Kyushu University Global COE Program
Journal of Novel Carbon Resource Sciences, Vol. 7, pp. 18-25, Feb. 2013

Development and Application of Ground Improvement
Machinery Chain Conveyor Cutter
Shizuo Ikuta*1,*2, Yoshishige Masuda*1, Kikuo Matsui*2, Hideki Shimada*2,
Takashi Sasaoka*2*1Land Creative Co.,Ltd, Omuta 836-0002, Japan
Department of Earth Resources Engineering, Kyushu University, Fukuoka 819-0395, Japan*2(Received October 30, 2012; accepted January 21, 2013)
Natural ground generally consists of various types of soils and each soil independently reacts with cementing
materials. In order to realize uniform and stable soil ground improvement, it is preferable that the excavated soils arevertically mixed together as a whole. Chain Conveyor Cutter (CCC) is like a chain conveyor but is installed verticallyon a pile driver, sunk into and is raised up from the ground. An 180 kw water cooled electric motor rotates chain
units and enables CCC to cut harder soils at the bottom of the machine discharging cement slurry. The soils andcement slurry are hauled up by the scraper bars of the chain units being mixed together on the way up to the groundsurface, which consequently establishes stable improved ground.

1. Introduction

Conventional ground improvement machineries are
represented by auger type machineries. Mixing paddles
are attached on the edge of drilling rods and cutting bits
are mounted on the bottom paddles. The assembly of arod and mixing paddles with cutting bits called cutting
head is rotated and sunk into the ground. The cutting head
excavates the soils in situ and cement slurry is discharged
through the port installed on the head. The excavatedsoils and discharged cement slurry are mixed together.
The sinking speed of the cutting head is managed atmost 50 cm per minute considering the mixing abilitiesof the cutting heads, so that the vertical movements of cut
soils are limited and the soils are remained at verticallyoriginal position with mixed cement called soil-cement.
The physical properties of soil-cement depend on thesoil types and cement mix design. There occur various
types of soils in natural grounds and also in artificially
reclaimed grounds. The strengths of soil-cement aregoverned by the weakest strata and the impermeabilityof the soil-cement walls are by coarse materials. With
respect to the cement mix design, the volume of cement
every 1 cubic meters of soil in situ is determined basedon the weakest strata and/or most permeable strata
which require the largest amount. The volume of wateris also designed based on the mixing properties of strata.
Cohesive clayey strata are sticky and require extra
amount of water.
The cutting ability of the conventional auger type
machineries is limited that the available groundconditions are limited to more or less 20 in N value.
When those machineries come across harder ground,
different auxiliary measures have to be taken. In casethe machinery manages to penetrate the harder grounds,
drilling rods tend to deviate due to their low rigidity,
especially in the case of gravel rich grounds, which
requires deliberate and skillful operation.

The cross section of soil-cement column constructedby the conventional auger type machineries is circular.
Using circular columns, independent circular columns,
walls, grid patterns and entirely improved grounds areconstructed. Considering the column walls, for instance,
the wall thickness is not constant and peripheral part ofthe circular column is in vain.
Ground improvement works with conventional auger
type mechanical soil mixing is indispensable but contains
intrinsic disadvantages as mentioned above. The groundconditions available for the conventional auger type
machineries are therefore restricted from the view pointsof their mixing and cutting abilities.
On the other hand, chain saw type machine wasdeveloped and has been put into use specifically forconstructing continuous underground walls. The
working method using chain saw type machine is named
Trench Cutting Re-mixing Deep Wall Method (TRD)1).
The machinery TRD consists of a main body, ashifting apparatus and a hydraulic unit and is exclusively
used for the continuous and straight wall construction,
not for single columnar shaped structures. The main
body is placed underground and horizontally moves
forward while cutting and mixing the soil in situ withcement slurry which is discharged at the bottom of themachine. The TRD wall is same in thickness and hasvertically uniform properties. The maximum depthof the wall reaches 50 meters. The machine TRD is
special purpose machine for constructing undergroundstraight continuous wall. Then, longer the wall is, themore cost effective. But TRD method is ineffective forconstructing discontinuous ground improvement works
like independent columns, grid patterns and polygonal
walls.
To make up for the disadvantages of the TRD,
Chain Conveyor Cutter (CCC) was developed for both
continuous and discontinuous ground improvement- 18 -

