《基础工程》课程PPT教学课件（英文讲稿）Chapter 10 Single Piles（2/2）

Chapter 10 Single Piles Static Capacity and Lateral Loads;Pile/Pole Buckling

Chapter 10 Single Piles Static Capacity and Lateral Loads;Pile/Pole Buckling

10.1 Introduction What's piles-Piles are structual members of timber, concrete,and/or steel that are used to transmit surface loads to lower levels in the soil mass. How pile transmit loads-by skin (or side)friction (resistance)and point (or end)resistance. Skin (or side)friction (resistance)-vertical distribution of the load along the pile shaft Point (or end)resistance-direct application of load to a lower stratum throught the pile point

10.1 Introduction ◼ What’s piles-Piles are structual members of timber, concrete, and/or steel that are used to transmit surface loads to lower levels in the soil mass. ◼ How pile transmit loads-by skin (or side) friction (resistance) and point (or end) resistance. ◼ Skin (or side) friction (resistance)-vertical distribution of the load along the pile shaft ◼ Point (or end) resistance-direct application of load to a lower stratum throught the pile point

10.1 Introduction Piles may be classified based on: the load transmit-friction (or floating)pile and point, or end-bearing pile. The material of pile-concrete pile,timber pile,steel pile and composite pile The installation of pile-precast concrete pile,cast-in- place concrete pile and prestress concrete pile The inserted method of pile-driving with blows, driving using a vibratory device,jacking and drilling a hole and inserting a pile into it

10.1 Introduction ◼ Piles may be classified based on: ◼ the load transmit-friction (or floating) pile and point, or end-bearing pile. ◼ The material of pile-concrete pile, timber pile, steel pile and composite pile ◼ The installation of pile-precast concrete pile, cast-in￾place concrete pile and prestress concrete pile ◼ The inserted method of pile-driving with blows, driving using a vibratory device, jacking and drilling a hole and inserting a pile into it

10.1 Introduction Suitable conditions of piles: -to carry the superstructure loads(both vertical and lateral loads)into or throught a soil stratum. -to resist uplift,or overturning,forces -to compact loose,cohesionless deposits. -to control settlements. -to stiffen the soil beneath machine foundation. -to protect bridge abutment when scour occur. -to tranmit loads above the water surface through the water and into the underlying soil in offshore construction. -to control earth movement(for example,landslide). -to penetrate below a soil layer that swells or consolidation

10.1 Introduction ◼ Suitable conditions of piles: ◼ -to carry the superstructure loads (both vertical and lateral loads) into or throught a soil stratum. ◼ -to resist uplift, or overturning, forces. ◼ -to compact loose, cohesionless deposits. ◼ -to control settlements. ◼ -to stiffen the soil beneath machine foundation. ◼ -to protect bridge abutment when scour occur. ◼ -to tranmit loads above the water surface through the water and into the underlying soil in offshore construction. ◼ -to control earth movement (for example, landslide). ◼ -to penetrate below a soil layer that swells or consolidation

10.2 Concrete Piles Conrete piles may be precast,prestressed,cast in place,or of composite construction. Precast concrete piles-piles are formed in a central casting yard to the specified length,cured,and then shipped to the construction site. -precast piles may be made using ordinary reinforcement or they may be prestressed. ■ -using ordinary reinforcement are designed to resist bending stresses during pickup and transport to the site and bending moments from lateral loads and to provide sufficient resistance to vertical loads and any tension forces developed during driving. -the minimum pile reinforcement should be 1 percent. -bending moments developed during pickup depending on the location of the pickup point

10.2 Concrete Piles ◼ Conrete piles may be precast, prestressed, cast in place, or of composite construction. ◼ Precast concrete piles-piles are formed in a central casting yard to the specified length, cured, and then shipped to the construction site. ◼ -precast piles may be made using ordinary reinforcement or they may be prestressed. ◼ -using ordinary reinforcement are designed to resist bending stresses during pickup and transport to the site and bending moments from lateral loads and to provide sufficient resistance to vertical loads and any tension forces developed during driving. ◼ -the minimum pile reinforcement should be 1 percent. ◼ -bending moments developed during pickup depending on the location of the pickup point

