Method of planting rod-shaped member in foundation

The method of affixing a bolt in a hole in foundations formed of materials such as concrete, stone or rock, wood and the like which includes inserting a bolt in said hole, filling the space surrounding said bolt with a plurality of balls, pouring a liquid curable resin into the hole to fill the interstices between the balls and then curing the resin and the resulting structure.

This invention relates to a method of planting a rodshaped member in a 
foundation such as a rock or concrete base and the resulting structure. 
This method and structure are especially useful for plantation of an 
anchor bolt which has to bear a large tensile force, for example, in 
building construction. 
In case of planting an anchor bolt in a foundation in accordance with the 
prior art, it has been the general practice to bore a hole in the 
foundation, put the bolt therein and then fill the remaining space in the 
hole with a filling material such as cement or mortar. However, such prior 
art techniques have not been advantageous in that it is necessary to bore 
a very deep hole in order to achieve the allowable strength required under 
the Industrial Standard and that it takes a significantly long time for 
the filling material to harden and exhibit sufficient strength. In 
addition to the laborous and time-consuming work, it has been almost 
impossible to correct the position of the bolt after fillint the hole with 
the filling material. 
Accordingly, an object of this invention is to provide a novel and improved 
method and structure for planting a rod-shaped member, such as anchor 
bolt, in a foundation, such as rock or concrete, which can greatly improve 
facilitation and efficiency of work and reduce the term thereof, by 
removing the abovementioned disadvantages. 
According to this invention, the method of planting a rod-shaped member in 
a foundation comprises the steps of forming a hole with an inner diameter 
greater than the outer diameter of said member in the foundation, 
inserting an end of said member in said hole, filling the remaining space 
in the hole with a plurality of ball-like members having substantially 
uniform diameters, adding a liquid synthetic resin material and, then, 
heardening the synthetic resin material. 
Other objects and features of this invention will be described in more 
detail hereinunder with reference to the accompanying drawings and in 
conjunction with some examples.