Journal of Novel Carbon Resource Sciences, Vol.7, Feb. 2013

works making use of the technology of underground coalmining equipment and experiences2). CCC is like a Chain
Conveyor but is installed vertically on a pile driver andis sunk into the ground. An 180 kw water cooled electricmotor enables the machine to cut harder ground at thebottom of the machine with cutting bits on the chain
units and rotating chain units mix the soil. The soil andcement mixture is hauled up by the scraper bars andconsequently vertically uniform rectangular columns
are established.

Drive units are electric motors located head end and,if necessary, tail end. In the actual operation of mining
faces, the chain conveyor is forced to start runningunder fully loaded condition. In such cases, the starting
torque reaches more than 200% of nominal torque. Oncethe conveyor succeeds starting, the torque decreases
drastically. This characteristic driving performanceis essential for CCC considering the unexpected
hard materials to come across and irregular groundmovements.

2. Development of CCC

2.3 Roadheader

2.1 Concept of CCC

Concept of CCC is to establish quality oriented ground
improvement and safe and flexible operation. The qualityof the ground improvement includes uniformity of the
improved bodies, low cement consumption, saving wastematerials and the days to be worked, which require
strong cutting ability, vertical mixing mechanism andrigid body of the machine.
Ground improvement machineries generally deal
with soft grounds. The soft grounds ordinary consist ofsoils of less than 20 in N value. But, natural grounds are
not necessarily uniform and soft enough to deal with.
Artificial reclaimed grounds are likely to contain various
materials. It is not always natural gravels and boulders
but also manmade materials like debris of concrete.
Unexpected ground movement could hold the machine.
CCC is to be provided sufficient driving power anddurability for enabling the machine to afford versatile
ground conditions and cost effective performances.

Ground improvement machinery generally deals withsoils and cutting ability of such machineries are limited
to more or less 20 in N value. But, ground improvement
works include adverse conditions like gravel rich groundand artificially reclaimed land where unpredictablematerials could occur. Coal and rock cutting machinerypresents useful design criteria of chainsaw type machine.
Roadheader is one of the typical coal and rock cutting
machinery first developed in 1950s for roadway drivage
and coal winning works in coal mine. Nowadays,
roadheaders are widely applied to soft to medium strengthrock cuttings in mining and tunneling operations3) (Fig.
2).
Considering the CCC cutting design, the cutting forces
and normal forces of the roadheaderes present universal
standard. According to the figures presented, the cutting
force of 150 kN and the normal force of 200 kN are
considered key forces to handle hard materials.

2.2 Chain conveyor
Chain Conveyor is commonly used for transporting
materials like coal at production faces in undergroundcoal mine. Fig. 1 shows a chain conveyor installed in
longwall mining face. The transportation capacity ofcurrent chain conveyors exceeds more than 1,000 tons
per hour and the conveyor length is more than 200 m.
Short link chains are adopted and twin strand chain
system is preferred. According to the running position,
twin strand system is classified into outboard or center
type chain system. Chain connectors are well developedand supporting high capacity transportation system.
Na
tiv
ec
50
oal
m
bed
～
25
0m
Coal shearer

Belt conveyor
Stage loader

Goaf

CrusherFace conveyor
Chain conveyor

Fig. 1 Chain Conveyor in Longwall Face.

Fig. 2 S300M Roadheader.

