Calculation of jacking force by new ATV A-161

A- Accepted 6 November 2009 Available online 30 December 2009 Keywords: Pipe jacking Jacking force Structural analysis of pipes the calculation of steerable and non-steerable pipe jacking. The new concept of partial safety factors also with thermosetting materials like fibre reinforced plastics, and thermoplastics. It is planned that all codes of the ATV will use the same material parameters. Furthermore the standard design loads which occur by using technologies of steerable and non-steerable pipe jacking which are given in ATV A-125 (2007) are described in detail. certain boundary conditions the proof of dynamic fatigue for steel pipes can be omitted. The aim of this paper is to show the calculation of the forces in the longitudinal direction (allowable jacking force) for compres- sion closure pipe connections according to the new ATV A-161 (2008). The structural analysis in axial direction is not performed in this article. The determining factor for the allowable axial compressive force are the pipe cross-sections at their weakest location, the* Corresponding author. Tel.: +49 9116554852; fax: +49 9116554851. Tunnelling and Underground Space Technology 25 (2010) 731–735 Contents lists availab ro w.e E-mail address: [email protected] (R. Röhner). The ATV A-161, which was introduced first in 1990, standard- izes the structural analysis of pipe jacking. The development of new production techniques in pipe jacking were the inducement for the improvements of the ATV A-161 (2008). In parallel a new version of the ATV A-125 (2007) came out including the calculation for steerable and non-steerable pipe jacking. The new concept of partial safety factors was also a reason for the revision of the ATV A-161 (2008). One of the modifications and additional topics in the new ATV A-161 (2008) are new materials. The new ATV A-161 (2008) deals are taken into account by the parameters of soil mechanics K (earth pressure coefficient), d (wall friction angle) and c (cohesion). The new ATV A-161 (2008) gives limiting values for the ratio of wall thickness to radius and includes the calculation of curves and angular deviation due to open loop control, planned angular devi- ation and angular deviation from production tolerances. The pres- sure transmitting elements are taken into account. In addition the proofs of stability in axial and longitudinal direc- tion are simplified. For anisotropic materials the effective stresses are verified. The design tables for steel pipes are dropped and for 1. Preface 0886-7798/$ - see front matter � 2009 Elsevier Ltd. A doi:10.1016/j.tust.2009.11.005 was also a reason for the revision of the ATV A-161 (2008). One of the modifications and additional topics in the new ATV A-161 (2008) are new materials. The new ATV A-161 (2008) deals also with thermosetting materials like fibre reinforced plastics, and thermo- plastics. It is planned that all codes of the ATV will use the same material parameters. Furthermore the standard design loads which occur by using technologies of steerable and non-steer- able pipe jacking which are given in ATV A-125 (2007) are described in detail. The theory of silo (diminishment of vertical earth pressure because of arching effects) is used and soil density and consistency are taken into account by the parameters of soil mechanics K (earth pressure coefficient), d (wall friction angle) and c (cohesion). The new ATV A-161 (2008) gives limiting values for the ratio of wall thickness to radius and includes the calculation of curves and angular deviation due to open loop control, planned bending and angular deviation from production tolerances. The pressure transmitting elements are taken into account. In addition the proofs of stability in axial and longitudinal direction are simplified. For anisotropic materials the effective stresses are verified. The design tables for steel pipes are dropped and for certain boundary conditions the proof of dynamic fatigue for steel pipes can be omitted. The term of this paper is to show the calculation of the forces in longitudinal direction (allowable jack- ing force) for compression closure pipe connections from new ATV A-161. The structural analysis in axial direction is not performed in this article. � 2009 Elsevier Ltd. All rights reserved. The theory of silo (diminishment of vertical earth pressure be- cause of arching effects) is used and soil density and consistency Received 15 July 2009 Received in revised form 1 October 2009 The development of new production techniques in pipe jacking were the inducement for the improve- ments of the ATV A-161 (2008). In parallel a new version of the ATV A-125 (2007) came out including Trenchless Technology Research Calculation of jacking force by new ATV Rita Röhner *, Albert Hoch TÜV Rheinland LGA Bautechnik GmbH, Tillystraße 2, 90431 Nuremberg, Germany a r t i c l e i n f o Article history: a b s t r a c t Tunnelling and Underg journal homepage: ww ll rights reserved. 