Porous displacement piles meeting filter design criteria for rapid consolidation and densification of subsurface soils and intermediate geomaterials

A porous displacement pile for rapid consolidation and densification of various layers of soils and intermediate geomaterials in a soil deposit, the porous displacement pile comprising:

• (i) driving first a non-displacement pipe pile comprising a hollow pipe section into ground;
• (ii) driving a closed-ended displacement porous pipe pile comprising a closed-ended pipe section with very small holes and/or very narrow slots or comprising a closed-ended sintered porous pile through inside of the non-displacement pipe pile into the ground to a design depth;
• (iii) the closed ended pipe pile with the very small holes and/or very narrow slots should not to let in-situ soil particles penetrate into the holes or slots during driving it into the ground and should have required filtration capacity;
• (iv) the filtration capacity of the closed ended pipe pile with the very small holes and/or very narrow slots and the closed-ended sintered porous pipe pile to be checked by a laboratory test to verify whether the said pipe piles can provide free flow of pressurized water and prevent migration of the in-situ soil into it;
• (v) modifying an existing laboratory test apparatus by (a) representing the closed ended pipe section with the very small holes and/or very narrow slots by a porous plate comprising holes/slots of same size as of the closed ended pipe section with the very small holes and/or very narrow slots, (b) attaching the circular ring to inside a test chamber wall, (c) placing the said porous plate on a circular ring which is water-sealed by use of an adhesive sealant, (c) compacting base soil comprising of the in-situ soil in layers to a density at same moisture content as of the in-situ soil on top of the said porous plate, and (d) filling the spaces in the test chamber of the laboratory test apparatus in spaces above the base soil and below the said porous plate by gravel;
• (vi) the porous displacement pile comprising the closed-ended pipe section with the very small holes and/or slots and the closed-ended sintered porous pile to be used as the porous displacement pile if drivable by a pile drivable hammer into the in-situ soil without exceeding allowable driving stresses;
• (vii) the porous displacement pile after being driven into the ground occupies space previously occupied by in-situ cohesive soil and develops excess pore-water pressures in saturated cohesive soil and a combination of the excess pore-water pressures and excess pore-air pressures in partially saturated cohesive soil, by pressurizing the pore-water and pore-air present in the pores of the cohesive soil;
• (viii) the excess pore-water pressures and the pore-air pressures developed in the in-situ cohesive soil are rapidly dissipated by flow of the pressurized pore-water and pore-air through the porous displacement pile to the ground surface or to sandy layer located within the ground, thereby rapidly consolidating and densifying subsurface layers comprising the in-situ cohesive soil;
• (ix) wherein the excess pore-water pressures do not develop in sandy soil and if develop, dissipate immediately during driving of the porous displacement piles;
• (x) driving the porous displacement piles in a grid pattern densifies the sandy soil instantly;
• (xi) installing a plurality of the porous displacement pile spaced apart in a grid pattern vertically and/or at a batter in an area requiring densification of one subsurface layer or several subsurface layers of soils and intermediate geomaterials of the soil deposit.

A porous displacement pile for rapid consolidation and densification of various layers of soils and intermediate geomaterials in a soil deposit, the porous displacement pile comprising:

• (i) driving first a non-displacement pile comprising a hollow pipe section into ground;
• (ii) driving a precast prestressed porous concrete pile through inside of the non-displacement pipe pile into the ground to a design depth;
• (iii) the prestressed porous concrete should not to let in-situ soil particles penetrate into the porous concrete during driving it into the ground and should have adequate filtration capacity;
• (iv) the filtration capacity of the prestressed porous concrete pile to be checked by a laboratory test to verify whether the precast prestressed porous concrete pile can provide free flow of pressurized pore-water and prevent migration of the in-situ soil into it;
• (v) modifying an existing laboratory test apparatus by (a) representing the precast prestressed porous concrete pile by a porous concrete plate comprising porous concrete of the same mix design and porosity as that of the porous concrete of the precast prestressed porous concrete pile, (b) attaching the circular ring to inside a test chamber wall, (c) placing the porous concrete plate on a circular ring which is water-sealed by use of an adhesive sealant, (c) compacting base soil comprising of the in-situ soil in layers to a density at same moisture content as of the in-situ soil on top of the porous concrete plate, and (d) filling the spaces in the test chamber of the laboratory test apparatus in spaces above the base soil and below the porous concrete plate by gravel;
• (vi) the porous displacement pile comprising the prestressed concrete pile to be used as the porous displacement pile if drivable by a pile drivable hammer into the in-situ soil without exceeding allowable driving stresses;
• (vii) the porous displacement pile after being driven into the ground occupies space previously occupied by in-situ cohesive soil and develops excess pore-water pressures in saturated cohesive soil and a combination of the excess pore-water pressures and excess pore-air pressures in partially saturated cohesive soil, by pressurizing the pore-water and pore-air present in the pores of the cohesive soil;
• (viii) the excess pore-water pressures and the pore-air pressures developed in the in-situ cohesive soil are rapidly dissipated by flow of the pressurized pore-water and pore-air through the porous displacement pile to the ground surface or to sandy layer located within the ground, thereby rapidly consolidating and densifying subsurface layers comprising the in-situ cohesive soil;
• (ix) wherein the excess pore-water pressures do not develop in sandy soils and if develop, dissipate immediately during driving of the porous displacement piles;
• (x) driving the porous displacement piles in a grid pattern to densify the subsurface layers of the sandy soils instantly;
• (xi) installing a plurality of the porous displacement pile spaced apart in a grid pattern vertically and/or at a batter in an area requiring densification of one subsurface layer or several subsurface layers of soils and intermediate geomaterials of the soil deposit.