2.4 Prototype CCC (Fig. 3)
Applying the subsidy of Omuta City, Fukoka Pref.
Japan, a prototype CCC was developed in 2000. The
specification and main structure of the CCC are as
follows:
1) The CCC consists of a driving unit, a middle section
and a return unit from the top of the machine indescending order.
2) The cutting depth is 10 m and a cross section of cuttingarea is rectangular 0.75 m wide and 1.0m long.
3) The capacity of a drive motor is 55 kW and planetary
gearing system is adopted making use of its reliability
and compact design.
4) The drive unit is located on the upper most part of- 19 -

Development and Application of Ground Improvement Machinery Chain Conveyor Cutter

the machine when installed on the pile driver. The
power is transmitted through the drive sprocket wheel
to twin outboard chains which are connected by theconnecting plates (scraper bars). On each scraper bar,a bit plate is mounted where the conical shaped cutting
bits are installed with designed arrangement, which iscalled bit unit. Fig. 4 conceptually explains the bit unitof CCC.
5) A chain tensioning system is equipped and a set ofpulleys are mounted on top of the drive unit for lifting
the body using a main hoist of the pile driver.
6) On the side of the drive unit, a connecting apparatus is
attached to allow smooth movement on the leader postof the pile driver.
7) The middle section consists of four middle posts
designed rectangular shape. For preventing thesnaking of the chain units and for lifting the soil andcement mixture, plates are welded at both sides of each
middle posts.
8) Abrasive wear proof steel plates are adopted for thepan of the conveyor trough.
9) The middle posts are connected with bolts each otherand two parallel 50 A pipelines are installed inside theposts to pump cement slurry or other materials fromthe inlet port placed upper post down to the discharge
port placed on the return unit.
10) Specially designed pipe joints are adopted forpreventing the leakage of pumped materials.
11) On the side of each middle post, tubular guide rails aremounted to connect with a guide holder equipped at
the bottom of the leader post of the pile driver.
12) The return unit is located at the bottom of the machine.
The cutting bits mounted on the bit plate cut the soils
while running along the return unit as shown in Fig.
5. Faster the CCC is being sunk and/or harder the soils,
severer impact loads are generated. The elements ofreturn unit are given sufficient strength and durability and the sealing system is designed tight enoughagainst soil and cement slurry mixtures.
Drive unit
55kW×4P/8P
Connecting
apparatous
50A
Pipe lines

Middle post
4 pieces

Conical bit

Bit plateFig. 4 CCC Bit Unit.

CCC Return Unit

Fig. 5 Prototype CCC at Site.

2.5 First trial work
In the same year 2000, the first trial work was carriedout using prototype CCC and four soil-cement columns
were constructed without any trouble. Fig. 5 shows the
prototype CCC at the first working site.
In this first trial work, the cement factor was 200 kg/
m3. The boring cores taken from different depth of eachcolumn showed the uniformity of the mixture of soil andcement and the uniaxial compressive strengths (UCS)
satisfied predetermined target of 1.0 N/mm 2 as shown in
Table 1.
Table 1Tubular guide rail

Guide holder

1,000

CCC Cutting Bit

General View of CCC

Return unit
750

Twin outboard chain

Scraper bar

Pile driverFig. 3 Assembly Drawing of Prototype CCC.

- 20 -UCS of the Column (N/mm 2)

Depth
(m)

Column1

Column2

Column3

Column
4

2

6.4

4.4

4.1

4.0

4

6.2

8.0

3.3

2.6

6

7.8

9.5

2.3

1.8

8

-

6.8

2.3

1.3

10

-

7.9

2.0

2.0

Water/Cement
(%)

100

100

200

200

Journal of Novel Carbon Resource Sciences, Vol.7, Feb. 2013

2.6 Crane version CCC

Table 2

Based on the first trial work, a crane version CCC
was developed assisted by Ariake National College ofTechnology in 2003 (Fig. 6).
In the case of conventional auger type machineries,
horizontal rotation requires rigid holding apparatus toresist counter force of the rotating cutting head. The
vertical movement of CCC does not generate horizontal
moment that the crane version of CCC was consideredfeasible. The joint study and test work titled “Compact
Lightweight and Multi Purpose Type Ground Excavator
CCC” proved the feasibility of crane version CCC.

