E3S Web of Conferences 38, 03024 (2018) https://doi.org/10.1051/e3sconf/20183803024 ICEMEE 2018 Prediction of Surface Subsidence Caused by Rectangular Pipe Jacking Construction Chao ZHANG1, Qi Jun JIA1, Ri Qing XU2, Su Yang FENG2* 1China Road and Bridge Corporation, Dongcheng, Beijing 100011, China 2College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, Zhejiang 310058, China Abstract: Based on the development of rectangular pipe jacking, the characteristics of rectangular pipe jacking are introduced. The difference between surface settlements caused by rectangular pipe jacking is calculated by stochastic medium method and peck formula method. The influence of section shape on rectangular pipe jacking is analyzed. The results show that the calculation results of the stochastic medium method are more reasonable. used for a variety of shapes of tunnels or pipe jacking. Wang [7] calculated the surface subsidence induced by 1 Introduction ground loss under rectangular pipe jacking construction. Pipe jacking is a technique used for installing pipes under However, it was assumed that the soil in the rectangular the ground using a tunnel boring machine and hydraulic pipe jacking was uniform convergence, and lacked jacks located inside a jacking pit. A shield is inserted into in-depth study. In this paper, stochastic medium method the ground through a drive shaft or reception point and is used to calculate the surface subsidence caused by cuts a bore. As the shield advances forward, excavating rectangular pipe jacking under uniform and the earth in its path, sections of pipe are jacked into place inhomogeneous convergence modes. What’s more, directly behind it using powerful hydraulic jacks. As a compared with measured values, the applicability of means of trenchless construction, the pipe jacking Peck formula in rectangular pipe jacking is discussed. technology has been fully developed in the world. It has accumulated a lot of experience in terms of the large 2 The characteristics of rectangular pipe diameter, long distance and curve jacking construction jacking [1-3]. The cross-section of the jacking is mostly circular. In This paper collects some representative pipe jacking the early 1970s, the rectangular pipe jacking technology projects around the world. As can be seen from Table 1, was used in Japan for the first time. While in 1999, the the cross-section of the rectangular pipe jacking is too first rectangular pipe jacking was completed in the large, as the equivalent radius is often greater than 1.8m underground pavement project of entrance 5# in Lujiazui and it can be regarded as large diameter pipe jacking station, line 2, Shanghai Metro, China[4]. according to the code for circular one. It also indicates Since most rectangular pipe jacking projects are that the depth is shallow because the ratio of depth to the located in the bustling area, there is a high demand for equivalent radius is usually less than 3. Besides, the surface subsidence control. The existing calculation jacking path is shorter. Rectangular pipe jacking is often methods of ground settlement include Peck formula used for subway entrances; the ground outside is mostly method [5] and stochastic medium method [6] [7]. Peck trunk lines and dense buildings, so a stricter ground formula method can be applied to circular tunnel and subsidence control standard is required. jacking, but the rectangular pipe jacking remains to be verified. Nevertheless, stochastic medium method can be Table 1 Partial geometric parameters of rectangular pipe jacking projects Buried Jacking Number of Project Width×height Depth /m Path /m Jacking Underpass tunnel in Zhongzhou /′ 8 9.0m 6.1m 1.91 110 4 Avenue, Zhengzhou, China Entrance 5# in Culture Park Station, 6.9 6m ×4.3m 2.41 52 1 × * Corresponding author: [email protected] © The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/). E3S Web of Conferences 38, 03024 (2018) https://doi.org/10.1051/e3sconf/20183803024 ICEMEE 2018 line 6, Guangzhou Metro, China Entrance 4# in Wangjiadun Station, 7.9 6m 4m 2.86 62 1 line 2, Wuhan Metro, China Entrance 3# in Pudian Road Station, 7.9 6.2m×4.4m 2.68 42 1 line 6, Shanghai Metro, China Channel from Huaqiang North Station 5.95 6.9m×4.9m 1.81 41 3 to Huaxin Station, Shenzhen, China Sewer tunnel in Kikuta-gawaroute 2, 5.0 4.4m×4.0m 2.11 2 Narashino, Chiba-ken, Japan Box-type pipe jacking pedestrian 6.65 6m×4m 2.41 45 1 tunnel in Kota, Indonesia The× calculation of the surface settlement horizontally 3 Stochastic medium theory caused by ground loss can be obtained by integrating the settlement area: The whole excavation is decomposed into infinitely 1 small