiscontinuitySpacing | The term “spacing” refers to the mean or modal spacing of a set of discontinuities and is the perpendicular distance between adjacent discontinuities. The number of discontinuity sets, the differences in spacing and the angles between the sets shall be reported as these determine the block shape. The discontinuity spacing should be measured in millimetres and can be classified using the terms in Table 8. (ISO14689) |
| DiscontinuityPersistence | The linear extent of discontinuities from their inception to their termination in solid rock mass or against other discontinuities or outside the exposure shall be reported. The size of the exposure shall also be recorded. If possible and appropriate, measurements should be made in two or preferably three orthogonal directions. (ISO14689) |
| DiscontinuityAperture | The perpendicular distance between the two surfaces of a discontinuity is referred to as the aperture. (ISO14689) |
| DiscontinuityInfilling | The infilling material between discontinuity surfaces shall be identified and described (e.g. soil,minerals such as calcite, quartz, epidote, chlorite, anhydrite, clay gouge, rock gouge or breccia). (ISO14689) |
| DiscontinuityRoughness | The surface condition and the shape of discontinuities shall be described on the basis of three scales of observation, respectively, and using the terms given in Table 9 and illustrated in Figure 2: a) small scale (several millimetres) — smooth or rough; b) medium scale (several centimetres) — planar, stepped or undulating; c) large scale (several metres) — straight, curved or wavy. (ISO14689) |
| DiscontinuityWaterPresence | Descriptive of estimated waterinflow in excavation, to be used to define Jw(Barton), or RMR groudnwater inflow rating. |
| Cohesion | Cohesive shear strength of a rock or soil that is independent of interparticle friction. |
| FrictionAngle | Derived from the Mohr-Coulomb failure criterion and used to describe the friction shear resistance of ground materials, together with the normal effective stress. |
Properties for rock mass
| HoekBrownMi | material constant of intact rock |
|---|---|
| RQD | Quotient of the cumulative length of cores with a length greater than 10 cm, by the total length of the core pass with a length greater than or equal to 1m |
| RMR | The rock mass rating (RMR) is a geomechanical classification system for rocks, developed by Z. T. Bieniawski |
| QValue | The rock mass quality (Q) is a very sensitive index and its value varies from 0.001 to 1000. Use of the Q-system is specifically recommended for tunnels and caverns with an arched roof. |
| GSI | The Geological Strength Index (GSI): A characterization tool for assessing engineering properties for rock masses. |
| Emodulus | The elastic modulus (E-modulus) is a measure of the ground stiffness, describing the extent to which a material resists deformation in response to an applied force. It is defined as the ratio of the stress along an axis to the strain along that axis in the range of elastic behaviour. This property can be measured directly with different types of laboratory and in-situ test methods and is used in constitutive models for soil and rock.Many alternative and corresponding parameters describe the ground stiffness, including elastic and plastic behaviour and depending on strain (non-linear behavior), loading/unloading conditions, dynamic/static conditions, drained/undrained conditions. Such specific parameters can be defined in IFC models with custom property sets depending on the exchange scenario (e.g. for specific test results or geomechanical properties of interpreted models and materials). |
| Cohesion | Cohesive shear strength of a rock or soil that is independent of interparticle friction. |
| FrictionAngle | Derived from the Mohr-Coulomb failure criterion and used to describe the friction shear resistance of ground materials, together with the normal effective stress. |
| K0 | Lateral Earth Pressure Coefficient |
Extra properties
| Property name | Definition |
|---|---|
| PwaveVelocity | Value of S wave (Shear wave (S)) measured through the unit. |
| SwaveVelocity | Value of P wave (pressure or primary elastic body wave (P)) measured through the unit. |
| Resistivity | Electrical resistivity of a rock or soil (Ohm-m). |
| GroundwaterTemperature | Temperature measured or assumed in the groundwater |
| WetBulkDensity | Ratio of the total mass to the unit total volume (material at its natural moisture content) |
| DryBulkDensity | Ratio of the mass of solid to the unit total volume (dry material) |