Drive motor

Specifications of CCC and HCCC
CCC

High power CCC

55 kW air cooling

180 kW water cooling

Direct online start(Pole change)

Inverter drive(Variable frequency
drive)

Machine length

16 m

28 m

Machine weight

23 ton

28 tonRectangular 0.75 m2

Rectangular
0.9 ～ 1.2 m2

Shape ofexcavation

0.75 m×1.0 m

0.75 ～ 1.0 m
×1.2 mDepth ofexcavation

10 m

20 m

Chain typeTwin outboard
19 mm ϕTwin outboard
22 mm ϕChain tension

7 ton

23 ～ 60 ton

Chain speed

25 or 50 m/min

0 ～ 60 m/min

2.8 Field application and machine modification

Fig. 6 Crane Version CCC.

2.7 High power CCC (Fig. 7)
Subsequently, the development works of a commercial
base CCC named “High Power CCC” (HCCC) werecommenced and the first machine was manufactured in
2005. The specification of HCCC is compared with CCC
in Table 2.

Fig. 7 High Power CCC.

The records of HCCC field application and the machinemodification are as follows:
1) In October 2005, HCCC excavated undergroundcontinuous walls constructed by prototype CCC in2003 in order to return leased land to Omuta City.
2) In April 2006, HCCC was applied to the test
excavation of the concrete mass at Noda City, Chiba
Prefecture.
3) In June 2006, HCCC attended the test work ofwithdrawing concrete piles already installed
underground at Nagano City, Nagano Pref.
4) The UCS of the wall at Omuta City and the concrete
mass at Noda City were 3 N/mm2 and 27 N/mm2
respectively. The sandy sediments surrounding theconcrete piles at Nagano City contained a lot of hard
gravels. The conditions of these three working sites
were beyond the ability of conventional auger type
machineries. HCCC showed the feasibility underadverse conditions but presented a new problem on
the return unit. Then the return unit was redesigned
and manufactured.
5) In 2007, HCCC constructed impermeable walls anddestructed the walls constructed by HCCC itself.
The specification of the walls was 0.85 m thick, 8 to
9 m deep, total 311 m long and the overall wall area
was 2,700 m 2.
6) The working condition of the site was much worse
than expected and HCCC suffered severe damages
due to the obstacles like PC piles and reinforced
concrete structures. These damages made it clearthat more sophisticated chain speed control system
and modifications of bit arrangement are inevitable
for more smooth and effective bit attacks to the soils
in situ. As a chain speed control system, inverter- 21 -

Development and Application of Ground Improvement Machinery Chain Conveyor Cutter

drive system (variable frequency control system) was
developed and introduced to HCCC. The inverter
control system enabled HCCC non step continuous
chain speed control which is of great help for safe
and sound operation.

2.9 Summary of HCCC structure and movement
Summarizing the above, the structure and movementof HCCC are as follows. As shown in Fig. 8, HCCC
consists of a drive unit, a middle section and a return unit
from the top of the machine in descending order. The
drive motor is 180 kW inverter drive and middle section
consists of a number of posts according to the depth of
the ground to be improved. The cutting depth is up to 20
meters. The cutting bits cut the soil while running along
the return unit. While HCCC is being sunk discharging
cement slurry, the cutting bits run at maximum 60 meters
every minute (Fig. 9). The scraper bars connecting twin
outboard chains scrape up, agitate and mix the cut soil
with cement slurry, which is named “conveyor effect”.
There exists only small room for the soil and cement that“conveyor effect” works and the soil and cement is raised
up to the ground surface.

Fig. 8

Conceptual Diagram of HCCC.

On the other hand, scraper bars running down to thereturn unit convey raised soil and cement slurry down to
the ground. Once HCCC reaches to the predetermined
depth, slurry pump is stopped, CCC is raised up to thesurface and the void is filled with the mixture of soil
and cement. As a whole, the soil and cement behavescomplicated movement which enables CCC to establish
high quality improved bodies.

3. Working record of HCCCIn Feb. 2007, the planning subcommittee of theport deliberation council in the Ministry of Transport
approved the Port of Miike Restoring Plan whichcontains widening and deepening shipping lane of theport. According to the plan, restoring work was started
and two settling ponds were constructed for receiving
and treating dredged materials.
HCCC constructed cut-off walls surrounding theponds to block water seepage from inside the ponds. The
land, where the ponds were constructed, was reclaimed
by Miike Coal Mine, closed in 1997. Therefore, theground consists of natural rocks like sandstone, shaleand silicate fossil rocks. Those rocks were weathered but
still maintain the strength and porosity as a whole. Fig.
10 shows typical columnar sections of the ground where
hard materials exceeding 50 in N value are observed.

