Sunday, December 12, 2010

Construction Simulation with Cyclone

Applications of simulation on tunneling operations have been previously In 1973, Halpin developed the CYCLONE _cyclic operation network_ format that has become the basis for a number of construction simulation systems. CYCLONE allowed the user to build models using a set of abstract but simple parameters. This system was the basis for a wide range of construction simulation research efforts including tunneling and microtunneling. In 1978, Halpin popularized the use of CYCLONE format with MicroCYCLONE program. MicroCYCLONE is a microcomputer based simulation program designed specially for modeling and analyzing site level processes which are cyclic in nature. Due to the accessibility and ease of use, a Web-based version of MicroCYCLONE, namely, WebCYCLONE maintained by Purdue University is used in this research to perform simulations (Division of Construction Engineering and Management Website 2005).

The CYCLONE methodology is a modeling technique that allows the graphical representation and simulation of discrete systems that deals with deterministic or stochastic variables. Using the CYCLONE methodology for simulation of construction operations, construction processes are divided into discrete pieces or work tasks and their interactions are represented. This type of simulation focuses on resources and their interactions and presents a graphical representation of their interactions.
The basic modeling elements used in the CYCLONE methodology are as follows. These elements are described as follows: combi _COMBI_, represents a work task constrained by one or more resources; counter _COU_, keeps track of the number of
times a unit passes it; function _FUN_, simulation entities can be accumulated at this node; normal _NORMAL_, represents a nonconstraint work task with an infinite number of servers; queue _QUE_, a node where idle resources wait and is always followed
by COMBI nodes; Arc, indicates the logical structure of model and direction of entity flow _Halpin and Riggs 1992_. Resources can be in one of two states—active _denoted by a square element_ or idle _represented by a circle element_. Resources will move between these two states, as they “traverse” from one activity to another. A flow unit traverses a CYCLONE network with the following effects:
• Waits in QUEUE nodes for processing;
• Initiates _or signal_ the processing of a work task;
• Generate other entities where they traverse a QUEUE-GEN node;
• Get consolidated with other flow units when they pass a
CONSOLIDATE Function; and
• Register productions where they pass a function COUNTER
 
Some Examples:


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.