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Large diameter pipe Trenchless Technology

Categories:Shaft Construction
Time of issue:2022-06-15

(Summary description)In recent years , Tianjin urban infrastructure big leap in the speed of development, gradually expand the scale of the city , sewage emissions increase , coupled with the protection of water resources , rain sewers diversion , urban flood control capacity, the New Castle underground drainage network construction scale , greatly increasing every year . With the city traffic volume increased year by year , to increase the length and width of road , the road under the rain water pipe length is increasing in diameter increases to meet urban needs.

Large diameter pipe Trenchless Technology

Categories:Shaft Construction
Time of issue:2022-06-15 16:16
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Information

In recent years , Tianjin urban infrastructure big leap in the speed of development, gradually expand the scale of the city , sewage emissions increase , coupled with the protection of water resources , rain sewers diversion , urban flood control capacity, the New Castle underground drainage network construction scale , greatly increasing every year . With the city traffic volume increased year by year , to increase the length and width of road , the road under the rain water pipe length is increasing in diameter increases to meet urban needs.

1 Project Overview

1.1 Overview ; geology , surveying the lot construction pipeline geological conditions in which soil

Design of piping in the road surface , the depth of about 7m of silty clay , silt , silt -like silt , (4.9m following is brownish gray plus a small amount of shells ) . Groundwater situation ; geographical high water table , visible under the surface of groundwater depth of about 1m .

1.3 geomorphology and engineering characteristics

1.3.1 Taku key roads belonging to the city , regardless of how the construction process should be able to guarantee current road crossings , pipe jacking construction process must reach the top wells requires otherwise, the road does not allow open pit .

1.3.2 The site is located in the downtown area , all kinds of roads and the surrounding ground and underground pipelines, facilities , obstacles more, for the protection of various types of pipes underground cable security , it needs to be taken to reinforce and necessary cut change , etc., to the increased construction difficulty .

1.3.3 site a large scale, but the narrow construction site . Also requires the construction unit to reduce the disturbance , reducing the surrounding area , many on both sides of the pipeline design enterprises, residential building, close to the pipeline because of the distance , the construction of residential buildings in order to protect the safety , how to construction , the need to provide reliable technology solutions and necessary measure.

1.3.4 Construction of pipelines and bridges construction at the same time , how to coordinate operations in the interludes , well-organized interchange construction , and focus on civil construction and environmental protection , to ensure the project is on schedule to complete the focus .

(2) Construction

2.1 Construction preparation

2.1.1 The construction process selection ; considering Taku many kinds of anterograde pipelines , sewage interceptor design all pipe diameters d2600mm All pipe jacking . Pipe jacking can meet the engineering requirements ? The key is to have reliable technology solutions to the different soil , pipe jacking conditions , selection of top tube adapted form . Under the existing pipe jacking technology company with three kinds of artificial tunneling type ﹑ EPB , Slurry balanced pipe jacking , each has its advantages . The project pipeline overburden depth , groundwater volume of the activities , the use of artificial excavation Pipe Jacking first to reduce the water due to mandatory precipitation will lead to the road foundation settlement, resulting in the destruction of the building , causing a series of problems and therefore should not be used for driving and style top tube . And the pipelines to be applied after the completion of road construction , in order to reduce the area and ensure the broken road pavement settlement does not occur , all piping used in all EPB machine head into the construction .

2.1.2 determine the process ; diameter pipe jacking up d2600mm city is currently the largest diameter pipe jacking . South China Construction precedent for many cutter models, the construction method ensures that the settlement does not occur in and around the road safety of the buildings .

The construction d2600mm drains , pipe outer diameter Ф3120mm, if the choice of multi- cutter method of construction equipment , the nose structure is relatively simple, economical , less equipment investment per pound . Multi- cutter model of the form , in the inner circle of the head interface , divided into four areas, each area has a small diameter at the cutting cutter . Independently rotated by the motor-driven , cutting the soil ; four-blade cutting disc all the end surface area of about 50% , and the rest into the screw excavated by extrusion machine . The machine head weight, relative to the stream for geological Moon and other soft soil .

Taku subsurface soil variability, soil geological data show large values of N , hard soil . Ground surrounding buildings, underground structures , laying things more . According to experience , pipe jacking machine selection should be selected cutterhead , a large section of mining soil . Technology is feasible . Because cutterhead cutting soil area of 100 % models fit a wide range of soil . We have used the specifications d2200mm models, experience shows ; cutterhead most suitable for the city of clay , silt , sand soil characteristics .

