Hand Boer "HDT-5"
The most powerful and durable in its class

(delivery anywhere in the world)

Selection of equipment

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All the equipment is provided on the website of the unified, this means that the rods and other elements from all sections are compatible with each other.
Data for configuration of the hand boer HDT-5 for creation of widening
Equipment Price, $ (€)
Widener (Underreamer) 121.43 (106.25)

Selection of parameters (see fig. 1)

 When ordering, you must specify 4 parameters of the Widener or agree with the default values.

 1. Diameter of pit.

 2. Diameter of widening.

 3. Height of side knife.

 4. Height of tank.

 1. Diameter of pit.
The minimum value is 10 cm. The maximum value is 40 cm (dimensions are limited structurally). Recommended values are 10, 20 and 30 cm. When choosing intermediate values, you will need a drilling rod to order.

 2. Diameter of widening.
The minimum diameter of the widening is equal to the diameter of the pit + 5 cm. The maximum diameter of the widening is equal to three diameters of the pit. Production outside of this range, in agreement with the customer.

 3. Height of side knife.
The minimum height is 5 cm (the size is limited structurally). The maximum height is 20 cm. Production of a knife with a height of more than 20 cm, in agreement with the customer.

 4. Height of tank.
The minimum height is 10 cm (the size is limited due to the need for centering the Widener). The maximum height is 50 cm. A container with a height / diameter ratio > 3 may cause difficulties with cleaning from the ground. Production of tanks with a height of more than 50 cm, in agreement with the customer.

 You can also specify the planned depth of the pit. This is an optional, reference size. If it is specified, in addition to the parameters of the Widener, the order will display:
 the total volume of the pit,
 the volume of the concreted part (the total volume of the pit, minus the volume drilled under the tank),
 volume of the cylindrical part,
 the volume of widening.
 The data is necessary to calculate the amount of concrete mix and the amount of work when creating the foundation.

The Widener parameters are selected on the order page in the corresponding section.

Justification of the use of the Widener and preliminary calculation of the scope of work

 The section turned out to be very extensive, but we tried to provide all the knowledge available to us on this issue. Since there is no such information anywhere else, and if it appears, it will most likely be copied from here.

 From the very beginning of our company's work, we received requests to make a Widener for the foundation. We were extremely skeptical about the idea of widening the bottom of the pit. We proceeded from the following: firstly, it is problematic to ram the expansion, which reduces the bearing capacity of the pile and, secondly, the expansion arch is unstable and prone to collapse (later, after obtaining real pits with widening, these concerns disappeared, as will be discussed below). The calculations themselves for the bearing capacity of the pile are given in the corresponding СНиП document posted on our resource in the technical information section in the Russian part of the site.

 Nevertheless, many years later, after persistent requests from the owners of our equipment, we returned to this topic. And for the technical justification to begin the development of a Widener, we decided to make calculations not on the bearing capacity of a separate pile, as we did before, but on the total amount of excavation work required to install the house on the foundation.

 The results were impressive. For calculations, we used the formula from the same СНиП document that is posted here. The calculation was extremely simplified and the incoming values were shifted towards reducing the bearing capacity of the soil and the pile itself. Thereby making this calculation applicable, as a preliminary, on almost the vast majority of soils, except in cases of permafrost or unstable soils (swamps, quicksand, etc.). Also, the calculation cannot be used for relief complications (slope, nearby ravine, etc.).


 Fd=(Yc⋅R⋅A)/10 – bearing capacity of the pile in tons

 where Yc - is the dimensionless coefficient of the working conditions of the pile.
0.8 was adopted, equal to the most difficult working conditions in dusty clay soils with a high degree of humidity and on loess soils.

 R - the value of the soil resistance under the lower end of the pile in kPa.

 А = π⋅(D/2)2 - the area of the support surface of the pile in m2. Where D - is the diameter of the support surface of the pile in m .