Fig. 10

Typical Columnar Sections of the Ground.

3.1 Method of wall construction

Fig. 9 Conceptual Diagram of HCCC Movement.

Under these difficult ground conditions, the time andcost available for constructing cut-off walls were limited
and the land owner wanted to re-use the land afterwards.
Conventional sheet pile walling is one of the methods
but was not applied to this site due to the existence of
hard materials and considering the re-use of the land.
Conventional auger type method is difficult to handle
hard ground.
In 2007, HCCC constructed cut-off walls and removed
those walls by itself at the neighborhood of the proposedsite. Evaluating this result, HCCC cut-off walling wasselected.

- 22 -

Journal of Novel Carbon Resource Sciences, Vol.7, Feb. 2013

3.2 Working record
The reclaimed land consists of weathered coal mineorigin rocks placed directly on the sea floor.
The sea floor is thick clay rich seams named Ariake
Nendo Seam which is considered impermeable having
the hydraulic conductivity of more or less 1×10 -6 cm/sec.
Japanese standard defines the hydraulic conductivity andthickness of the impermeable ground of the landfill site
as 1×10 -5 cm/sec and 5 m respectively4). The hydraulicconductivity and thickness of the Ariake Nendo Seamat site satisfied the landfill standard. Then, the cut-off
walls were designed to penetrate into the sea floor andthe requested hydraulic conductivity and the wall thickness are 1×10 -6 cm/sec and 0.75 m respectively based on
the standard of final landfill site of Japan.
The specification of the first pond was 0.75 m thick, 7
to 8 m deep and 1,128 m long in total. The overall area
was 8,470m 2. That of the second pond was 0.75 m thick,
8 to 10 m deep and 1,197 m long and the total area was
10,420 m2. Laboratory tests were conducted using boringcores taken at site and the mix design was decided asfollows:
1) Type of cement
Blast furnace cement
2) Cement factor
1st pond 150kg/m3
2nd pond 200kg/m3
3) Water/cement ratio
1st pond 150%
2nd pond 100%
The productivity of HCCC works was approx. 200 m 2/
day and the core samples taken from the constructed wall
satisfied the design value as shown in Figs. 11 and 12.

utilizing conveyor effect.
On the other hand, filler soils are charged while HCCC
is raised up to the surface. The conveyor effect works
and the filler soils are moved down to the bottom of
the machine. When HCCC reaches on surface, the void
excavated by HCCC is filled with filler soils and the soils
are completely replaced.
Sand columns are well established using this function
which is considered effective as one of the preventives ofground liquefaction.
When considering ground improvement works, thisfunction is helpful for designing physical properties ofimproved soil-cement bodies. Organic soils, like peat, aregenerally difficult to improve and requires high cement
factor5), amount of cement added to unit volume of theground. By changing the composition of the original
ground, withdraw some part of original ground and add
soils from outside, various types of soil-cement bodies
are constructed. The mix design is to be conducted basedon the required properties like strength or permeability
by mixing original soils and filler soils together, which is
new concept of the mix design.

4. Functions of HCCC

4.1 Flexible cutting method
HCCC is equipped with an inverter drive 180 kw
electric motor and the chain unit is driven by the pulling
force of max. 55 ton. Fig. 13 explains HCCC cutting
method of constructing continuous soil-cement body,
like cut-off wall, square block body, etc., but not single
column. Ordinary cutting method laps each unit for
20 cm and an effective advancement is 1 m. When theworking ground is hard and is not advantageous to lap
20 cm, HCCC changes the laps and decreases the cutting
resistance as shown in Fig. 13 in order to maintainproductivity.
In addition to the variable chain speed and strong
cutting force, the flexible cutting method enables HCCC
to apply difficult ground conditions and to excavate andrestore improved soil-cement bodies.

Fig. 11

Hydraulic Conductivity of the 1st Pond.

