Poroelasticity Calculations - Revision history

Nairnj at 17:26, 29 March 2026

2026-03-29T17:26:00Z

← Older revision		Revision as of 17:26, 29 March 2026
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	[[NairnMPM]] can do poroelasticity calculations coupled with stresses and strains through tracking of pore pressure in fluid-saturated media.		[[NairnMPM]] can do poroelasticity calculations<ref name="transport/> coupled with stresses and strains through tracking of pore pressure in fluid-saturated media.
	__TOC__		__TOC__
	== Introduction ==		== Introduction ==

	Poroelasticity is modeled by extension of methods first described by Biot.<ref name='poro'~~>M. A. Biot. General theory of three dimensional consolidation. J. Appl. Phys., 12:155–164, 1941.<~~/~~ref~~> In brief, each particle tracks a pore pressure that models pressure within a liquid for a material saturated with that liquid. As the material volume changes, the pore pressure increases or decreases. The pore pressure can transport between particles based on Darcy tensor for permittivity of the material for the given liquid. Some [[Common Material Properties#Poroelasticity Properties\|poroelasticity material properties]] control coupling between stresses and strains and the pore pressure.		Poroelasticity is modeled by extension of methods first described by Biot.<ref name='poro'/> In brief, each particle tracks a pore pressure that models pressure within a liquid for a material saturated with that liquid. As the material volume changes, the pore pressure increases or decreases. The pore pressure can transport between particles based on Darcy tensor for permittivity of the material for the given liquid. Some [[Common Material Properties#Poroelasticity Properties\|poroelasticity material properties]] control coupling between stresses and strains and the pore pressure.

	The extensions from Biot<ref name="poro"/> are to model poroelasticity in anisotropic materials and to allow the pore pressure to [[#Negative Pore Pressure\|drop below zero]].		The extensions from Biot<ref name="poro"/> are to model poroelasticity in anisotropic materials and to allow the pore pressure to [[#Negative Pore Pressure\|drop below zero]].
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	<ref name="transport">J. A. Nairn, "Coupling Transport Equations to Mechanics in the Material Point Method Using an Approximate Full Capacity Matrix Inverse," ''Computer Methods in Applied Mechanics and Engineering'', '''420''', 116757 (2024). ([https://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/TransportPaper.pdf See PDF])</ref>		<ref name="transport">J. A. Nairn, "Coupling Transport Equations to Mechanics in the Material Point Method Using an Approximate Full Capacity Matrix Inverse," ''Computer Methods in Applied Mechanics and Engineering'', '''420''', 116757 (2024). ([https://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/TransportPaper.pdf See PDF])</ref>

			<ref name='poro'>M. A. Biot. General theory of three dimensional consolidation. J. Appl. Phys., 12:155–164, 1941.</ref>

	</references>		</references>

Nairnj: /* References */

2026-03-29T17:25:12Z

References

← Older revision		Revision as of 17:25, 29 March 2026
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	== References ==		== References ==

	<references/>		<references>

			<ref name="transport">J. A. Nairn, "Coupling Transport Equations to Mechanics in the Material Point Method Using an Approximate Full Capacity Matrix Inverse," ''Computer Methods in Applied Mechanics and Engineering'', '''420''', 116757 (2024). ([https://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/TransportPaper.pdf See PDF])</ref>

