Micropiles are often used for the underpinning of foundations of pre-existing structures in order to preserve them for various reasons, whether historical, cultural or related to stability.
They can provide structural support, enhance mass stability and transfer loads. Accordingly, micropiles can also guarantee the stability of slopes, while horizontal micropiles can be used for tunnel construction as support for the arch roof and sides.
Simply put, micropiles are small-diameter piles that do not exceed 300mm in diameter, compared with large-diameter piles that go up to 3,000mm. Due to the small size of the piles, the rigs themselves are often more compact and lighter, and this also goes for ancillary equipment like grout mixers and grout pumps.
"Big advantages of micropiles are their high carrying capacity, less site constraint problems and self-sustained operation," explains Pierluigi Sanchi from Fraste's sales department.
Marco Rapuano, sales director for micropiling and georesources at Soilmec, says: "Micropiles can penetrate to hundreds of feet in depth, and each of the piles can support many tonnes of load. Maximum depths can easily exceed 100m."
Small sites where heavy plant is not allowed, noise-vibrations restrictions apply and/or headroom is limited are particularly suitable for micropiling rigs. This could include job sites like basements and gardens, which simply can't accommodate heavy machinery.
The needs of piling and foundation contractors when it comes to equipment vary greatly, and many are asking for higher productivity in more complex settings, as well as larger drilling diameters offered by compact drill rigs.
Clients will naturally need different solutions for different job-site conditions. Sanchi notes that Fraste will sometimes get requests for small machines with high torque and force, and other times a larger one, when the client doesn't have any issues with low-overhead restrictions.
"There is a clearly noticeable trend where our clients are looking for our compact-class drilling equipment," adds Siggi Ottersbach, sales director and product manager of German Hütte Bohrtechnik. "A lot of jobs have to be carried out as refurbishment and upgrading projects in already existing buildings or on existing structures, e.g. stabilising of foundations and carriageway additions on bridges."
In this sector it is also necessary to have the certainty of being able to carry out any works, in any direction, without having to worry about the stability of the drilling rig.
While micropiling methods have not changed much over the years, clients are still interested in the latest technologies that will ease their jobs while also boosting safety and reducing their environmental footprint, including radio remote controls, rod-handling systems and energy-efficient drive systems.
Fraste drill rigs typically used for micropile installation are hydraulic rotary (electric or diesel) power units. They can be track-mounted, allowing for manoeuvrability on difficult and sloped terrain. The size of the track-mounted drills can vary greatly, with the larger drills allowing use of long sections of drill rods and casing in areas without overhead restrictions, and the smaller drills suitable for work in lower-overhead and harder-to-reach locations. Th smaller rigs can be connected with long hoses to a separate hydraulic rotary power unit; this allows placement of the power unit outside the area of work, thus reducing space requirements, noise in the work area and problems with exhaust removal.
Hütte Bohrtechnik's compact class drill rigs HBR 202, with integrated electric motor or diesel engine and HBR 203, with separate E or D power-pack, were designed to fulfil clients' need for small drill rigs with large diameters.
The rigs are especially designed for difficult drilling conditions in confined and limited areas, which require particularly compact and mobile equipment, but at the same time drilling big diameters of, for example, up to 324mm and 406mm.
The compact-class Hütte drill rigs HBR 202 E/D and HBR 203 E/D are self-contained, fully hydraulic crawler drill rigs, which feature a compact and robust design, simple controls, as well as high efficiency. They incorporate the latest diesel technology (Step IV/Tier IV Final), meeting the strict emissions regulations in the EU and US. Furthermore, the units provide a modern and operator-friendly hydraulic system. All movements of the drilling unit are softly controllable. An automatic temperature control ensures an optimal operating temperature even under difficult conditions. The stepless adjustable tramming speed provides a versatile and mobile machine movement.
Both types are fully radio-controlled, which ensures an operation from various positions and control of the drill rig according to the latest safety requirements.
The drill rigs are equipped with telescopic undercarriages that can be extended from 740mm to 1,200mm, as well as a telescopic drill mast with a length of 2,530-3,770mm, and an overall feed length of 1,200-2,200mm. Clamping and breaking units for a maximum diameter of 406mm can be applied, whereas, as per client's demand, also bigger size clamping units up to 610mm have already been incorporated. Together with the powerful rotary head type HG28, which can achieve a maximum rotation speed of 82rpm and a maximum torque of 27,000Nm, which is a very compact and powerful rotary head, the Hütte rigs are suitable for big-diameter surface drilling jobs, which require high torques.
The further development of the KR 702-2R confined-access drill rig has allowed Klemm Bohrtechnik to introduce some exciting new technologies. It was designed and built around the demands for a powerful yet compact micropile drill.
The KR 702 series has been available from Klemm for many years. The technical concept is based on a separation of the drilling unit with a telescopic mast and the drive unit. This makes the drilling unit very suitable for use in confined spaces. With the latest version Klemm has implemented today's requirements for exhaust gas aftertreatment and the revised drilling rig safety standard.
The first type of the KR 702-2R drilling rig was launched on the market over a year ago to selected customers and was tested and evaluated under construction site conditions. The advantage for the customer and the performance gain with this generation results from the introduction of the radio remote control. It turned out that reservations were unfounded and the control system was highly reliable. Basically, it is the evolution of a very recognized machine to make something good even better.
Starting with the power pack, Klemm has introduced a new diesel engine and exhaust system.
