Pile Design and Construction Practice, Fifth edition

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Longitudinal reinforcement is provided in the piles to the extent necessary to carry vertical loading, eccentric loads from the underpinning bearers, and lateral loading from earth and hydrostatic pressure. Screw or helical piles comprising solid square shafts up to 60 mm and tubular shafts up to 90 mm with helical plates between 200 and 350 mm diameter attached at intervals along the shaft, such as the AB Chance systems and ScrewFast Foundations in the UK, are effective as underpinning support. They are screwed into the ground adjacent to the foundation using rotary drives, either attached to hydraulic excavators with torque capacity up to 68 kNm or hand-held units with around 3 kNm torque – resisted by a torque bar. The bearing capacity is related to the area of the helical plates, four plates being typical and spaced so that overlap of bearing zones does not occur. Shaft friction is not usually applied unless the shaft diameter is greater than 90 mm. As for the slender steel-jacked piers above, buckling has to be considered and corrosion protection provided (note this form of slender pile should not be confused with the large-diameter displacement pile formed by screwing a mandrel into the ground – see Section 2.3.5). 9.3 Piling in mining subsidence areas Miscellaneous piling problems 445 The form in which subsidence takes place after extracting minerals by underground mining depends on the particular technique used in the mining operations. In Great Britain the problems of subsidence mainly occur in coal-mining areas where the practice in the remaining working collieries is to extract the coal by ‘longwall’ methods. Using this technique the entire coal seam is removed from a continuously advancing face. The roof of the workings behind the face is supported by multiple rows of hydraulically operated props. As the face moves forward the props in the rear are systematically lowered to allow the roof of the workings to sink down onto heaps of mine dirt or ‘stowage’. The overlying rock strata and over-burden soil follow the downward movement of the roof and the consequent subsidence of the ground surface is in the form of a wave which advances parallel to and at approximately the same rate as the advancing coal face. The subsidence is accompanied by very substantial horizontal strains of the ground surface, these strains being tensile at the crest of the wave and compressive at the trough and thus taking the form shown in Figure 9.9. Tension 0 500 1000 1500 2000 Subsidence (mm) Subsidence curve Worked-out seam Compression Limit angle Figure 9.9 Profile of ground subsidence over longwall mine workings. +0.004 +0.002 0 –0.002 –0.004 Strain Unworked coal Ground surface
446 Miscellaneous piling problems The magnitude of the strain can range from as much as plus or minus 0.8% of the overburden thickness above shallow workings to 0.2% over deep seams. The horizontal ground movements make it virtually impossible to use piled foundations in areas where longwall mining is proposed, or is currently being practised. The horizontal shearing forces accompanying the strains are so high that it is quite uneconomical to attempt to resist them by heavily strengthening the pile shafts. However, in areas where subsidence following longwall mining has virtually ceased it is possible to use piled foundations if it is recognized that some residual movement will take place as the collapsed strata slowly reach final equilibrium. In these cases it is desirable to terminate piles in a soil layer overlying rockhead, as shown on the left-hand side of Figure 9.10. The soil acts as a cushion, preventing any concentration of load on the broken rock strata. Long-term movements may be substantial near the boundary of the worked-out seam. If the workings are shallow, piles may be taken down through the collapsed overburden to intact rock layers below the coal seam as shown on the right-hand side of Figure 9.10. Bored and cast-in-place piles are used for this purpose, but it is essential to isolate the shaft of the pile from the overburden above the coal seam in order to avoid heavy compressive loading caused by downdrag from the collapsing strata. This isolation is achieved by placing the concrete within a shell formed from stiffened light-gauge steel sheeting, the sheeting terminating at the base of the coal seam. Below this level the concrete can be cast against the surface of the stable strata to form a ‘rock socket’, as shown in Figure 9.11. The space between the shell and the wall of the drill hole through the overburden can be filled with bentonite slurry, soft bitumen or loosely placed rock fragments. A minimum clearance of 150 mm should be provided to accommodate minor Piling Collapsed over burden Subsidence complete Very soft clay Stiff boulder clay Stowage Long-continuing small subsidence Unworked seam No subsidence Figure 9.10 Piling through collapsed ground over longwall mine workings.
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Pile Design and Construction Practi
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Pile Design and Construction Practi
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Contents Preface to fifth edition i
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7.3 Designing piles to resist drivi
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Preface to fifth edition Piling rig
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Preface to fifth edition xi Pearson
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Chapter 1 General principles and pr
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(a) Backfill Bulb of pressure Appli
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are allowed to be used by Eurocode
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application of different load facto
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Load transfer The contractor’s gu
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(7) Jacked-down steel tube with clo
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Types of pile 13 needed to avoid cr
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(a) (b) Precast concrete Head of ti
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Table 2.2 Modification factor K 2 b
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4d d 10 mm M.S. plate sleeve tarred
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Table 2.3 Working loads and maximum
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Cement content �300 kg/m3 �325
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Types of pile 25 Table 2.5 BS 8004
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(a) (b) (c) (d) Cast iron or cast s
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Sheathing Bottom boards Figure 2.9
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Misplaced bearers Lifting holes Cra
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Section Bayonet plug Plan Locking p
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Existing foundation Precast pile ca
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Types of pile 37 Where very long le
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Types of pile 39 rotate during driv
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Types of pile 41 Because of their r
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(a) (b) Types of pile 43 Figure 2.2
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(a) (b) Welds Welds Types of pile 4
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(a) M.S. plate shoe Welds (b) 2.2.6
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Types of pile 49 brittle fracture r
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(a) (b) (c) Hammer Driving tube Con
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Types of pile 53 all cast-in-place
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Figure 2.28 The TaperTube pile.
