Pile Design and Construction Practice, Fifth edition

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9.2 Piling for underpinning Miscellaneous piling problems 437 9.2.1 Requirements for underpinning Underpinning of existing foundations may be required for the following purposes: (1) As a remedial measure to arrest the settlement of a structure (2) As a precautionary measure carried out in advance to prevent the excessive settlement of a structure when deep excavations are to be undertaken close to its foundations, and (3) As a strengthening measure to enable existing foundations to carry increased loading, or to replace the deteriorating fabric of a foundation. An example of the use of piling as a remedial measure is shown in Figure 9.1a. The column has settled exclusively due to the consolidation of the soft clay beneath its base. Piles are installed on each side of the base and the load transferred to the pile heads by needle beams inserted below the base. A typical use of piles as a precautionary underpinning measure is shown in Figure 9.lb. A deep basement is to be constructed close to an existing building on shallow strip foundations. Underpinning of the foundation adjacent to the basement is required since yielding of the ground surface as a result of the relief of lateral pressure due to the excavations would cause excessive settlement. Rows of piles are installed close to the wall foundation inside and outside the building and the loads are transferred to them by a system of longitudinal and transverse beams. The external row of piles also serves as a support for the horizontal sheeting members used to retain the face of the excavation. Piling as a strengthening measure is shown in Figure 9.1c. Pits are excavated beneath the existing foundation and piles are jacked down to a bearing on a hard incompressible stratum. Underpinning of the foundations may be required where the existing piles have deteriorated due to attack by aggressive substances in the soil or groundwater. New piles can be installed in holes drilled through the cap or raft (Figure 9.1d). The new pile heads are bonded to the reinforcement of the existing substructure. Piling has a somewhat limited application to underpinning work. This is because it is usually necessary to excavate pits below the existing substructure to place supporting beams or pads. In a high proportion of the cases where remedial or strengthening works are required a suitable bearing stratum exists at no great depth and it is cheaper to take the pits down to this stratum and to backfill the void with mass concrete rather than to install piles in conditions with a low headroom and a restricted working area. Also a considerable force may be required to jack down an underpinning pile even though the soil is removed from the piling tube at each stage of jacking. There may be insufficient mass in the existing structure to provide the required reaction to this jacking force. It is not usually feasible to employ jacked piles beneath two-storey or three-storey buildings of load-bearing wall construction, since the usual mass concrete strip foundation and brick footing walls have insufficient bending strength to withstand the loading that results from jacking down a pile, even though a spreader beam is used between the ram of the jack and the foundation. 9.2.2 Piling methods in underpinning work Before underpinning by piling is considered, it is essential to determine the cause of structure– foundation instability and confirm the ground conditions at depth. Means of checking pile capacity and integrity once installed should be available.
(a) Concrete surround (c) Boredand-castin-situ piles Column propped at higher level Bearing plate Piled jacked down to bearing stratum Needle beams Soft clay Steel block Packing plates Column base to be underpinned Steel plates and dry packed mortar Hydraulic jack in inverted position Timbering to pit (d) Slab raft Existing piles (deteriorated) New underpinning piles Pad foundation Timber sheeting secured to the face of piles Steel H-piles Existing load-bearing wall Spreader beams Bearers Limiting line beyond which settlement of ground due to basement excavation will not cause excessive settlement of shallow foundations Holes drilled in raft Figure 9.1 Use of piles in underpinning (a) Remedial measures to support column base (b) Precautionary measures in underpinning strip foundation adjacent to deep excavation (c) Jacked piles to strengthen column base (d) Drilled piles to replace existing piles beneath raft slab. (b)
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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
Page 402 and 403: (a) (b) (c) M.S.plate cover M.S.cap
Page 404 and 405: 45˚ Structural design of piles and
Page 406 and 407: X Column Y9 Y9 Y Critical section f
Page 408 and 409: 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 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 460 and 461: Longitudinal reinforcement is provi
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 498 and 499: The durability of piled foundations
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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Pile Design and Construction Practice, Fifth edition

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