Study of Herrenknecht's DirectPipe Technology and Cyclone Model Simulation

Various methods for crossing works have so far been applied in order to build steel pipelines. Pipe Jacking and Segmental Lining allow for the construction of concrete protective tunnels with subsequent insertion of the product pipeline. The HDD method, indeed, allows the laying of a steel pipeline but includes the construction of a pilot bore and several hole opening steps prior to pipe pull-in. Recent developments such as the Easy Pipe method comprise jacking processes where tight connection interim steel pipes are pushed towards the target shaft, coupled to a pipeline and then can be pulled back together in a second step. All these methods include a two- or multi-step pipe installation process.

(courtesy of Herrenknecht AG., Germany)

The development of the DIRECT PIPE method, which is a combination of Micro-tunneling and HDD, was not only based on the creation of a one-step pipe laying method but also on the provision of an efficient alternative to existing methods, which is able to minimize the geological risks (e.g. drill-hole collapse using HDD). With Direct Pipe steel pipelines can now for the first time be jacked efficiently and fast in one operation process. The direct installation of the pipeline allows for continuous drill-hole support preventing borehole collapse. (Figure 1).

The Direct Pipe machine is mounted in front of the pipeline and is welded onto it (Figure 2). The Pipe Thruster, which is located in the launch pit, operates as thrust unit - clamping the pipeline on the outside and pushing the machine as well as the pipeline into the ground (Figure 3). The tunnel face is excavated by the Direct Pipe machine similar to the pipe-jacking method, which has been established for several decades. The cutting wheel can be equipped with cutting tools adapted to the specific geological conditions. In contrast to HDD technology, larger boulders, hard rock as well as soft, unstable soils (gravel) can be crossed. The excavated material is removed via a slurry circuit with separation plant in order to separate the spoil from the slurry liquid before feed pumps transport the liquid back to the tunnel face.



The Direct Pipe machine is controlled from the operating container. A gyro compass and a hydrostatic water leveling system are used for the horizontal and vertical machine surveying. To facilitate the controlled steering of the machine (and therewith the connected pipeline), the Direct Pipe machine is longer than an ordinary micro-tunneling machine (approximately 12 meters instead of 6 meters). At the end of the Direct Pipe machine a lubrication ring is mounted in the transition area between and the product pipeline, where most of the bentonite is added in the annular gap, in order to reduce the friction between the pipeline and the ground to a minimum.

Table 1. QUEUE elements in DirectPipe model

Element number	Description	Generate	Quantity	Resource Type
1	Pipes in site storage	-	12	Pipes
4	Needs connector	-	-	-
7	Crew A idle	-	6	Crew A
8	Needs check connection	-	-	-
10	Connection ready	4	1	Connection
11	Position occupied	-	-	-
12	Position available	-	1	Position
15	Pipe section ready to thruster	-	-	-
17	Pipe section ready to installation	-	-	-
19	Crew B idle	-	4	Crew B
21	Crane idle	-	3	Crane
25	Needs lubricants	-	-	-
27	Bentonite ready	-	1	Bentonite
28	Lubricants ready	4	1	Lubricants
30	Spoil tank full	-	-	-
32	Backhoe ready	-	1	Backhoe
33	Truck ready	-	1	Truck
34	Spoil tank not full	4	1	Spoil tank
35	Pipes in distance	-	-	-
37	Control room to command	-	1	Remote control room
38	Thruster ready	-	1	Thruster
40	Slurry needs recycle	-	-	-
42	Water ready	4	1	Water
43	Cable and hose ready	-	1	Cable and hose

Table 2. COMBI elements in DirectPipe model

Element number	Description
2	Bring pipes to connecting
5	Connect / weld pipes
9	Check pipes connection/welding
13	Attach pipes to crane
16	Roll pipes to thruster machine
18	Pipes setup/installation
26	Mix lubricants
31	Empty spoil tank
36	Uninstall cable/hose/UNS
41	Recycle slurry



Table 5. Duration used in Simulation

Element number	Description	Distribution
2	Bring pipes to connecting	TRI (2, 5, 15)
5	Connect / weld pipes	UNI (10, 15)
9	Check pipes connection/welding	UNI (10, 15)
13	Attach pipes to crane	DET (2)
16	Roll pipes to thruster machine	UNI (1, 2)
18	Pipes setup/installation	BETA (28, 80, 0.761, 1.841)
26	Mix lubricants	TRI (25, 30, 35)
31	Empty spoil tank	TRI (20, 30, 35)
36	Uninstall cable/hose/UNS	BETA (7, 33, 0.643, 3.020)
41	Recycle slurry	TRI (10, 12, 15)
6	Dummy	DET (0)
14	Lift to guard rail	DET (1)
20	Crane returns	DET (2)
23	Thrust pipes	DET (40)

Table 6. Resource cost information

Resource	Costs ($)
Pipes	5600/section
Crew A	44/hr
Crew B	40.8/hr
Crane (+ operator)	61.45/hr
Thruster system	550/hr
Backhoe (+ operator)	27.9/hr
Truck	51/hr
Water	17
Bentonite	21.6
Lubricants	28

Simulation Result

A total of 12 cycles simulation were performed with the Cyclone model. The result of productivity per time unit is 0.1894977 for total simulation of 1266.5 time unit. It gives the productivity rate of 0.208 meter/minute or 12.48 meter/hour.

Considering the cost of resources, the achieved productivity rate takes US$ 5,706/meter.