4.2 Soil replacement
Besides constructing soil-cement improved bodies,
HCCC replaces soils in the ground. Fig. 14 explains thesequence of HCCC soil replacement. When HCCC ispenetrated into the ground without discharging slurry,soils cut by the running bits around the return unit, atthe bottom of the machine, are lifted up to the surface- 23 -

Fig. 12 Hydraulic Conductivity of the 2nd Pond.

Development and Application of Ground Improvement Machinery Chain Conveyor Cutter

The U.S. Environmental Agency published a reporton Permeable Reactive Barrier (PRB) technologies forcontaminant remediation in 19986). Fig 16 shows one of
the PRB systems named funnel-and-gate system. The
funnel-and-gate system consists of funnels and gates.
The impermeable funnels lead polluted groundwater(GW) flows to permeable gate where reactive materials
are placed. The flexible cutting method and the functionof material replacement are available for constructing
PRBs and emplacement of reactive materials into thereactive gate. When applied to PRB construction, HCCC
construct water tight funnel walls and a gate block usingsoils in situ and cement first, as shown in Fig. 17. Then,
HCCC excavate the solidified soil-cement gate block andfill the void with reactive materials. This way of thinking,funnel and gate system, is applicable to landfill site
inspection wells. If inspection wells are combined withfunnels, funnels collect leachate to the well and wider
area is monitored by each well, which will improve thesafety and the reliability of the final landfill site system.

Fig. 13 HCCC Cutting Method.

Fig. 14

HCCC Replacement Method.

5. Prospect to the Future

Making use of the characteristic cutting and mixing
abilities and its conveyor effect, various types of soilcement structures are expected. Fig. 15 is one of theconcepts for constructing final landfill site on the ground.
At first, HCCC construct artificial impermeable soilcement ground using original ground. After constructing
embankment on the artificial impermeable ground,
HCCC construct water tight wall in the embankment.
This landfill site can be combined with sheeting system.
Such hybrid system is located above the original groundlevel, so that water leakage from embankment isdirectly observed if happens. The basement of landfill isconstructed not only water tight but also seismic resistant,which is advantageous for reuse of the final landfill site.

Fig. 16

Conceptual Diagram of Funnel-and-Gate.
1. Construct CCC walls for funnel

2. Construct CCC block for gate

3. Excavate and fill reactive material

Fig. 15 Conceptual Diagram of HCCC Landfill Site.

Fig. 17- 24 -

Sequence of CCC Funnel-and-Gate construction.

Journal of Novel Carbon Resource Sciences, Vol.7, Feb. 2013

6. Conclusions

References

Chain saw type ground improvement machinery CCC
constructs high quality soil-cement body using verticalcutting and mixing functions. Conveyor effect plays
important roles for preventing entrained soil circulationand for maintaining uniform mixing. Cutting bits cut
soils at the bottom of the machine while travellingaround the return unit. The cutting force is utilized by
the limited number of bits around the return unit that
hard soils exceeding 50 in N value is workable, whichenables CCC to restore improved soil-cement bodies.
The function of replacement is helpful for improving
difficult soils like peat and saves the cement consumption.

1)
2)
3)
4)

5)
6)

Acknowledgements: The authors would like to express
sincere thanks to those who assisted us to develop andapply CCC to the actual field works and gave us future
prospect of CCC applications.

- 25 -

M. Mizutani, Kobe Steel Engineering Report, 57(1), 96(2007).
H. Furukawa, Journal of MMIJ, 105(11), 808 (1989).
N. Kashiwamura and K. Sasaki, Journal of MMIJ,
106(11), 636 (1990).
Ministry of Health, Labor and Welfare, Ministry of Internal Affairs and Communications, Amendment Orderof Technical Standards in terms of Non-industrial andIndustrial Disposal Final Landfill Site, 16th June, 1998.
(in Japanese)
Public Works Research Center, Design and Operation
Manual of Deep Mixing Method for Land Works, Revised Edition, p.35 (2004). (in Japanese)
United States Environmental Protection Agency, Permeable Reactive Barrier Technologies for Contaminant Remediation, EPA/600/R-98/125 (1998).