			</references>

Nairnj: /* Activating Poroelasticity */

2023-08-23T23:27:22Z

Activating Poroelasticity

← Older revision		Revision as of 23:27, 23 August 2023
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	Note that poroelasticity models fluid transport through materials by transport methods nearly identical to those used to model [[Diffusion Calculations\|diffusion]]. Because they share same methods, a simulation can activate poroelasticity (with above commands) or diffusion (with comparable [[Diffusion Calculations\|Diffusion commands]]), but cannot activate them both. Any simulation, however, can combine poroelasticity or diffusion with [[Thermal Calculations\|thermal calculations and conduction]]. Note that when choosing [[MPM Input Files#Archiving Results\|archiving options]], the terms "concentration" and "porepressure" are synonyms or either can be used and the archiving will store concentration terms for [[Diffusion Calculations\|diffusion calculations]] or pore pressure terms for poroelasticity calculations.		Note that poroelasticity models fluid transport through materials by transport methods nearly identical to those used to model [[Diffusion Calculations\|diffusion]]. Because they share same methods, a simulation can activate poroelasticity (with above commands) or diffusion (with comparable [[Diffusion Calculations\|Diffusion commands]]), but cannot activate them both. Any simulation, however, can combine poroelasticity or diffusion with [[Thermal Calculations\|thermal calculations and conduction]]. Note that when choosing [[MPM Input Files#Archiving Results\|archiving options]], the terms "concentration" and "porepressure" are synonyms or either can be used and the archiving will store concentration terms for [[Diffusion Calculations\|diffusion calculations]] or pore pressure terms for poroelasticity calculations.

			Note that poroelasticity calculations are often improved by using [[PeriodicXPIC Custom Task#Using FMPM(k) For Transport Properties\|FMPM(k) methods]]. They may even require FMPM(k) for stability.

	== Poroelasticity Material Properties ==		== Poroelasticity Material Properties ==

Nairnj at 17:04, 4 January 2021

2021-01-04T17:04:06Z

← Older revision		Revision as of 17:04, 4 January 2021
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	* You can set [[Setting Velocity and Transport Values#Concentration or Poroelasticity Conditions\|pore pressure on the grid]].		* You can set [[Setting Velocity and Transport Values#Concentration or Poroelasticity Conditions\|pore pressure on the grid]].
	* You can set a [[Setting Forces and Fluxes#Concentration or Pore Pressure Flux Conditions\|pore pressure flux on particle surfaces]].		* You can set a [[Setting Forces and Fluxes#Concentration or Pore Pressure Flux Conditions\|pore pressure flux on particle surfaces]].
	* Apply initial pore pressure field to particles using a [[~~ThermalRamp~~ Custom Task]].		* Apply initial pore pressure field to particles using a [[PropertyRamp Custom Task]].
	* [[Rigid Material\|Rigid particles]] can provide moving pore pressure boundary conditions.		* [[Rigid Material\|Rigid particles]] can provide moving pore pressure boundary conditions.

Nairnj: /* Supported Materials */

2021-01-01T19:33:23Z

Supported Materials

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	* [[Isotropic Material]]		* [[Isotropic Material]]
	* [[Isotropic Softening Material]]		* [[Isotropic Softening Material]]
	* [[Transversely Isotropic Material\|Transversely Isotropic Material 1 (or 2)]] - always uses [[Common Material Properties#Basic Properties\|large rotation mode]]		* [[Transversely Isotropic Material\|Transversely Isotropic Material 1 (or 2)]] - always uses [[Common Material Properties#Basic Properties\|large rotation mode]] whether set or not
	* [[Orthotropic Material]] - always uses [[Common Material Properties#Basic Properties\|large rotation mode]]		* [[Orthotropic Material]] - always uses [[Common Material Properties#Basic Properties\|large rotation mode]] whether set or not

	When doing poroelasticity calculations, each material must specify <math>\alpha</math>, <math>K_u</math>, and <math>k</math>. Anisotropic materials must specify values of <math>\alpha</math> and <math>k</math> along the each symmetry plane direction. The property names for entering these material properties are in the [[Common Material Properties#Poroelasticity Properties\|poroelasticity properties tables]].		When doing poroelasticity calculations, each material must specify <math>\alpha</math>, <math>K_u</math>, and <math>k</math>. Anisotropic materials must specify values of <math>\alpha</math> and <math>k</math> along the each symmetry plane direction. The property names for entering these material properties are in the [[Common Material Properties#Poroelasticity Properties\|poroelasticity properties tables]].