161 le at ScienceDirect und Space Technology lsev ier .com/ locate/ tust strength of the pipe material, the degree of angular deviation and the material parameters of the pressure transmission ring. For the calculation of the axial compressive force it is important to dis- tinguish between compression closure pipe connections and pres- sure/tension closure pipe connections. 2. Pressure transmission The maximum pressure in the pipe gap is governed by the total angular deviation uges of the pipes. Angular deviation is unavoid- able and appears during pipe jacking due to open loop control, curves and production tolerances of the pipes in the end planes. Angular deviation in one pipe gap is the sum of the single angu- lar deviations: uges ¼ uR þ w � ðuSt þuDa;calÞ ð1Þ w is a combination coefficient which takes into account the possibil- ity that uSt and uDa;cal occur at the same location and superpose with uR. Without detailed proof w ¼ 0:8 should be used. The single angular deviations have to be calculated as follows: uDa;cal is the angular deviation due to production tolerances at the end planes of the pipes uDa;cal ¼ arctanðDacal=da;minÞ ð5Þ with Dacal as the maximum deviation of the end planes from per- pendicularity to the longitudinal pipe axis. The values are shown in Table 1. For the strength of the pipe the pipe cross-section with the smallest wall thickness is critical. For pipes with pressure trans- mission rings, the cross-section which transmits the pressure is smaller than the regular pipe cross-section. That means that the compressive stresses in the contact area with the transmission ring are higher than in the middle of the pipe. Therefore the highest allowable stress rcal in the pipe joint must be calculated, so that the material behaviour of the transmission ring and the ratio of the gap separation zk/da,min (Fig. 4) can be determined by rcal ¼ aD � jt � fd ð6Þ with the reduction factor aD for compressive strength fd of the pipe material when only part of the cross-section is loaded 732 R. Röhner, A. Hoch / Tunnelling and Underground Space Technology 25 (2010) 731–735 uR is the angular deviation due to planned curves of the pipe line. uR ¼ arctanðLR=RplanÞ ð2Þ with LR as length of one single pipe and Rplan as the planned radius of the pipe line. If uR < 0:05�, the pipe line is assumed as being straight and uR ¼ 0� has to be taken. uSt is the angular deviation due to unscheduled deviations of the boring machine by open loop control. For a pipe line without a clothoid it is uSt ¼ uSt;0 LR � LR þ 0:0625� ð3Þ and with clothoid it must be uSt ¼ ð1� 100=RplanÞ � uSt;0 LR � LR þ 0:0625� P 0 ð4Þ with uSt;0LR from Fig. 1. For pilot headed drilling for all pipe diameters uSt;0 LR ¼ 0:05 can be assumed. Eqs. (3) and (4) and Fig. 1 are based on experience. Fig. 1. Ratio uSt;0=LR dependen aD ¼ ftmfk � 1 jR 6 1 ð7Þ jR is the coefficient from Fig. 2 (maximum value is to be used) which take into account spalling and splitting of the material. If no pressure transmission rings are used, aD = 1. fk is the character- istic compressive strength of pipe material. ftm is the tensile strength in radial direction of pipe material. Furthermore jt ¼ tpipe=tptr ð8Þ with tpipe ¼ 0:5 � ðda;min � di;maxÞ, minimum wall thickness of pipe; da,min, smallest outer diameter of pipe; di,max, largest inner diameter of pipe; tptr ¼ 0:5 � ðda;ptr � di;ptrÞ, width of pressure transmission ring; da,ptr, outer diameter of pressure transmission ring; di,ptr, inner diameter of pressure transmission ring; and with the design com- pressive strength in longitudinal pipe direction. fd ¼ fkcM;ax ð9Þ with cM;ax as partial safety factor dependent on the material. t on inner pipe diameter. Table 1 Ultimate factor Dacal considering production