INTERNATIONAL SOCIETY FOR MECHANICS AND

This paper was downloaded from the Online Library of the International Society for and Geotechnical Engineering (ISSMGE). The library is available here: https://www.issmge.org/publications/online-library

This is an open-access database that archives thousands of papers published under the Auspices of the ISSMGE and maintained by the Innovation and Development Committee of ISSMGE. Reliability of dynamic on steel pipe piles in soft rock Fiabilité des tests de charges dynamiques de pieux cylindriques dans la roche tendre

T. Matsumoto - Department of , Kanazawa University, Japan Y. Michi - Yoshimitsu Corporation, Japan M. Hayashi - NKK Corporation, Applied Technology Research Center, Japan

ABSTRACT: Dynamic load tests were conducted on a total of 32 open-ended steel pipe piles for foundations of a highway bridge constructed in soft rock called diatomaceous mudstone distributing on Noto Peninsula, Japan. Wave matching analyses of re-driving tests are performed to estimate load-displacement relation as as ultimate of each pile, based on the one-dimensional wave propagation theory. Rational soil models proposed by Randolph & Simons(1986) and by Deeks(1992) are used for shaft resistance and toe resistance respectively in the wave matching. Since the soil parameters such as spring constant, radiation damping and lumped soil mass are determined from the soil tests, only maximum shaft and maximum base resistance are identified through the wave matching. Variance of the ultimate capacity derived from the wave matching is compared with the variance of the undrained of the ground, and the reliability of the dynamic load testing is discussed.

RÉSUMÉ: Des tests de poids dynamiques ont été faits sur 32 pieux cylindriques en acier à deux ouvertures utilisées comme fondations d'un pont d'autoroute construit dans la roche tendre dite terre à diaomées, qui est répandue sur la péninsule de Noto au Japon. Des analyses de propagation d'ondes de tests de refrappement sont faites pour estimer la relation de déplacement de poids, ainsi que la capacité de support ultime de chaque pieux Cette estimation est basée sur la théorie de propagation d'ondes à une dimension. Des modèles de sol rationnels proposés par Randoolph el Simons ( 1986) et par Deeks (1992) sont utilisés pour la resistance de frottement el la résistance du bout, respectivement, dans l'analyse de la propagation, d'ondes. Puisque les données du sol telles que la constante de ressort, le taux de radiation et la masse du sol ont été déterminées à partir des tests de sol, seulement la résistance de frottement maximum et la résistance du bout ultime sont idemifées par l'analyse de la propagation d'ond. La variance de la capacité ultime provenant de l'analyse de la propagation dónde est comparée la variance de compression sans étreinte latérale, et la fiabilité des tests de poids dynamiques est discutée

1 INTRODUCTION employed in the analyses of wave propagation and static loading. The internal soil (soil plug) is modeled as a series of springs and The dynamic load testing has been widely used during the last 20 masses connected to the pile. The one-dimensional wave years. However, the reliability of the dynamic load testing to propagation through the internal soil is calculated by means of estimate load-displacement curve as well as ultimate capacity does Smith method (Smith 1960), while the wave propagation in the pile not seem to be fully investigated. This is due to that the ultimate is calculated based on characteristic solutions of the wave equation. capacity of piles driven in clayey tends to increase with The pile/soil system has been advocated by Randolph & Simons elapsed time after pile driving and that execution of re-driving is (1986). difficult in usual pile driving works. Moreover, the soil model The spring value of the internal soil is estimated from the one­ proposed by Smith(1960) that has been used often in wave dimensional modulus, E0, since radial strain of the internal soil may propagation analyses of pile driving seems to be too empirical. be negligible: Comparative tests of static load tests and dynamic load tests on open-ended steel pipe piles driven in diatomaceous mudstone on 2(1-v)G _2(i_v)G/(l-2v) (1) Noto Peninsula of Japan was carried out in 1991. The load- 1 - 2v displacement curve derived from the wave matching analysis of the re-driving test was comparable with that obtained from the static where G and v are shear modulus and Poisson's ratio of the soil. load test Rational soil models were used in the wave matching analysis Based on this result, dynamic load tests were conducted Pile pile External in 1995 on a total of 32 open-ended steel pipe piles for foundations of a highway bridge, called Noestsu Bridge No.3, constructed on the mudstone. In what follows, the procedure of the dynamic load testing used will be described first. Then, the results of the test piling and the dynamic load tests of the actual piles will be presented. Further, the reliability of the dynamic load tests will be discussed, comparing the dynamic load test results with the soil strength parameter of the ground.