Nairnj at 19:11, 1 January 2021

2021-01-01T19:11:39Z

← Older revision		Revision as of 19:11, 1 January 2021
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	[[NairnMPM]] can do poroelasticity calculations coupled with stresses and strains through tracking of pore pressure in fluid-saturated media~~. This feature is only available in [[OSParticulas]]~~.		[[NairnMPM]] can do poroelasticity calculations coupled with stresses and strains through tracking of pore pressure in fluid-saturated media.
	__TOC__		__TOC__
	== Introduction ==		== Introduction ==

Nairnj: /* Activating Poroelasticity */

2021-01-01T19:11:19Z

Activating Poroelasticity

← Older revision		Revision as of 19:11, 1 January 2021
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	* <tt>(eta)</tt> is fluid viscosity for fluid in the pores (and same for all materials). Default is 1 cP in Legacy units or 1 [[ConsistentUnits Command#Legacy and Consistent Units\|viscosity unit]] in consistent units (note that Legacy units default to water viscosity, but consistent units default to 1 [[ConsistentUnits Command#Legacy and Consistent Units\|viscosity unit]] which may not be water viscosity - it is therefore best to always enter this viscosity and not rely on default setting being for water).		* <tt>(eta)</tt> is fluid viscosity for fluid in the pores (and same for all materials). Default is 1 cP in Legacy units or 1 [[ConsistentUnits Command#Legacy and Consistent Units\|viscosity unit]] in consistent units (note that Legacy units default to water viscosity, but consistent units default to 1 [[ConsistentUnits Command#Legacy and Consistent Units\|viscosity unit]] which may not be water viscosity - it is therefore best to always enter this viscosity and not rely on default setting being for water).

	By default, poroelasticity uses update methods analogous to FLIP methods used in mechanics. This update, however, sometimes results in pore pressure oscillations on particles within one cell. Poroelasticity simulations with oscillations can be improved by using [[PeriodicXPIC Custom Task#Using FMPM(k) For Transport Properties\|periodic FMPM(k)]] for poroelasticity updates. In fact, because poroelasticity is inherently stiffer then conduction or diffusion, it may require FMPM(k) for stable simulations.		By default, poroelasticity uses update methods analogous to FLIP methods used in mechanics. This update, however, sometimes results in pore pressure oscillations on particles within one cell. Poroelasticity simulations with oscillations can be improved by using [[PeriodicXPIC Custom Task#Using FMPM(k) For Transport Properties\|periodic FMPM(k)]] for poroelasticity updates. In fact, because poroelasticity is inherently stiffer then [[Thermal Calculations\|conduction]] or [[Diffusion Calculations\|diffusion]], it may require FMPM(k) for stable simulations.

	Note that poroelasticity models fluid transport through materials by transport methods nearly identical to those used to model [[Diffusion Calculations\|diffusion]]. Because they share same methods, a simulation can activate poroelasticity (with above commands) or diffusion (with comparable [[Diffusion Calculations\|Diffusion commands]]), but cannot activate them both. Any simulation, however, can combine poroelasticity or diffusion with [[Thermal Calculations\|thermal calculations and conduction]]. Note that when choosing [[MPM Input Files#Archiving Results\|archiving options]], the terms "concentration" and "porepressure" are synonyms or either can be used and the archiving will store concentration terms for [[Diffusion Calculations\|diffusion calculations]] or pore pressure terms for poroelasticity calculations.		Note that poroelasticity models fluid transport through materials by transport methods nearly identical to those used to model [[Diffusion Calculations\|diffusion]]. Because they share same methods, a simulation can activate poroelasticity (with above commands) or diffusion (with comparable [[Diffusion Calculations\|Diffusion commands]]), but cannot activate them both. Any simulation, however, can combine poroelasticity or diffusion with [[Thermal Calculations\|thermal calculations and conduction]]. Note that when choosing [[MPM Input Files#Archiving Results\|archiving options]], the terms "concentration" and "porepressure" are synonyms or either can be used and the archiving will store concentration terms for [[Diffusion Calculations\|diffusion calculations]] or pore pressure terms for poroelasticity calculations.