2.1.3 Mechanical excavation performance ; This d2600mm EPB TBM top tube , the choice cutterhead models used to cut , pre-construction , according to the city's geological data , etc., to determine d2600mm TBM cutterhead pipe jacking equipment torque . As the pipe diameter increases , the increase in cross-section for the cutter , cutter cut in the clay soil resistance torque to be calculated. To provide data processing factory . How much torque should be selected leaving cutter cutting force fit ? In a preferred design for the selected cutter speed 2.0rpm conditions, according to the formula : T = ∫ 10khrdr calculation cutter cutting force :

T - cutterhead torque kN · m;

k - knives in the cutting process unit area by cutting resistance 1kg/cm2;

h - cutting tool during each revolution of soil thickness 0.3m;

r - radius cutter cutting 1.56m;

By calculating d2600mm cutterhead torque 365.8kN · m equivalent (36.58t · m)

Torque to meet the above cutter , the electric power to be input by the following formula:

N = { constant 1.026 × ( T × knife cutterhead torque rotation speed r)} / efficiency η = kw

N - Enter the top tube with a knife disc torque power (kw)

r - Cutter speed 2.0r/minη-- mechanical efficiency 0.85

Calculated d2600mm required input power : 1.026 × 36.58 × 2.0/0.85 = 88.308kw

TBM cutterhead mechanical appearance models

Sewage interceptor design diameter d2600mm, construction of pipelines EPB TBM top tube , according to the status quo option cutterhead different soil models , flexible operation , advanced technology and dump smooth, safe, reliable , using the dry dump , waste dirt minimal impact on the environment and pollution , soil Sinotrans deal simpler.

2.2 Construction Design

2.2.1 pit and receiving pit design work

Construction is based on design drawings as the basis to determine the location of inspection wells and wells used to check the settings for the jacking pit and receiving pit work . 1 # -10 # 1300m pipeline construction segment , invested a total of three sets of pipe jacking jacking underground construction equipment , the main work jacking pit pit the top two-way , east to west each jacking length 142m.

Surveying the pile after dug trenches, working pit into steel piles , 1 # -10 # for construction Crawler vibrating pile driver hit the pit mouth along the line to fight steel piles , 16t crane with the construction . Piling should be to ensure the verticality of steel piles using vibratory hammer slowly all steel piles driven into the ground will require elevation, working pit steel piles into the back spacing 0.3m, the remaining 0.8m, pile length 15m, dragon gates on both sides 0.2m away from each tube jacket playing a steel piles . With two 15 × 15cm square timber made horizontal control beam, angle steel with 10 × 10cm vertical control planes,

2.2.2 The play set cement mixing pile

Work Kengbian play set cement mixing pile, not to protect the working pit collapse , non-porous , waterproof curtain designed for pit . First place in the pit outside line, dug trenches pile rig into place, play set cement mixing pile curtain , curtain pile diameter 0.7m, bite 0.20m, pile length 14m cement parametric 15%. Important parts such as the back cement parametric 20%. . Cement mixing pile grouting using metering pumps to ensure linear meters of cement. Stir into the pile method of operation , occlusal must complete continuity of the project , the amount of external control spraying powder doped with 3% gypsum slurry to increase the condensation rate, in order to ensure the strength of cement , control water-cement ratio . The use of biaxial rack piling machine to ensure mixing pile and pile verticality lap .

2.2.3 determine the control soil pressure and thrust force

( A ) the system should be based on the construction of earth pressure to determine the soil conditions calculated as follows:

The ground soil bulk density γt = 19.3KN / m³ soil cohesion C = 14kpa soil internal friction angle Ø = 24 ° tube center depth h = 6.5m.

Control soil pressure determined ; earth pressure at rest and experience factor product , using the formula P = P0K0 calculated control

Ρ0- rest earth pressure (kpa), which is the control center of soil bulk density γt and the depth h of the product.

K0- rest earth pressure coefficient , experience value 0.75 ( the value in sandy soils K0 = 0.4-0.9 range of variation ) was calculated control soil pressure P control = 90kpa.

Since the actual process , set the control earth pressure can not be a constant value , plus the value of the pressure variation ΔP , by experience in the range of changes 20kpa , P control - take 110kpa

( 2 ) Calculation of jacking force :

Earth pressure balance pipe jacking , the total force F total designed primarily by top pipe-jacking in the face of resistance F0 and head tube length integrated propulsion resistance F , namely F total = F0 + F. Diameter ф2600mm normal face resistance when jacking F0 approximately 70t, the initial thrust that face resistance , which consists of boring machine in front of earth pressure, ground water pressure , and additional resistance component , top edge by the empirical formula F = KfπDL calculations,

F- jacking force (t)

K- safety factor ( take 1.2 )

D- Tube OD 3.12 (m)

L- jacking Length 140 (m)

f- slip coefficient of friction ( friction coefficient in sandy soils is 0.6 ) .