2 PROCEDURE OF DYNAMIC LOAD TESTING

2 1 Pile soil system

In order to take account of the influence of the internal soil inside open-ended pipe pile, the pile/soil system shown in Figure 1 was

1185 Pile base node (or base of soil plug) 2.2 Soil resistance models Rational soil resistance models proposed by Randolph & Simons (1986) and by Deeks(1992) were used for the shaft and the base resistance, respectively, instead of the conventional Smith model. The pile displacement and the displacement of the soil adjacent to the pile are calculated separately so that the viscous damping and the radiation damping are allowed for individually (Figure 2). Relative displacements between the pile and the soil does not occur until the motivated shear stress reaches the maximum shear stress, x„,„, that is expressed by the slider in Figure 2, which is comparable with the results of shear tests between steel and by Yoshimi & Kishida (1981) According to Novak et al. (1978), the spring constant, k„ and the radiation damping, cr, of the outer shaft resistance are estimated as follows:

kx =2.75G / (ju/0 ), d0 = outer pile diameter (2) 3 CONSTRUCTION OF PILES OF NOETSU BRIDGE NO. 3 c_ = G / Vr, Vs = shear wave velocity o f soil (3)

Although the shaft model shown in Figure 2 was used also for 3 1 Ground condition and pile specifications the internal shaft resistance, the radiation damping was set to be The bearing stratum of the foundation piles of Noetsu bridge No.3 zero since the inward radiation does not occur in the internal soil. is a thick deposit o f the diatomaceous mudstone (Figure 4) The For the base model (Figure 3), the spring constant, kb, the blow count, N , from the Standard Penetration Tests (SPTs) are damping constant, cb, and the lumped mass, M b, for the annular pile shown in Figure 5. The shear wave velocity, F„ were measured base and the base of the soil plug are given as follows (Deeks at the locations of Pier Pi and Abutment A2 by means of seismic 1992): cone penetration tests. The Vs in the mudstone ranges from 250 for soil plug base; to 300 m/s as indicated in Figure 5. A total of 32 open-ended steel pipe piles were driven at k iG (4) Abutment Ai (12 piles) and Pier Pi (20 piles), with a diesel hammer h ji(1 - v ) d i having a rated driving energy of 108 kN-m, in March of 1995 The design ultimate capacity of the piles are listed in Table 1 The 3 2pFç 32G cb (5) mechanical and geometrical properties of the piles are listed in n ( l - v ) ji ( 1 - v )F 5 Table 2. Strain and acceleration, which are converted to force and -w2 0.1-v 4 M h = 2 d f p —------(6) velocity, were measured near the pile head during driving. Re­ driving was conducted on each pile different rest periods later. Comparative tests of static load tests and dynamic load tests of for annular pile base; steel pipe piles have been carried out in 1991 near the bridge construction site (see Figure 6) (Matsumoto et al. 1995) 8G (7) Thorough soil tests and site investigations of the mudstone were 0 * ( l - v ) ( d +di) conducted over a relatively wide area including the test site and the bridge construction site. The variations of the , >1. 3.2pVs 3.2 G cb - (8) the density, p, the unconfined compression strength, q„, and the secant modulus, £ 50, with depth are shown in Figure 7. It is seen that the mudstone ground is relatively uniform in plane and in (9) depth 1 3.2 Determination o f soil resistance parameters Here, d, is the inner pile diameter and p is the soil density. The new soil models were incorporated in a computer program The shear modulus, G, of the mudstone was estimated from the KWAVE which has been developed by the first author. shear wave velocity, Vs, from the relation of G=pV,2- The variations of V, with depth at Abutment Ai and Pier Pi were modeled as shown in Figure 5 from the measured Vs. 1 Pile node 20

slider Tm - 1 10 - 0 B '■'Ji— I* j1 t-.--. ht i l — -■■■ if D iatom aceous mudstone -10 Soil adjacent to pile S a n d ro c k ...... ------— ^ ------1------1------1 Jo 4 0 0 5 0 0 Distance from station point (m) dashpot c, Figure 4. Soil profile along the axis of Noetsu bridge No.3. spring ks (radiation)