Nairnj: /* Activating Poroelasticity */

2021-01-01T19:09:48Z

Activating Poroelasticity

← Older revision		Revision as of 19:09, 1 January 2021
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	* <tt>(p0)</tt>is reference pore pressure (in [[ConsistentUnits Command#Legacy and Consistent Units\|pressure units]]). The default <tt>(p0)</tt> is 0. Unless changed, all particles will be initialized to start at the reference pore pressure.		* <tt>(p0)</tt>is reference pore pressure (in [[ConsistentUnits Command#Legacy and Consistent Units\|pressure units]]). The default <tt>(p0)</tt> is 0. Unless changed, all particles will be initialized to start at the reference pore pressure.
	* <tt>(eta)</tt> is fluid viscosity for fluid in the pores (and same for all materials). Default is 1 cP in Legacy units or 1 [[ConsistentUnits Command#Legacy and Consistent Units\|viscosity unit]] in consistent units (note that Legacy units default to water viscosity, but consistent units default to 1 [[ConsistentUnits Command#Legacy and Consistent Units\|viscosity unit]] which may not be water viscosity - it is therefore best to always enter this viscosity and not rely on default setting being for water).		* <tt>(eta)</tt> is fluid viscosity for fluid in the pores (and same for all materials). Default is 1 cP in Legacy units or 1 [[ConsistentUnits Command#Legacy and Consistent Units\|viscosity unit]] in consistent units (note that Legacy units default to water viscosity, but consistent units default to 1 [[ConsistentUnits Command#Legacy and Consistent Units\|viscosity unit]] which may not be water viscosity - it is therefore best to always enter this viscosity and not rely on default setting being for water).

			By default, poroelasticity uses update methods analogous to FLIP methods used in mechanics. This update, however, sometimes results in pore pressure oscillations on particles within one cell. Poroelasticity simulations with oscillations can be improved by using [[PeriodicXPIC Custom Task#Using FMPM(k) For Transport Properties\|periodic FMPM(k)]] for poroelasticity updates. In fact, because poroelasticity is inherently stiffer then conduction or diffusion, it may require FMPM(k) for stable simulations.

	Note that poroelasticity models fluid transport through materials by transport methods nearly identical to those used to model [[Diffusion Calculations\|diffusion]]. Because they share same methods, a simulation can activate poroelasticity (with above commands) or diffusion (with comparable [[Diffusion Calculations\|Diffusion commands]]), but cannot activate them both. Any simulation, however, can combine poroelasticity or diffusion with [[Thermal Calculations\|thermal calculations and conduction]]. Note that when choosing [[MPM Input Files#Archiving Results\|archiving options]], the terms "concentration" and "porepressure" are synonyms or either can be used and the archiving will store concentration terms for [[Diffusion Calculations\|diffusion calculations]] or pore pressure terms for poroelasticity calculations.		Note that poroelasticity models fluid transport through materials by transport methods nearly identical to those used to model [[Diffusion Calculations\|diffusion]]. Because they share same methods, a simulation can activate poroelasticity (with above commands) or diffusion (with comparable [[Diffusion Calculations\|Diffusion commands]]), but cannot activate them both. Any simulation, however, can combine poroelasticity or diffusion with [[Thermal Calculations\|thermal calculations and conduction]]. Note that when choosing [[MPM Input Files#Archiving Results\|archiving options]], the terms "concentration" and "porepressure" are synonyms or either can be used and the archiving will store concentration terms for [[Diffusion Calculations\|diffusion calculations]] or pore pressure terms for poroelasticity calculations.

Nairnj: /* Poroelasticity Boundary Conditions */

2018-12-13T00:21:49Z

Poroelasticity Boundary Conditions

← Older revision		Revision as of 00:21, 13 December 2018
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	<math>dp = {K\over K_u} Q dv_F</math>		<math>dp = {K\over K_u} Q dv_F</math>

	A more involved relation in needed to get dp from dv<sub>F</sub> for anisotropic ~~simulations~~. In typical simulations, the volume fraction flux is small (much less than one when multiplied by particle area) and can be adjusted to get desired pore pressure changes.		A more involved relation in needed to get dp from dv<sub>F</sub> for anisotropic materials. In typical simulations, the volume fraction flux is small (much less than one when multiplied by particle area) and can be adjusted to get desired pore pressure changes.