140 m distance from the top into the design of the top force F total = 1058t.

2.3 Construction equipment installation

2.3.1 The main roof installation

Work on the top of each pit features six main hydraulic jacks (320t),, jack stands of three layers placed jack . On the ground equipped with hydraulic stations, two high-pressure pumps, flow 2 × 25L/min, pressure 31.5Mpa high pressure pump is connected with high pressure tubing connected to the jack . Lifting with a crane mounted jack stands , steady loading jack, jack with a flat pad on the position to make small adjustments to adjust the jack stable level , and to six points fall together jack tube diameter at the center .

2.3.2 stable iron mounting rails and back

Rails using homemade heavy composite rails, and base embedded steel welded rail spacing shall be arranged so that the tube from the outer end of the horizontal channel top surface is not less than 5cm, the laying of rails to control the elevation and midline errors. Back iron composite shape back iron, the back of the plane perpendicular to the rails , back iron and concrete pit wall between perfusion (C20, thickness 10 ~ 15cm) vertical leveling.

2.4 in Construction

2.4.1 The initial top ; nose into the hole before the mouth of the pit in front of the work to be uprooted steel piles , clear open after mixing pile ho, head on the rail onto the top hole into the soil , to the front nose and close the top soil cave strict, so Dokura gauge value of setting , after a certain time pressure drops to a certain value , the resulting value is the actual static earth pressure , used as a control earth pressure reference. Also, to prevent blade machine plunged head down , in the first one between the tube and the nose , plus four M36 bolts , was well -shaped layout with embedded iron welding .

At the beginning of the top front must be a good first tube measuring elevation and midline shift , a good grasp of equipment installation, such as jacks are not synchronized, or jack larger difference between the top edge , or install a lack of precision , top edge into force line bias, influence the quality of the entire pipe jacking . Each section of pipe jacking shall be Shanghao apron, help spread Vaseline on the apron . Then the next O -shaped top rail , tube and open -ho will stabilize the anterior segment tube top tight

Buried in the standard state control , so that the whole pipe jacking have a good start, just head into the top soil pipe used when four hydraulic jacks (320t) jacking slower speed in 2cm/min.

EPB cutterhead models for the screw machine unearthed by the nose in front of cutterhead cutting in front of the slow boring of soil excavated from the soil by the screw conveyor bucket , pipe laying 15kg / m of soil bucket tube light rail shipped , transported by crane arrived to the ground loading Sinotrans .

When the nose into the top soil has been about 10m , in order to reduce the resistance of the soil on the pipeline needs to start grouting , grouting pressure is 0.3Mpa about grouting volume control on the theoretical value of 1.5 times, grouting should follow the "first after the top note , with the top with the note" of the order.

2.4.2 Measurement

Installing laser theodolite ; away from the back wall jack at 1 meter is installed between two laser theodolite, theodolite point should be at the center of the line , the installation should be installed Level bracket , bracket Φ40mm steel and 3mm thick steel plate production, in front of the instrument by the control point on the ground lead to the center of the tubing theodolite theodolite pit stand . jacking ago , according to the pipeline location and surrounding buildings settlement observation measuring step set point record the measurement results do

Measured using the J-2 guided laser theodolite, laser theodolite offers hit on the nose center receives target for head positioning . The cabin is also equipped with a tilt meter , used to monitor horizontal boring machine head longitudinal and radial deflection state , correction according to the pipe run trend correction, based on instrumentation data correction correction , during the advance correction, so jacking in order to achieve a higher quality requirements.

2.4.3 jacking operation

Pipe jacking operations personnel selected must have qualifications and experience in the jacking process will be drawn randomly jacking curve efficacy midline deviation from random measurement errors need to be adjusted according to jacking top speed , in order to facilitate corrective action.