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(a) (b) Figure 2.29 (a) The ScrewSo
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Types of pile 59 The simplest form
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Types of pile 61 Transverse reinfor
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Types of pile 63 completion the res
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Types of pile 65 permanently in the
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Types of pile 67 (3) Construction o
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Types of pile 69 can withstand fair
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Chapter 3 Piling equipment and meth
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Piling equipment and methods 73 A r
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Maximum height 26.32 m Usable leade
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Figure 3.4 Liebherr LRH 400 48 m lo
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Piling equipment and methods 79 the
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Piling frame Single-acting hammer S
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Guides for engaging leaders Steam o
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Table 3.1 Characteristics of some s
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Table 3.2 Characteristics of some h
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Piling equipment and methods 89 Tab
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Table 3.4 Characteristics of some d
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Figure 3.16 Driving a pile casing w
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Table 3.5 Continued Piling equipmen
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Soil resistance to driving (MN) 25
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Figure 3.19 Noise-abatement tower u
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Dolly M.S. plate Plastics Hardwood
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Standard elbow bend Detachable scre
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Figure 3.24 Discharging concrete in
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Piling equipment and methods 107 Fi
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Table 3.6 Continued Piling equipmen
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Figure 3.30 Top-hinged under-reamin
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Rotary table Hydraulic motor Water
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Piling equipment and methods 121 sl
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Pile head Pile base 2 holes ∅ 4 m
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Piling equipment and methods 125 Ca
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Piling equipment and methods 127 sm
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Piling equipment and methods 131 Th
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Piling equipment and methods 133 th
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Piling equipment and methods 135 Pi
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Piling equipment and methods 137 ve
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Chapter 4 Calculating the resistanc
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O C Settlement A Reloading Load B U
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Resistance of piles to compressive
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for spread foundations in various c
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structural actions and A2 to geotec
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Geometrical data are concerned with
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Figure 4.3 Failure surfaces for com
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Depth below ground level in m 5.6 1
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(a) (b) Peak adhesion factor a p Le
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orehole or test profile over the pe
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Effective length Shaft friction not
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4.3 Piles in coarse-grained soils 4
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Depth below ground surface (m) Resi
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Depth of penetration (m) 0 0 5 10 1
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using standard penetration tests or
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� � Resistance of piles to comp
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Safety factors generally used in th
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Depth to NAP datum (m) Cone resista
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The conditions at the interface can
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The shear modulus G in equation 4.3
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2.0 OD tubular steel pile with clos
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where Resistance of piles to compre
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eached the point of ultimate resist
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(4) Obtain the safe end-bearing loa
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Vertical force, t t-z curve Vertica
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where the bearing capacity factor:
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and RQD of the rock as shown in Tab
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Depth below ground level (m) 0 5 10
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settlement of the pile are summariz
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Rock socket reduction factor a 1.0
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Table 4.17 � and � values of we
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Influence factor, l p 2.0 1.6 1.2 0
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(a) (b) No load on pile head Residu
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a closed end into a deep deposit of
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Average shearing strength along pil
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It is assumed that the shear streng
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Depth below ground level (m) Figure
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Figure 4.45 Depth below ground leve
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Depth of h(m) Segment (m bql) � h
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For a wall thickness of 19 mm in mi
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Pile groups under compressive loadi
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24.0 m 16.0 m The comparative group
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where c � cohesion intercept of s
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Inclination factor, i c Inclination
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z/B 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
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Compressive stress 1.5 q n q n B A
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E u/c u 3000 2500 2000 1500 1000 50
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0 0 1 2 3 4 H/B 5 6 7 8 9 0 1 2 3 4
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D LB LB D 0.50 0 0.1 0.2 0.3 0.4 0.