i-H aiiu 1 iu 1 | . Abutment Ai Pier Pi Capacity for usual loading (MN) 3.18 2.59 Soil far from pile (fixed) Capacity for loading (MN) 3.73* 3.32* Figure 2 . Shaft model (after Randolph & Simons 1986). * required ultimate capacity 1186 A/-value A/-value /V-value A/-value A/-value A/-value A/-value o 10 20 30 40 50 0 10 20 30 40 50 0 10 20 30 40 50 0 10 20 30 40 50 0 10 20 30 40 50 0 10 20 30 40 50 0 10 20 30 40 50 Vh.

i \. Pile / : y

>\ P ie r P P ie r P - ^ P ie r P -2 T e s t s i t e ____i___ 100 200 300 400 0 100 200 300 400 V (m /s ) V ( m / s ) V ( m / s ) W - v a lu e V (Measured) ■ V (Modeled) vs (m/8) Figure 5. SPT A^-value and shear wave velocity measured by seismic cone at the construction site of Noetsu Bridge No.3 and the test site.

Table 2. Mechanical and geometrical properties of open-ended steel where

Property Value Keq=Ks +Kf /n (11) Abutment A, Pier Pt Test pile K« -Kw Number 20 12 i (12) Length (m) 9.0 (5.0+4.0) 10.0 11.0 (1 -S)-Kw +■ S ■ Ka Embedded length (m) 8.0 9.0 8.3 Wall thickness (mm) 12/9 9 12 where Ks, K¡, Kw and Ka are the bulk modulus of the soil skeleton, Outer diameter (mm) 600 600 800 the pore fluid, the saturated water(A^„ = 2000MN/m2) and the air Inner diameter (mm) 576/582 582 776 (K„ = 2000kN/m2) respectively, and n is the (n = 0.75 for Cross-sectional area (m2) 0.022/0.017 0.017 0.041* the mudstone). Young's modulus (MN/m2) 2.06 x 10s 2.06 x 105 2.06 x 10s The soil parameters except for the maximum shear stress, xm„, 5120 5120 5120 Wave velocity (m/s) and the maximum base resistance, <74, were determined by means of * including the cross-sectional areas of steel channels for protection of Equations (2) through (9) with v = \ eq. Only xmiu and qb were strain ga g es. identified from the wave matching. The static load-displacement curve was calculated with the identified xma( and <74, and the drained Noetsu Bridge No. 3 value of the base spring, kb. Moreover, the shaft spring, k,, under A, P, P2 P3 Pi 450m static loading was estimated according to the following equations (Randolph 1991): Test site in 1991 Constructed in 1995 ^ m ^s(stal) I ^s{dyn) = 2jl/(2.75^) ( 1 3 )

Figure 6. Locations of Noetsu bridge No.3 and the test site. 5 = ln[5.0(l-v)/^/^0] (14) where Id is the embedded pile length. w (%) p (ton/m3) <7 „ E50(MPa) 40 80 120 160 0.0 0.4 0.8 1.2 1.6 400 800 1200 0 40 80 120 160 20 "r- ,- T ~ Co (5 o o o o 3.3 Comparison of dynamic and static load tests on test pile Ê 10

<£> ^ O o 0 o

N . Validity of the wave matching procedure mentioned above was

- 1 £. o c 0 0 examined against the static load test of the test pile. The test pile o -to £ 0 _ >a - 0 0bfc>- uo ° eft* œ - specifications has been listed in Table 1. The re-driving of the pile 0 . 0 0 o was conducted 66 hours after the end of initial driving (EOID). UJ .20 o o _