In the jacking process, the control soil pressure values with the theoretical values close to the active earth pressure and passive earth pressure , between the practical application , we will control the pressure 100kpa soil around earth pressure should be less than head control cutter in front of passive earth pressure , and larger than the cutter in front of the active earth pressure , operation, control soil pressure changes , monitor cutter motor current. pressure exceeds the set current to earth in earth pressure , cutter motor current increases , d2600mm machine design 4 sets of fixed cutter motors , each motor rated current 90%, 22KW/37A. Current square cutting torque exceeds the design value , the electrical switch is immediately cut off the head and the main top- jin in the excavation stopped advancing , reducing the top speed , can reduce torque front , cutter load is reduced , the switch is reset. Rear hydraulic station resumed jacking .

Back top tube is displaced or uneven , makes the pipe axis deviation is too large, so that the top edge force line offset , resulting pipeline bias. Pipeline deviation is too large, so that the pipeline bends , interfaces leakage , or even cause damage to pipe section can not be restored .

Long top tube, positive resistance uneven ground , the nose discontinuity , causing the tube axis deviation . As the top tube, is a dynamic process piping , pipe jacking force the nose is conveyed through a pipe jacking force main , part of the pipeline through by soil disturbance force , so that the top tube pipe as road blocks were placed arc, also form deviation , nose correction value according to the design requirements of the axis control within 5mm , pipe jacking process in operation throughout the always correcting correction . Identify problems and take appropriate measures to ensure uninterrupted normal jacking . Close to the hole should be encrypted measurement , and to always do a good job jacking length , elevation and midline shift , time, and when the top jacking force records, 3 # -4 # pit construction, surrounded ф600mm water pressure pipes, after controlling soil pressure here can not be exceeded, otherwise it will happen so that utilities are affected, endangering the normal use and safety . Operator control soil pressure after redefining caution to make the pipe more smoothly walk through the past,

2.4.4 Grouting drag reduction :

Grouting pipe jacking is used for drag reduction , requiring the concrete pipe to form a complete slurry outer collar . Over the grouting holes arranged in the middle of the tube , the top and bottom holes not very good resistance to form a slurry of different rings, less resistance less effective now grouting holes arranged in rings within rings within the first slurry to form a complete set , grouting doubled. grouting holes with concrete pipe set in the nose , the continuous release three four sections , and then press the pulp to fill some holes spaced grouting with concrete pipe . grouting recipe: soil should be used in a different a different ratio , according to the soil conditions Dagu Road grouting drag reduction of sodium bentonite was prepared as follows :

Bentonite : Water : Alkali

22.8% : 76.2% : 1%

Drag reduction include grouting and waxing , grouting equipment should be close to the working pit , including mixed pulp , slurry storage tank, injection pump, storage tank ; grouting with a pump, its stock inlet connections for ordinary hose, the pulp port connection for high pressure hose . In the concrete wall of the grouting holes embedded 1 " threaded pipe band , which consists of plastic one-way valve sealing , grouting holes each section tube set 4 , the position along the circumferential uniform . Jacking drag reduction at the end of in proportion to the fly ash and cement mix synthetic pulp, pressed into the pipe wall would displace thixotropic slurry to prevent ground settlement after construction .

2.4.5 Construction Effects

d2600mm large diameter pipes , the day and night construction, project completed on schedule. Tests by the relevant units pipeline construction , the quality is excellent : 3 # -4 # -5 # pits, two empty pipe elevation maximum error : +2,-3cm, Right deviation are 1cm. Control deviation in the minimum range . The construction set with mud reduced friction measures to control the jacking pipe jacking force in the 140m length of the top force of 840t. Two empty pipe jacking progress were completed in 9 days 10 days . Jacking preferred process control parameters depend on the land subsidence control is better, by measuring new pavement settlement was as -15mm.

3 Construction Summary ; This construction is summarized as follows :

3.1 Mechanical greatly improve drainage pipe jacking construction efficiency , the amount of work done in the past is difficult to be completed on schedule , and to reduce the impact of construction on the surrounding environment .

3.2 Process Change " first ground, the ground after the" traditional construction process , the initial attempt to build a new road paved under the top tube carrying data and construction experience , saving construction time.

3.3 large diameter pipeline construction had preferred process and parameters , are digging in the soil after long pipe jacking , how much dug soil , the ground is not settlement, road safe , traffic continues to pass.

( In the rush manuscript allow modifications )

About the author Ding Yi Ming, male engineer, born in 1955 , the state two project managers ; , mainly engaged in construction of municipal works , pipe jacking research, metro shield construction and construction management and other work .

Author Address: East Road, Hebei District, Tianjin production head on the 3rd ( Tianjin Urban Construction Group Six has five branches ) Zip: 300250

Phone 022-26782807 E-mail dr126-05@126.com five branch chief engineer.

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Large diameter pipe Trenchless Technology

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