	== References ==		== References ==

	<references/>		<references/>

Nairnj: /* Poroelasticity Boundary Conditions */

2018-12-13T00:21:15Z

Poroelasticity Boundary Conditions

← Older revision		Revision as of 00:21, 13 December 2018
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	Note that setting initial particle pore pressure different than the reference pore pressure will cause strains to immediately evolve toward the changed state. The net effect will be an instantaneous "impact" of pore pressure change that might cause undesirable dynamic effects.		Note that setting initial particle pore pressure different than the reference pore pressure will cause strains to immediately evolve toward the changed state. The net effect will be an instantaneous "impact" of pore pressure change that might cause undesirable dynamic effects.

	Also note that pore pressure flux is set by specifying a flux for volume fraction of pore fluid in the solid. A change in fluid volume fraction will translate into a change in pore pressure. In the absence of Darcy's flow away form the particle, an estimated change in pore pressure, dp, due to chance in pore fluid volume fraction, dv<sub>F</sub> is:		Also note that pore pressure flux is set by specifying a flux for volume fraction of pore fluid in the solid. A change in fluid volume fraction will translate into a change in pore pressure. In the absence of Darcy's flow away form the particle, an estimated change in pore pressure, dp, due to chance in pore fluid volume fraction, dv<sub>F</sub> for an isotropic material is:

← Older revision		Revision as of 19:11, 1 January 2021
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	* <tt>(eta)</tt> is fluid viscosity for fluid in the pores (and same for all materials). Default is 1 cP in Legacy units or 1 [[ConsistentUnits Command#Legacy and Consistent Units\|viscosity unit]] in consistent units (note that Legacy units default to water viscosity, but consistent units default to 1 [[ConsistentUnits Command#Legacy and Consistent Units\|viscosity unit]] which may not be water viscosity - it is therefore best to always enter this viscosity and not rely on default setting being for water).		* <tt>(eta)</tt> is fluid viscosity for fluid in the pores (and same for all materials). Default is 1 cP in Legacy units or 1 [[ConsistentUnits Command#Legacy and Consistent Units\|viscosity unit]] in consistent units (note that Legacy units default to water viscosity, but consistent units default to 1 [[ConsistentUnits Command#Legacy and Consistent Units\|viscosity unit]] which may not be water viscosity - it is therefore best to always enter this viscosity and not rely on default setting being for water).

	By default, poroelasticity uses update methods analogous to FLIP methods used in mechanics. This update, however, sometimes results in pore pressure oscillations on particles within one cell. Poroelasticity simulations with oscillations can be improved by using [[PeriodicXPIC Custom Task#Using FMPM(k) For Transport Properties\|periodic FMPM(k)]] for poroelasticity updates. In fact, because poroelasticity is inherently stiffer then conduction or diffusion, it may require FMPM(k) for stable simulations.		By default, poroelasticity uses update methods analogous to FLIP methods used in mechanics. This update, however, sometimes results in pore pressure oscillations on particles within one cell. Poroelasticity simulations with oscillations can be improved by using [[PeriodicXPIC Custom Task#Using FMPM(k) For Transport Properties\|periodic FMPM(k)]] for poroelasticity updates. In fact, because poroelasticity is inherently stiffer then [[Thermal Calculations\|conduction]] or [[Diffusion Calculations\|diffusion]], it may require FMPM(k) for stable simulations.

	Note that poroelasticity models fluid transport through materials by transport methods nearly identical to those used to model [[Diffusion Calculations\|diffusion]]. Because they share same methods, a simulation can activate poroelasticity (with above commands) or diffusion (with comparable [[Diffusion Calculations\|Diffusion commands]]), but cannot activate them both. Any simulation, however, can combine poroelasticity or diffusion with [[Thermal Calculations\|thermal calculations and conduction]]. Note that when choosing [[MPM Input Files#Archiving Results\|archiving options]], the terms "concentration" and "porepressure" are synonyms or either can be used and the archiving will store concentration terms for [[Diffusion Calculations\|diffusion calculations]] or pore pressure terms for poroelasticity calculations.		Note that poroelasticity models fluid transport through materials by transport methods nearly identical to those used to model [[Diffusion Calculations\|diffusion]]. Because they share same methods, a simulation can activate poroelasticity (with above commands) or diffusion (with comparable [[Diffusion Calculations\|Diffusion commands]]), but cannot activate them both. Any simulation, however, can combine poroelasticity or diffusion with [[Thermal Calculations\|thermal calculations and conduction]]. Note that when choosing [[MPM Input Files#Archiving Results\|archiving options]], the terms "concentration" and "porepressure" are synonyms or either can be used and the archiving will store concentration terms for [[Diffusion Calculations\|diffusion calculations]] or pore pressure terms for poroelasticity calculations.