1187 Load on pile head, P (MN) i Load on pile head, P (MN) 1 2 3 4 ------C alculated 1 2 3 4 3 ...... M easured • Z 2 2 ''/N 0) \ \ o \\ o 1 Q- . 20 ------End of initial driving V V* ------Re-driving 0 J (66 hours after EOID) V ...... SLT \ - End of initial driving (29 days after EOID) 0 10 15 20 25 30 3 _ - Re-driving Û. 35 Time, t (ms) Q- 35 1- Figure 8. Comparison of load-displacement Figure 9. An example of wave matching Figure 10. Load-displacements curves of all curves from dynamic load testing and static load for pile of Abutment A]. piles at Abutment A( derived from wave test. matching. “i---- •---- r~ z 5 n = 69 qr = 858 kPa - S o - 1 O o o ° 0 8 : C.O.V. = 0.15 & Design ultimate o 3 O © Design ultimate - c bearing capacity” ;° o° ro : cp ° ; bearing capacity ■ 2«/> 2 a> o 1 Abutment A - Hat EOID! Pier P - 5 - foi= 1 ?} at EOID 1 . «j 1 . & n o xu 100 101 102 103 104 105 106 100 1 01 102 1 03 1 04 1 05 106 400 600 800 1000 1200 Elapsed time after EOID, t (min) Elapsed time after EOID, t (min) Unconfinded comp, strength, q (kPa) Figure 11. Increase in static resistance of piles at Figure 12. Increase in static resistance of piles Figure 13. Frequency distribution of Abutment Aj as function of elapsed time after end at Pier P] as function of elapsed time after end of unconfined compression strength of the of initial driving. initial driving. mudstone.

Abutment A] (1) Reliability of the dynamic load testing at re-driving is n = 14 improved by the use of the rational soil models with Rs = 3,76 M N - data including physical and mechanical properties. CO V = 0.07 (2) Execution of the dynamic load testing on all piles in a construction site is possible and may assure the reliability of piled foundations as well as individual piles.

Seismic data were obtained by Mr. H H i In Sasao and Mr. K Takesue of Kajima Technical Research Institute 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 Static resistance, R (WIN) Static resistance, R (MN) Figure 14. Frequency distribution of static resistance of piles at REFERENCES Abutment Ai and Pier Pi. Deeks, A.J. 1992. Numerical analysis of pile driving dynamics PhD Thesis, The University of Western Australia. The increase in the static resistance (set-up) of piles at Abutment Matsumoto, T., Y. Michi & T. Hirano 1995. Performance of axially A] and Pier Pi as a function of elapsed time after the end of initial loaded steel pipe piles driven in soft rock. J. Geolech. Eng.. ASCE driving are shown in Figures 11 and 12, respectively. It is seen 121 (4):305-315. that the set-up ceases at about 100 minutes in Abutment Ai and Novak, M., T. Nogami & F. Aboul-EIla 1978. Dynamic soil reactions about 30 minutes in Pier Pi. The estimated static resistance after for plane strain case. J. Mech. Eng. Div.. ASCE, 104(EM4): 953-959 these time instants exceeds the required ultimate capacity. Randolph, M.F. 1991. Analysis of the dynamic pile driving Figure 13 is the frequency distribution of qu which has been Chapter in Developments in Soil Mechanics - IV: Advanced indicated in Figure 7 The frequency distributions of the static Geotechnical Advances, P.K. Banerjee & R. Butterfield (ed.): Elsevier Applied Science. resistance, Rs, after the elapsed time of 100 minutes in Abutment Randolph. M.F. & A.J. Deeks 1992. Dynamic and static soil models Ai and 30 minutes in Pier Pi are shown in Figure 14, with the for axial pile response. Proc 4th Int. Conf. on the Appl. of Stress- statistical properties such as the average and the coefficient of Wave Theory to Piles. The Hague. 3-14. variance, COV. All the frequency distributions seem to take the Randolph, M. F. & H.A. Simons 1986. An improved soil model for form of normal distribution. The COVs of Rs at Abutment Ai and one-dimensional pile driving analysis. Proc. 3rd Int. Conf. on Num. Pier Pi are 0.07 and 0 06, respectively, that are about half of the Methods in Offshore Piling, Nantes: 1-17. COV of q„ This results seem to be reasonable, because the piles Smith, E.A.L. 1960. Pile driving analysis by the wave equation J are 'perfect' friction piles where the average of the soil strength, q„, Soil Mech. and Found., ASCE 86: 35-61. may be related to the total shaft resistance. Verruijt, A. 1969. Elastic storage of aquifers. R.J.M. DeWiest (ed). Flow through Porous Media, New York: Academic. Yoshimi, Y & T Kishida 1981. A ring torsion appratus for 4 CONCLUSIONS evaluating friction between soil and metal surfaces. Geotechnical Testing J. 4(4): 145-152. The implications from this study are as follows:

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