10.2 Concrete Piles Prestressed piles are formed by tensioning high-strength steel prestress cables to a value on the order of 0.5 to 0.7fuit,and casting the concrete pile about the cable.When the concrete hardens,the prestress cables are cut,with the tension force in the cables now producing a compressive stress in the concrete piles as the steel attempts to return to its unstretched length

10.2 Concrete Piles ◼ Prestressed piles are formed by tensioning high-strength steel prestress cables to a value on the order of 0.5 to 0.7fult, and casting the concrete pile about the cable. When the concrete hardens, the prestress cables are cut, with the tension force in the cables now producing a compressive stress in the concrete piles as the steel attempts to return to its unstretched length

10.2 Concrete Piles A cast-in-place pile is formed by drilling a hole in the ground and filling it with concrete. The hole may be drilled,excavated,or formed by driving a shell or casing into the ground. The casing may be driven using a mandrel,after which withdrawal of the mandrel empties the casing. The casing may be driven with a driving tip on the point,providing a shell that is ready for filling with concrete immediately. The casing may be driven open-end,the soil entrapped in the casing being jetted out after the drilling is completed

10.2 Concrete Piles ◼ A cast-in-place pile is formed by drilling a hole in the ground and filling it with concrete. ◼ The hole may be drilled, excavated, or formed by driving a shell or casing into the ground. ◼ The casing may be driven using a mandrel, after which withdrawal of the mandrel empties the casing. ◼ The casing may be driven with a driving tip on the point, providing a shell that is ready for filling with concrete immediately. ◼ The casing may be driven open-end, the soil entrapped in the casing being jetted out after the drilling is completed

10.2 Concrete Piles The commonly available patented cast-in- place piles are basically of three types: ■(1)shell or cased (2)shell-less (uncased) (3)pedestal type The uncased pile can be formed by using a hollowstem continuous-flight auger The pedestal pile can be formed by Franki's method

10.2 Concrete Piles ◼ The commonly available patented cast-in￾place piles are basically of three types: ◼ (1) shell or cased ◼ (2) shell-less (uncased) ◼ (3) pedestal type ◼ The uncased pile can be formed by using a hollowstem continuous-flight auger ◼ The pedestal pile can be formed by Franki’s method

10.3 Steel Piles The types of steel pile: -rolled HP shapes -pipe piles ■-wide-flange beams -standard W and I shapes In the HP pile the flanges and web are of equal thickness. The standard W and I shapes usually have a thinner web than flange. Pipe piles are either welded or seamless steel pipes, which may be driven either open-end or closed-end

10.3 Steel Piles ◼ The types of steel pile: ◼ -rolled HP shapes ◼ -pipe piles ◼ -wide-flange beams ◼ -standard W and I shapes ◼ In the HP pile the flanges and web are of equal thickness. ◼ The standard W and I shapes usually have a thinner web than flange. ◼ Pipe piles are either welded or seamless steel pipes, which may be driven either open-end or closed-end

10.3 Steel Piles The HP pile and open-end pipe are small- volume displacement pile. HP piles have an advantage of sufficient rigidity. Open-end pipe piles have the advantage of surface entry to break up boulders encountered by either use of a chopping bit or drilling,blasting,and removal of the rock fragments. Splices in steel piles are made by welding or by bolting

10.3 Steel Piles ◼ The HP pile and open-end pipe are small￾volume displacement pile. ◼ HP piles have an advantage of sufficient rigidity. ◼ Open-end pipe piles have the advantage of surface entry to break up boulders encountered by either use of a chopping bit or drilling, blasting, and removal of the rock fragments. ◼ Splices in steel piles are made by welding or by bolting