← Older revision		Revision as of 19:09, 1 January 2021
Line 22:		Line 22:
	* <tt>(p0)</tt>is reference pore pressure (in [[ConsistentUnits Command#Legacy and Consistent Units\|pressure units]]). The default <tt>(p0)</tt> is 0. Unless changed, all particles will be initialized to start at the reference pore pressure.		* <tt>(p0)</tt>is reference pore pressure (in [[ConsistentUnits Command#Legacy and Consistent Units\|pressure units]]). The default <tt>(p0)</tt> is 0. Unless changed, all particles will be initialized to start at the reference pore pressure.
	* <tt>(eta)</tt> is fluid viscosity for fluid in the pores (and same for all materials). Default is 1 cP in Legacy units or 1 [[ConsistentUnits Command#Legacy and Consistent Units\|viscosity unit]] in consistent units (note that Legacy units default to water viscosity, but consistent units default to 1 [[ConsistentUnits Command#Legacy and Consistent Units\|viscosity unit]] which may not be water viscosity - it is therefore best to always enter this viscosity and not rely on default setting being for water).		* <tt>(eta)</tt> is fluid viscosity for fluid in the pores (and same for all materials). Default is 1 cP in Legacy units or 1 [[ConsistentUnits Command#Legacy and Consistent Units\|viscosity unit]] in consistent units (note that Legacy units default to water viscosity, but consistent units default to 1 [[ConsistentUnits Command#Legacy and Consistent Units\|viscosity unit]] which may not be water viscosity - it is therefore best to always enter this viscosity and not rely on default setting being for water).

			By default, poroelasticity uses update methods analogous to FLIP methods used in mechanics. This update, however, sometimes results in pore pressure oscillations on particles within one cell. Poroelasticity simulations with oscillations can be improved by using [[PeriodicXPIC Custom Task#Using FMPM(k) For Transport Properties\|periodic FMPM(k)]] for poroelasticity updates. In fact, because poroelasticity is inherently stiffer then conduction or diffusion, it may require FMPM(k) for stable simulations.

	Note that poroelasticity models fluid transport through materials by transport methods nearly identical to those used to model [[Diffusion Calculations\|diffusion]]. Because they share same methods, a simulation can activate poroelasticity (with above commands) or diffusion (with comparable [[Diffusion Calculations\|Diffusion commands]]), but cannot activate them both. Any simulation, however, can combine poroelasticity or diffusion with [[Thermal Calculations\|thermal calculations and conduction]]. Note that when choosing [[MPM Input Files#Archiving Results\|archiving options]], the terms "concentration" and "porepressure" are synonyms or either can be used and the archiving will store concentration terms for [[Diffusion Calculations\|diffusion calculations]] or pore pressure terms for poroelasticity calculations.		Note that poroelasticity models fluid transport through materials by transport methods nearly identical to those used to model [[Diffusion Calculations\|diffusion]]. Because they share same methods, a simulation can activate poroelasticity (with above commands) or diffusion (with comparable [[Diffusion Calculations\|Diffusion commands]]), but cannot activate them both. Any simulation, however, can combine poroelasticity or diffusion with [[Thermal Calculations\|thermal calculations and conduction]]. Note that when choosing [[MPM Input Files#Archiving Results\|archiving options]], the terms "concentration" and "porepressure" are synonyms or either can be used and the archiving will store concentration terms for [[Diffusion Calculations\|diffusion calculations]] or pore pressure terms for poroelasticity calculations.