tolerances in (mm). Diameter (mm) Concrete, reinforced concrete, fibre reinforced concrete Vitrified clay Steel Ductile cast iron GRP (UP-GF) Polymer concrete PE, PP, PVC-U 6200 4 1 1 1 1 1 1 >200 6 300 4 1 1.6 1 1 1 1 >300 6 1000 6 – 1.6 2 1 1 2 >1000 6 2800 8 – 1.6 3 1 1.5 – >2800 10 – – – – – – Fig. 2. Coefficient jR taking into account spalling and splitting of the pipe. Fig. 3. Deformation factor ab dependent on the ratio of pipe length to outer pipe diameter. R. Röhner, A. Hoch / Tunnelling and Underground Space Technology 25 (2010) 731–735 733 ain diagram of a standardized test. ground Space Technology 25 (2010) 731–735 The loading of the pipe is determined by the jacking force and the ratio of gap separation zk da;min ¼ Dsptr þ Dspipe tanðugesÞ � da;ptr ð10Þ The deformation of the pressure transmission ring is Dsptr ¼ sd � ffiffiffiffiffiffiffiffi rcal Ecal r � da;min da;ptr ð11Þ with sd being thickness of pressure transmission ring and the defor- mation of the pipe is: LR Fig. 4. Example of the stress–str 734 R. Röhner, A. Hoch / Tunnelling and Under Dspipe ¼ rmax � jab � ER;ax ð12Þ with rmax as allowed compressive stress in the pipe rmax ¼ rcal � tptrtpipe ð13Þ ER,ax is the uniaxial modulus of elasticity of the pipe and Ecal the stiffness of the pressure transmission ring which includes the non-linear behaviour of wood depending on load history. jab is a coefficient for the non-uniform stress and strain distribution over the pipe length jab ¼ ab � ðab � 0:5Þ � ð1� auÞ ð14Þ with au ¼ uR � 0:05 6 1 ðuR in �Þ ð15Þ and au ¼ 0 for uR 6 0:05�. ab can be taken from Fig. 3. 3. Material behaviour of pressure transmission ring The stiffness of wood is dependent on the loading history. So the stiffness is determined by Ecal ¼ rcalðemaxðrcalÞ � eplðrIÞÞ2 ð16Þ with emaxðrcalÞ, maximum compressive strain of pressure transmis- sion ring due to rcal; eplðrIÞ, plastic strain of transmission ring after multiple loading with rI; and rI ¼ rcal=cf , prestress. Fig. 5. Dependence of stress ratio rmax/r0 on the ratio of gap separation zk/da,min. Fig. 4 shows an example of the stress–strain diagram of a stan- dardized test. Eq. (16) describes the non-linear behaviour of wood materials which is dependent on the prestress (loading history) and the thickness of the pressure transmission ring. 4. Jacking force The jacking force is calculated by the following equation: cF � Fj 6 A � rmax rmax r0 ð17Þ with Fj, allowed maximum jacking force; cF , safety factor for load- ing; A ¼ d 2 a;min�d2i;maxð Þ�p 4 , smallest pressure transfer area of pipe; and rmax r0 , ratio of allowable extreme fibre stress from eccentric loading rmax to stress from coaxial loading r0. Fig. 5 shows the dependence of stress ratio on the ratio of gap separation zk/da,min. 5. Calculation examples board (OSB). The ring thickness is 20 mm. The radius of the pipe line R is varied between 250 m and 500 m and the production tol- erances acal are varied with 3 mm and 6 mm. Table 2 shows the results. It can be seen that the allowable jacking force decreases with the radius R and the stiffness Ecal of the pressure transmission rings. High production tolerances in the pipe end surfaces decrease the allowable jacking force. 6. Summary This article explains the improvements of the ATV DWA A-161 related to the calculation of the allowable jacking force for driven pipes. A parameter study shows the influence of the parameters production tolerances, pipe line radius and material of the pressure transmission rings. References ATV DWA A-161, November 2008. Statische Berechnung von Vortriebsrohren, Table 2 Results of parameter study. R (m) acal (mm) Pressure transmission ring, OSB Pressure transmission ring, soft wood zk/da,min (–) Fj (kN) zk/da,min (–) Fj (kN) 250 3 0.32 1690 0.17 850 500 0.44 2217 0.24 1268 250 6 0.29 1542 0.16 750 500 0.40 2061 0.21 1090 R. Röhner, A. Hoch / Tunnelling and Underground Space Technology 25 (2010) 731–735 735 For the parameter study, concrete pipes of 1500 mm diameter and 2.5 m length are chosen. The material of the pressure trans- mission rings is varied between soft wood and oriented strand unpublished. ATV DWA A-125, 2007. Rohrvortrieb und verwandte Verfahren, unpublished. Calculation of jacking force by new ATV A-161 Preface Pressure transmission Material behaviour of pressure transmission ring Jacking force Calculation examples Summary References