 The calculation is applicable for piles with a depth of 2.5-3 meters.

 The main parameter - is R, the resistance of the soil. If the pile is installed on clean, moist clay, then R = 250 kPa. But such a soil is very rare, the overwhelming part is loam with inclusions of hard rocks and R = 600 kPa should be taken for preliminary calculation.

 For comparison, an ordinary wooden house with an area of 36 sq. m. was chosen.
 The approximate weight of the house, taking into account the loads (snow + operational) and a margin factor of 1.3 - 80 tons;
 The specific density of concrete used to create the foundation is 2 t/m3

 And now the most important thing. Calculation of the required number of piles.

 To do this, divide the weight of the house by the bearing capacity of the pile and round it up to the nearest integer.

 The first case: a straight pile in a pit with a diameter of 30 cm (0.3 m) and a depth of 2.5 meters.
 Pile volume 0.177 m3, pile weight 0.354 t.
 A = π⋅(0.3/2)2 = 0,071 m2.
 Fd = ((0,8⋅600⋅0,071)/10)-0,354 = 3,054 t.
 Number of piles: 80/3,054 = 26,195 ≈ 27 piles.

 The second case: a pile with widening. A pit with a diameter of 20 cm (0.2 m), a widening of 60 cm (0.6 m) and a depth of 2.5 meters.
 Pile volume 0.213 m3, pile weight 0.426 t.
 A = π∙(0.6/2)2 = 0,283 m2.
 Fd = ((0,8⋅600⋅0,283)/10)-0,426 = 13,158 t.
 Number of piles: 80/13,158 = 6,080 ≈ 7 piles.

 The results obtained clearly speak in favor of the use of widening. Since it is possible to drill 7 holes with a diameter of 20 cm in a day. And to drill 27 holes with a diameter of 30 cm is a labor feat. And it will take a week. Even if we take into account that it is necessary to drill not 7 but 8 holes with widening, this is still work for one shift (while drilling and widening are carried out in parallel, two people drill and one does the widening). Two additional pits will be needed not because of the bearing capacity of the foundation, but so that the spans between the supports under the wall do not exceed 3 meters.

 Based on the new calculations, we decided to take up this topic. Initially, there was a desire not to go too deep into development, but simply to purchase existing devices from manufacturers and weld our standard RBI-5A adapter to them. But this idea died quickly. We purchased three devices from different manufacturers. They didn't find any more. We tried it out and it became clear that all this does not fit. To put it mildly, not the same dynamics at work. In addition, there was no possibility of scaling and flexible parameter changes. And the fundamental inability to work in a pit with a diameter of 100 mm, finally put an end to this idea.
 As a result, we had to develop this device from scratch. The plane-parallel scheme of the knives was taken as a basis, which allows flexibly changing the parameters of the product for specific tasks. Which corresponds to the policy of our company. The first released working samples work precisely with a minimum hole diameter of 100 mm. Which is technically the most difficult condition. And the devices themselves have no analogues in principle.

 After receiving the pits with widenings, work was carried out on ramming crushed stone at the bottom of such pits (in accordance with the СНиП). It turned out the following. The central hole has a tendency to ramming, and the support surface formed by the expander does not lend itself to ramming and driving rubble into it did not lead to noticeable results. Ramming was performed manually. A 15 kg pole with handles was used as a percussion instrument. Ramming was performed before the sound changed from quiet and deaf to a characteristic more sonorous one, obtained when hitting a relatively hard surface. The results of the tests are explained as follows. The central hole formed by the drill has a loose structure of the bottom and side walls. In addition, the remnants of loose soil that has fallen from the broadening area are inevitable. The surface formed by the Expander is smooth and not loosened and, upon impact, produces the same sound as the central hole after ramming. Naturally, with mechanized compaction of the soil, the efficiency would be higher. But in practice, pouring crushed stone into the central hole and a couple of minutes of work with the column gives a result that is indistinguishable from the mechanized method.

