The present invention relates to a process for building a concrete structure in loose matter, from ground level, by use of a rotatable erosion head and a grouting head providing with a drill bit, of the kind disclosed in SE-B-433 639, and as stated in more detail in the preamble of the independent process claim 1 below. The invention also relates to equipment for carrying out said process and of a kind as stated above.
The present invention relates to building permanent structural elements in loose matter without necessitating any preliminary conventional digging operations and temporary safety measures.
Slightly generalizing, we can say that most processes used to day for building permanent structural elements in loose matter constitute relatively small improvements of processes which where introduced 40 - 50 years ago. Present technology is also based on a large percentage of manual labour, resulting in high total cost, e.g. due to digging, boarding, and casting one section at a time. Expensive temporary structures, e.g. for injection, and earth reinforcements, braced sheet pile walls, must be erected before the permanent structure can be established.
The advantages of the process according to the present invention are due to the fact that it permits drilling down into loose matter from ground level, either indoors or outdoors, irrespective of the kind of soil, to the necessary level for erecting water-proof and permanent structures. Upon completing the structure in the ground the only wounds in the terrain visible on the surface will be moderate "pinpricks", i. e. holes with diameters in the range of 15 cm.
The process and equipment according to the present invention will render a series of other conventional operations redundant, e.g. soil stabilizing operations, like freezing, injection, digging, boarding, casting, also pumping wells, ground compensation and compensations for inconvenience. Also, a reduced construction period is achieved.
According to the invention the above mentioned is achieved by the aid of the features stated in the characterizing part of the independent process claim 1 below as well as subsequent claims, and by the aid of the equipment with features as stated in the characterizing part of equipment claim 4 below and following claims.
When a tunnel structure is built in the ground by the aid of processes known to day, loose matter remaining inside the tunnel is dug out. This means that a concrete shell is provided, from which loose matter must be removed after hardening. With present technology it is practically impossible to build a tunnel in loose matter without extensive digging operations and operations to stabilize loose matter.
The process and equipment according to the present invention is also well suited for building tunnels (culverts) below existing railway tracks and roads without interfering with traffic on the crossing railway or road line. With present methods these are problems which could only be solved by temporary by-pass roads or by-pass tracks, which are expensive arrangements per se.
The present invention is disclosed in more detail below with reference to the drawings, in which
Figure 1 shows the equipment in the position reached upon drilling down into the ground, before erosion of the drilled hole and grouting of the bore hole which is expanded by erosion.
The equipment comprises two units, i. e. an erosion unit 2, and a grouting unit 3 for grouting with concrete.
The erosion unit comprises an erosion head 2a with a drill bit 2b provided lowermost. Above the latter an erosion nozzle 2c is provided and comprises a water nozzle which is surrounded by an air nozzle for ejecting a radial jet stream of water and air. The erosion unit, furthermore, comprises a guiding tube 8 on which the above mentioned components are mounted and through which water and air conduits extend to feed said erosion nozzles 2c. Guiding tube 8 is mounted in a bearing 8a to be raisable and lowerable as well as rotatable, and rotating motor 8b is provided in a frame 6a. Guiding tube 8 is at its uppermost end connected to supply conduits 10 and 11 for water and air, respectively, via a swivel means 10a.
Grouting unit 3 with grouting head 3a and drill bit 3b is rotatably and raisably as well as lowerably mounted in a bearing 9a, and rotating motor 9b is provided in a frame 6b, and unit 3 is at its uppermost end connected with a supply conduit for concrete, via swivel means 11a.
Together, frames 6a and 6b constitute a rack 6 with adjusting means 7 of mutual spacing between frames 6a, 6b. Rack 6 is intended for adjustable attachment to a rig F, e.g. a caterpillar rig, as shown in Figure 2, by the aid of means F₁ known per se, permitting the equipment to be raised and lowered as well as inclined by the aid of pressure cylinders in a manner known per se, as shown in Figure 2. Erosion head 2a and grouting head 3a may, thus, be independently actuated for lowering, raising, and rotation, respectively. Frames 6a, 6b are movable to and from each other for adjustment of the centre-line spacing C between erosion head 2a and grouting head 3a. As shown in the drawings, Figure 1, adjusting means 7 consists of adjustable telescopic rods 7a which connect frames 6a and 6b.
A collar 12 is provided about guiding tube 8 in order to collect and guide eroded loose matter from bore holes in a controlled manner through a mass and density gauge to permit calculation of the volume of the eroded void, i.e. the expanded void. By the aid of adjustable spacer means 7a the center-line spacing between erosion head 2a and grouting head 3a can be adjusted according to the projected diameter of the expanded bore hole 4a.
Grouting unit 3 comprises extendable grouting pipes 9.