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Initial tangent constrained modulus
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factor N for which Schmertmann sugg
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0 0 2 4 H/B 6 8 10 Influence factor
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Overall loading 100 kN/m2 (a) (b) (
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(a) (b) (c) (d) Pile groups under c
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Depth below ground level in m 5 10
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For the arrangement of the piles sh
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Soft clay Sand B/2 5 11.2 m Figure
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Unit negative skin friction at top
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Chapter 6 The design of piled found
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(a) Tie rod Wholly compression Whol
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esistance of cylindrical augered fo
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in the ground is assumed to be equa
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Section 3.3.1. Enlargements cannot
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Piles to resist uplift and lateral
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Spacer Top of hard rock Drilling pi
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where m is the modular ratio of ste
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Table 6.3 Examples of bond stress b
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Top of rock 30˚ 30˚ Figure 6.15 F
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(b) P/n & �Vm Vc 2.0 1.8 1.6 1.4
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Table 6.4 Partial resistance factor
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and adjustment, starting with a ver
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Coefficient of subgrade modulus var
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where e is the height from the grou
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and Thus from Figure 6.24 deflectio
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(a) Deflection coefficient Ay (c) D
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(a) (b) (c) Depth coefficient Z 0 1
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Horizontal load H; Bending moment =
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Methods of drawing sets of p-y curv
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Calculations to determine the ultim
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(a) (b) Pressure Soil reaction p Ps
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Z�x/R 0 1.0 2.0 3.0 4.0 5.0 M(z)
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(a) yroGc H0 Ep Gc 1/7 (b) 0 0 0.1
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(a) determining the compressive and
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A X Z B R A Resultant R R B Y C D R
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6.8 FREEMAN, C. F., KLAJNERMAN, D.,
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Thus the load to be carried by anch
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If high-tensile steel (which has a
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sustained horizontal load which can
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Calculating the allowable horizonta
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Pile cap (Weight�2475 kN) F E D C
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The resultant of the vertical and h
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The Brinch Hansen bearing capacity
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Modulus of elasticity of pile � 2
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Chapter 7 Some aspects of the struc
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(a) (b) (c) Lifting rope Lifting po
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7.3 Designing piles to resist drivi
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Structural design of piles and pile
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Structural design of piles and pile
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should not arise if the piles are d
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(a) (b) (c) M.S.plate cover M.S.cap
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45˚ Structural design of piles and
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X Column Y9 Y9 Y Critical section f
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7.9 The design of pile capping beam
Page 410 and 411: Damp-proof course Cranked vent Grou
Page 412 and 413: Structural design of piles and pile
Page 414 and 415: (a) (b) Deck of wharf Fender Rubber
Page 416 and 417: (a) (b) y y e z f A The bending mom
Page 418 and 419: Piling for marine structures 403 th
Page 420 and 421: Pipe trunkways Hose handling platfo
Page 422 and 423: Piling for marine structures 407 8.
Page 424 and 425: Piling for marine structures 409 sh
Page 426 and 427: In SI units, equation 8.8 becomes f
Page 428 and 429: The natural frequency of the member
Page 430 and 431: The empirical equation of Korzhavin
Page 432 and 433: Piling for marine structures 417 re
Page 434 and 435: Table 8.3 Minimum safety factors fo
Page 436 and 437: Piling for marine structures 421 th
Page 438 and 439: Piling for marine structures 423 sh
Page 440 and 441: 8.21 GERWICK, B. C. Construction of
Page 442 and 443: Soil resistance p in kN per m of de
Page 444 and 445: From Figures 6.29a and b the comput
Page 446 and 447: giving 9.7y � 0.26, y � 0.26
Page 448 and 449: From �7.5 to �3.0 m: no increas
Page 450 and 451: Miscellaneous piling problems 435 W
Page 452 and 453: 9.2 Piling for underpinning Miscell
Page 454 and 455: Miscellaneous piling problems 439 B
Page 456 and 457: Miscellaneous piling problems 441 T
Page 458 and 459: Miscellaneous piling problems 443 p
Page 462 and 463: Light-gauge steel lining tubes Stow
Page 464 and 465: When inspecting the geological cond
Page 466 and 467: Miscellaneous piling problems 451 f
Page 468 and 469: natural ‘freeze-back’ around th
Page 470 and 471: Miscellaneous piling problems 455 b
Page 472 and 473: Miscellaneous piling problems 457 w
Page 474 and 475: Drainage layer 8.0 m 6.0 m Fill 1.0
Page 476 and 477: p m/c u 10.5 2p 0 and the mean hori
Page 478 and 479: Bridge abutment support piles Emban
Page 480 and 481: Figure 9.23 Drilling equipment for
Page 482 and 483: Max. water level +16 m Min. water l
Page 484 and 485: 2-4 m marine clay dredged out MHW R
Page 486 and 487: Miscellaneous piling problems 471 o
Page 488 and 489: Miscellaneous piling problems 473 c
Page 490 and 491: The ground temperature around the p
Page 492 and 493: 9.40 URANOWSKI, D. D., DODDS, S., a
Page 494 and 495: The durability of piled foundations
Page 496 and 497: and European Standards as shown in
Page 500 and 501: martesia with some teredo, and at C
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The durability of piled foundations
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economics, taking into account the
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Depth of borehole 1.5 B 1 in 4 B Gr
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Ground investigations, contracts an
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(a) DCP n (blows/100 mm) 40 35 30 2
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Table 11.2 Daily pile record for dr
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Paper fixed to pile by adhesive tap
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Figure 11.10 Patented arrangement f
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following expressions: (11.1) Load
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(b) Settlement of pile head in mm S
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(a) Settlement � (mm) 0 0 4 8 Gro
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experience to give reasonably relia
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Appendix Properties of materials A.
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Subdivisions of Grades A to C chalk
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544 Name index Davis, E. H. 354 Dav
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546 Name index Schaaf, S. A. 424 Sc
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548 Subject index contiguous piles
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550 Subject index Pali Radice piles
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