 By compacting the bottom of the experimental pits, doubts were removed on two key points, because of which we did not want to deal with this topic at all. This is the efficiency of compaction of the bottom of the pit and the collapse of the expansion arch. According to the results, we obtained: firstly, the density of the bottom of the pit with broadening is indistinguishable from the density of the bottom of a conventional pit, and, secondly, the arches of the pits did not collapse during ramming. This does not mean that the vaults will never collapse under any circumstances. But there is no particular tendency to destruction. Something, of course, is crumbling, but it will not interfere with concreting.

 In conclusion of the topic, creating a foundation with a manual drill, one important advantage of this method should be noted. Regardless of what kind of drilling is carried out, with or without widening.
 When creating the foundation, it is necessary to coordinate the actions between the excavation and the actual concreting. If it is decided that these works will be carried out by specialized organizations, then there is a critical problem. If earthworks and concreting are performed by the same organization, then this is good. But this is not available in many places, often only in large cities. Basically, these are different enterprises. One company is drilling and digging, and the second is a concrete plant that sends a concrete mixer truck. It is clearly unreasonable to call the mixer before the pits are ready, since any failure during excavation will lead to the fact that funds for a concrete machine will be wasted. When calling a concrete mixer truck after everything is ready for concreting, it is likely that by the arrival of the machine, part of the pits will partially collapse (and pits drilled in a mechanized way are more prone to collapse than pits drilled manually) and they will need to be corrected before starting concreting. To restore the collapsed pit, you will need a drill of the same diameter that the organization drilled, which in turn can become another acute problem. If you drill and mix concrete yourself, then such problems cannot arise in principle.

Scope of application

 The Widener (Underreamer) based on the RBI-5 drill is designed to create widenings in clay and sandy soils with inclusions of hard rocks up to five centimeters in diameter.

 The equipment can withstand a rotation force of up to 50 kgf * m (490 N * m) and a lifting force of up to 2 tons.

 Technical data, such as the weight and overall dimensions of the Widener or Underreamer, will vary widely. In this regard, specific values will be specified for four or five basic products. The first number in the designation is the initial diameter, the second number is the diameter of the widening (in centimeters).

 1. Widener 10-30.

 2. Widener 20-60.

 3. Widener 30-90.

 4. Widener 40-113.

 5. Widener 40-120.

 The approximate purpose of the Wideners, depending on the model.

 The main purpose of the basic model 10-30 is the creation of light foundations, with a bearing capacity of 3-4 tons per pile* and the installation of metal pillars with concrete filling of the base. The pillars can be installed at a shallow depth or even perform a surface installation. Drilling to a shallow depth with a 30 cm drill rod is, of course, more convenient, but it will not give that versatility when solving problems of installing pillars. For example, an expander can create arbitrary intermediate diameters and a ready-made central recess under the column is formed.

 Model 20-60. Most likely, it will be most in demand for foundation construction in private construction, with a bearing capacity of 14 - 15 tons per pile *.

 Модель 30-90. Creation of powerful foundations, with a bearing capacity of 32 - 35 tons per pile*.

 Модель 40-113 Creating particularly powerful foundations. The model is interesting because it creates a pile with a support surface of 1 sq. m. The bearing capacity of such a support is 52 - 54 t *. In addition, this equipment can be used to create large wells.

 Модель 40-120. Creating the largest possible widening on the basis of the RBI-5 drill. The bearing capacity of the support is 60-61 t*. In addition, this equipment can be used to create large wells.

 *The load-bearing capacity values correspond to the calculations and conditions given in the previous section.

Contacts for questions: configuration, application, delivery, etc.
tel. +7 (343‑88) 2‑27‑62
tel. +7‑967‑852‑42‑01
WhatsApp: +7‑992‑008‑72‑66
Viber: +7‑992‑008‑72‑66

Weight-overall characteristics of drilling equipment
(all dimensions in the figures are in millimeters)