In carrying out said process by the aid of the above mentioned equipment, erosion unit 2 and grouting unit 3 are drilled down to rock or portative ground with a predetermined center-line spacing C between units 2 and 3. In order to establish good rock contact only the downwards directed erosion nozzle 2d on erosion head 2a is used. Upon erosion of the rock surface erosion head 2a and guiding tube 8 are pulled up by a raising means, not shown. Pulling up occurs slowly during constant rotation, and simultaneous ejection of highly compressed water and air at a high pressure of 100-1000 bar, from water and air nozzle 2c. Said water jet enveloped by air will break down the particulate structure and dissolve soil in bore hole 4 which is drilled by drill bit 2b of erosion head 2a. An expanded bore hole 4a with a desired diameter is thus formed, its diameter being measurable by the aid of equipment known per se, which is not described in detail here. In this manner a cylindrical eroded void is formed which constitutes said expanded bore hole 4a. Due to the overpressure created by high-pressure jet 5a from nozzle 2c flushed down material E will be urged towards the surface through bore hole 4 and said collar 12. Simultaneously , or upon establishment of void 4a high-grade concrete D is pumped through grouting pipe 9 with grouting head 3a to fill void 4a, which will also cause expulsion up through bore hole 4 of material E which was broken down by flushing. Concrete D may be provided with additives rendering it water-repellent, so that flows in void 4a due to erosion jet 5a will cause a minimum of binder to be washed out from concrete D.
When guiding tube 8 with erosion head 2a and grouting pipe 9 with grouting head 3a are pulled up, grouting head 3a should preferably be positioned at least 0.5 m below erosion jet nozzle 2c if the latter is active, so as to reduce harmful flows in the eroded space which may wash out binder from concrete D.
Bore hole 4 is eroded by the aid of air and water jet 5c to a desired level H while erosion head 2a is pulled up, then erosion is stopped. Grouting of void 4a with concrete D is continued during simultaneous pulling up of grouting pipe 9, until void 4a is filled, which is checked by the aid of eroded matter forced up through bore hole 4. When void 4a is completely filled such matter is replaced by squeezed up cement binder from concrete D.
Figure 3, thus, shows erosion head 2a and grouting head 3a drilled down to a desired depth in ground A and with a finishing downwards directed erosion jet 5b from erosion head 2a to clean the rock ground. When said erosion jet 5b terminates, erosion beam 5a from nozzle 2c is started to expand bore hole 4 and provide the expanded bore hole 4a and, thus, the desired void as shown in Figure 4, with a desired diameter B and a desired height H, as shown in Figure 5.
Figure 4 shows incipient expansion of bore hole 4 during rotation and pulling up of erosion head 2a, whereas supply pipe 9 with grouting head 3a is at rest in a peripheral position in the lower portion of the expanded bore hole 4a.
Figure 5 shows the next step, in which erosion head 2a is pulled up approximately to a desired level H of the expanded bore hole 4, and in which concrete D is supplied through supply pipe 9 to fill up the expanded bore hole 4a. This operation is continued until the expanded bore hole 4a is filled.
In Figures 4 and 5 expanded bore holes 4a with a substantially circular cross section and desired diameter B are shown, which will result in a cylindrical structure of concrete D.
By causing erosion jet, i.e. air and water jet 5a to swing forwards and back across a sector by corresponding rotation of erosion head 2a, a concrete structure with a corresponding cross section may be provided.
By full rotation of erosion head 2a with simultaneous control of the erosion pressure of air-water jet 5 it is possible, e.g. to provide concrete structures having oval cross sections, e.g. oval piles, dependent on the rotational angle of rotating head 2a.
The process according to the present invention may be carried out in all kinds of ground. This process is, thus, applicable in clay, silt, sand and gravel, as well as in most kinds of fillers, moraine, and boggy soil/peat.
In cohesion soils the erosion and grouting process may, if desired, be carried out in two phases, since transitory tensions in cohesion soils will generally prevent the eroded void from collapsing if it is filled with water. There are several advantages of carrying out the erosion and grouting process in two operations:
In friction soils both operations, i.e. erosion and grouting, must be carried out in one operation, since the provided void 4a will generally collapse before grouting with concrete D is completed. The void, i.e. the expanded bore hole 4a, may however be stabilized if a heavy stabilizing liquid, e.g. bentonite, is introduced into the void. Said liquid will, however, tend to mix with the return matter, i.e. the eroded soils and flushing water, so that the extent, i.e. width B of the structure/pile can only be measured by the aid of an acoustic probe or by measuring the volume of concrete D which is cast inside void 4a.
It was mentioned before that the distance between erosion head 2a and grouting head 3a is adjustable by the aid of telescopic rods 7a in rack 6. It is, thus, possible to ensure that grouting head 3a and erosion head 2a receive a desired mutual center distance when drilled down into ground A, causing grouting head 3a to be located in the periphery of the eroded/expanded bore hole 4a, as shown in Figures 4 and 5. Consequently, concrete D which is injected through the relatively thick supply pipe 9 will fill the expanded bore hole 4a from a location at the hole wall and will, thus, expel any eroded matter and water up through bore hole 4.