excavations from a statistical point of view, sx( )= exp( − x2 ) d d 2 assuming that the soil is not condensed, the density does rz() rz () not change, and the rock mass is incompressible. The effect of the upper rock mass should be equal to the sum of the effects of infinitely small excavations. That is what we call stochastic medium theory. Under the plane strain condition, the ground traverse settlement trough caused by excavating the micro-unit at deep z is: 1 = − 2 se ( x ) exp(2 x ) dd rz() rz () rz( )= z / tan Where r(z)is the main influence radius on the horizontal plane, otherwise known as the main scope of Figure 1 The excavation of unit under the plane strain influence, β is the main influencing angle of upper tunnel condition surrounding rock. The relationship between β and the With reference to the engineering experiences of width of settlement trough i can be obtained by circular pipe jacking [8], there are two kinds of comparing Peck formula method and stochastic medium convergence modes for rectangular pipe jacking, uniform method: convergence and non-uniform convergence. In the uniform convergence mode, the pipe jack is suspended in z0 tan = the slurry jacket, and the gap between the top pipe and 2 i the soil is equal to the bottom clearance. In the The calculation method of i value in stochastic non-uniform convergence mode, by contrast, the jacking medium method includes Knothe Formula and the is sinking as a whole and the bottom clearance is zero. method proposed by Han [8]. When tunneling machine advancing, the angle (1) Knothe Formula between the advancing direction and the horizontal z i = 0 direction is greater than zero during rectangular pipe 2 tan 45− jacking. And the cross section of rectangular pipe jacking 2 is generally large; the bottom of the pipe is in direct Where is internal friction angle of soil. contact with the soil due to its own weight. Therefore (2) Han’s method non-uniform convergence mode is more in line with the φ i= Kz actual situation. 0 20 Assuming , ∆B can be inferred by the rate tan = of ground loss: 50 − 1∆ = ∆ kAB Where K is based on the experiences of different =B[()()4] − A + kB + A + kB 2 + types of soil. 41k − As Knothe Formula is mainly applied to all types of Where ε is the rate of ground loss, that is, the amount rock, while pipe jacking technology is usually used in of ground loss is divided by the actual excavation area of soft soil areas, the second method is used to calculate the the pipe jacking. influence angle β in this paper. 2 E3S Web of Conferences 38, 03024 (2018) https://doi.org/10.1051/e3sconf/20183803024 ICEMEE 2018 line 6, Guangzhou Metro, China Entrance 4# in Wangjiadun Station, 7.9 6m 4m 2.86 62 1 line 2, Wuhan Metro, China Entrance 3# in Pudian Road Station, 7.9 6.2m×4.4m 2.68 42 1 line 6, Shanghai Metro, China Channel from Huaqiang North Station 5.95 6.9m×4.9m 1.81 41 3 to Huaxin Station, Shenzhen, China Sewer tunnel in Kikuta-gawaroute 2, 5.0 4.4m×4.0m 2.11 2 Narashino, Chiba-ken, Japan Box-type pipe jacking pedestrian 6.65 6m×4m 2.41 45 1 tunnel in Kota, Indonesia Figure 2 Uniform and non-uniform convergence mode The calculation of the surface settlement horizontally × Take the vertical axis of the surface z=0, the be obtained: 3 Stochastic medium theory caused by ground loss can be obtained by integrating the calculation formula of soil settlement in two modes can (1) Uniform convergence mode settlement area: c11 d tan tan 22cdtan tan The whole excavation is decomposed into infinitely 1 sx( )= exp[ −−− (x )22 ]d d exp[ −− (x ) ]d d small excavations from a statistical point of view, sx( )= exp( − x2 ) d d 22 rz() rz ()2 b11 a ba assuming that the soil is not condensed, the density does (2) Non-uniform convergence mode not change, and the rock mass is incompressible. The cd11tan tan 22c2 dtan tan sx( )= exp[ −−− (x )22 ]d d exp[ −− (x ) ]d d effect of the upper rock mass should be equal to the sum 22 of the effects of infinitely small excavations. That is what ba11 b1 a non-uniform convergence we call stochastic medium theory. Under the plane strain As shown in the figure, there is a big difference condition, the ground traverse settlement trough caused 4 Comparison of stochastic medium between the uniform convergence mode and the by excavating the micro-unit at deep z is: method and Peck formula method non-uniform convergence mode. The maximum 1 = − 2 se ( x ) exp(2 x ) dd settlement value of the uniform convergence mode is rz() rz () In order to estimate the settlement, Peck put forward the always smaller than that of the non-uniform convergence rz( )= z / tan empirical formula for the shield tunnel or circular pipe mode.