According to the latest European and US emission standards - EEC97/68 EC Stage 4; USA EPA/CARP Tier 4 final - yhe KR 702-2R now carries a Cat C4.4 ACERT diesel engine with 117kw at 2,000rpm SCR only, no diesel particulate filter (DPF) needed.
Compliance with the most stringent emission standards gives the operator the confidence when bidding for projects of being within all regulatory standards. An all-electric power pack PP 55E1 is also available. The goal to ensure the interchangeability between electric power packs and diesel-driven power packs was achieved. This also took into consideration that the machine can be operated by a smaller power pack in accordance with EEC97/68 EC Stage 3a; USA EPA/CARP Tier 3 in regions where sulphur-free fuel is not available.
Three different chassis are available for the power pack, large rubber wheels, hydraulically driven tracks or a base frame with forklift pockets.
The hydraulic pumps have been re-engineered to increase the pressure settings from a 210bar level to 310bars. This enables an increase of close to 50% more torque output from the rotary heads and drifters. These new larger load-sensing pumps set at 130L/min and 100L/min offer good hydraulic flow to ensure an optimal oil supply for Klemm rotary heads and percussion units. This increase of torque has been achieved within the same compact dimensions of the rotary and drifter units.
Standard extension hoses between the base rig and the power pack come in 2m for transportation and 20m for job sites. An extra-long 40m hose package can also be installed.
A large variety of possible drill masts, ranging from telescopic to fixed masts, that are either cylinder or drive gear driven, offer a high level of customisation. Depending on the type of work, i.e. low headroom or longer micropiles, the customer can equip the KR 702-2R according to the needs of their project. The largest single clamp range reaches 20in (508mm), and the double clamping and breaking units were upgraded to handle a possible 14in (356mm) casing size for micropile applications. Rotary heads with maximum torque setting of 24kNm and mid-sized drifters with torque setting of 16.7kNm and single blow energy of 500Nm show the strength on this relatively light weight drill rig at 4.9tons. These features go hand in hand with the availability of off-hole slides in order to allow for the free passage of additional winch ropes when handling rebar cages. The overall width of the base rig with its telescopic undercarriage ranges from 750mm up to 1,250mm. In regions where interlocked guards (cages) around the drilling area are compulsory, pre-welded mounting plates allow for the addition of such safety guards. The additional pressure sensitive devices (tripping lines) on either side of the drill mast remain in place to stop the drilling functions when activated.
The new lightweight (approximately 3kg) radio remote control system has replaced the fix hydraulic control panel. The drilling operation can now be carried out from the best position for the drill rig operator. Independent of the actual position of the drill rig, the operator can position themselves in an area free of drill spoils and with increased safety in mind. This offers advantages especially in confined drilling spaces.
Since the same remote-control unit is utilised in all Klemm rigs, a substitution or swapping of control units in case of damage can be easily done. This feature offers advantages in fleet management and rig utilisation. The radio remote control includes the mode selector for ROM (restricted operating mode) and SPM (special operating mode) in accordance with the current standard EN 16228.
The MM8, which is the bigger version of its MM4, is the Massenza's new compact, but powerful drilling rig for civil engineering works such as micropiles, anchors and consolidations.
What differentiates it from the other drilling rigs, Massenza explains, is its special support for the mast: due to an innovative system of cylinders and rotary table, it allows to drill in all directions and in sites with even the most difficult accesses and manoeuvring areas.
Moreover, the combination of its sturdy and balanced frame, with appropriate crawlers and resistant front leg stabilisers gives the MM8 maximum stability during all operations.
The rig is powered by a Deutz 156hp diesel engine Tier 4 Final. It is equipped with a 12t capacity mast, and has a feed system by means of cylinder and heavy-duty high resistance chain that provides a pull-up capacity of 8.15t or, alternatively, a special upgraded mast with up to 10t capacity.
What makes the work easier is also the fact that the MM8 has a remote control for tracking and full drilling operation controls, which allows the operation of the drilling rig from a safe distance and gives the operator the freedom of movement and best view for tracking the machine through all site situations.
The heart of the MM8 is its advanced hydraulic circuit, composed by four hydraulic pumps, two of which are axial piston pumps with variable displacement, one in close circuit only for the rotary head and one in open circuit for the pull up, winches and mud pump.
Massenza says it works with a focus on flexibility and customisation, in order to answer to all clients' needs. The MM8 can indeed be equipped with a wide range of rotary heads, water and mud pumps, winches and rod-handling systems.
Due to the versatility of its components, the MM8 is also suitable for auger drilling, horizontal and upraise angle drain holes, and deep-core drilling up to 450m with a high-performance coring head with free passage chuck and speed up to 1,200rpm.
Soilmec micro-drilling rigs, which cover all drilling methods, can be equipped with a modular mast or moto-reducer crowd system, and can be fitted with a control board or full remote control. The undercarriage with fixed, extendable or oscillating frame with steel or rubber shoes are suitable for all job site conditions.
The drilling rigs have been designed in compliance with the new European Standard EN 16228. Protective cages have been installed to ensure the operator the best accessibility and productivity.
Soilmec's new sound-proofed canopies are designed to reduce the noise and increase accessibility during the maintenance.
The latest technical advancement is the Soilmec solution on its SM-22 to improve the productivity and safety in tunnelling projects.
The designers worked together with the customer, from the technical managers to the operators of the unit, to develop this solution.
It comprises new kinematics; a new rod and casing loader installed on the mast and a new service rack; and a new articulated boom crane with a manipulator for rod and casing.
The new kinematics allow the rig to drill up to 60m horizontally on a tunnel's face in fully automatic mode.