EXAMPLE 1 
Referring to FIG. 1, a cylindrical hole 1 having an inner diameter of 42 
millimeters and a depth of 250 millimeters was formed in a base rock 2 
using a boring machine. After cleaning the interior of the hole with a 
vacuum cleaner, a threaded bolt 3 having an outer diameter of 16 
millimeters and a length of 330 millimeters was inserted in the hole 1. 
Alumina ceramic balls 4 each having a diameter of about 5 millimeters, the 
balls being available commercially for use in a ball-mill pot, were put in 
the hole 1 to about one third of the depth of the hole to cause the bolt 3 
to become selfsupporting, so that position correction of the bolt could be 
effected easily. After correcting the position of the bolt 3, a 
composition consisting of epoxy resin of bisphenol A 
(2,2-bix(4'-hydroxyphenol)propane) type as main component and 
m-xylylenediamine as hardener was poured in the hole 1 to the same level 
as the balls 4. Then, similar balls 4 were added in the hole 1 to the 
surface of the base rock 2 and the same composition was poured to the same 
level as shown. Although a part of the balls were omitted from the drawing 
for specification, it should be noted that they are completely packed in 
the space of the hole 1. Thereafter, a final correction of the bolt 
position was executed and the structure was left as it was for about 72 
hours at room temperature to harden the resin composition. 
A tension test was carried out by clutching the bolt 3 to pull it out, and 
resulted in breakage of the bolt at 7,500 killograms. 
When the same test was carried out using conventional mortar as the filling 
material, the bolt was easily pulled out without breakage of either the 
bolt or the hardened mortar. In order to obtain the same result as this 
example, it was necessary not only to make the depth of the hole more than 
three times in order to afford the necessary frictional resistance of the 
bolt but it was also necessary to greatly increase the diameter of the 
hole to facilitate pouring the mortar having much lower fluidity. 
EXAMPLE 2 
Referring to FIG. 2, a square hole 11 was previously formed in a concrete 
foundation 12. The hole had a depth of 350 millimeters and a square 
cross-section of 100.times.100 millimeters. An anchor bolt 13 having an 
outer diameter of 25 millimeters and a length of 450 millimeters was 
planted in the hole 11 with the filling material of 10 millimeter glass 
balls 14 and a resin composition similar to that of Example 1. The 
plantation procedure was substantially similar to that of Example 1. After 
the resin composition was hardened for about 72 hours, a motor base (not 
shown) was fixed by the bolts 13 on the foundation and rotation of the 
motor was started immediately. Trouble has not been encountered and the 
installation has already been functioning for three months. 
EXAMPLE 3 
Referring to FIG. 3(A), cylindrical holes 21 were formed in a concrete 
foundation 22. While the diameters of the holes 21 were maintained at 42 
millimeters, depths of 200, 300 and 400 millimeters were used. Steel bolts 
23A each having a diameter of 16 millimeters and a tensile strength of 
about 45 killograms per square millimeter and being threaded over the 
whole length was planted in each hole with filling materials of 6 
millimeter alumina ceramic balls 24 and an epoxy resin composition used in 
the above examples. The plantation process was carried out in the same 
manner as in Example 1. 
Another group of specimens was prepared similarly to the above except that 
each steel bolt 23B was not threaded over the lower portion to be embeded 
in the hole as shown in FIG. 3(B). 
Six specimens were prepared for each specific condition and tensile 
strengths were measured after 72 hours for the specimens 1, 2 and 3 and 
after 168 hours for the specimens 4, 5 and 6. The result of the 
measurements was summarized in the following table. In the table, the 
symbols A and B correspond respectively to the bolts 23A and 23B in FIG. 
3. 
TABLE 
__________________________________________________________________________ 
Depth 
200 mm 300 mm 400 mm 
Spec. 
A B A B A B 
__________________________________________________________________________ 
1 11,800(a) 
7,100(a) 
13,400(a) 
12,800(b) 
16,000(c) 
17,500(c) 
2 11,500(a) 
6,900(a) 
13,800(b) 
12,100(b) 
15,700(c) 
17,800(c) 
3 11,500(a) 
7,000(a) 
13,500(b) 
12,500(b) 
15,500(c) 
16,900(c) 
4 12,000(b) 
7,200(a) 
13,500(b) 
13,000(b) 
15,800(c) 
19,800(c) 
5 11,800(b) 
7,000(a) 
14,000(c) 
12,500(b) 
16,000(c) 
19,500(c) 
6 11,500(a) 
6,900(a) 
14,000(b) 
12,500(b) 
15,000(c) 
20,300(c) 
__________________________________________________________________________ 
The numerical values in the table represent breaking loads in killograms 
and the symbols (a), (b) an (c) represent the breaking conditions or 
states, wherein (a) corresponds to peeling off between the foundation and 
filling material, (b) corresponds to breakage of concrete and (c) 
corresponds to breakage of bolt. 
The above result shows very small dispersion of the measured values of 
three specimens and ensures reliability of the method. It also shows that 
a sufficient strength can be obtained above 400 millimeters in depth and 
above 72 hours curing time in this example. It has been confirmed that 
depth more than 1,000 millimeters and curing time more than one week are 
required for obtaining the similar result and that the dispersion of the 
measured values is much greater and lower reliability is anticipated, when 
conventional mortar is used as the filling material. 
Gravel, sand and crushed stone were tested as substitutes for the ceramic 
balls in the resin composition. However, the results showed much 
inferiority as compared with the ceramic balls in both mean value and 
dispersion of the measured tensile strengths. Moreover, it was found that 
the use of these filling materials made it difficult to move the bolt for 
position correction and also interfered with the expelling of air bubbles. 
Glass balls and steel balls substituted for the ceramic balls showed a 
little inferior results. This is believed to be due to smoothness of the 
ball surfaces. Among many kinds of balls which were tested, alumina 
ceramic balls which were non-glazed and commercially available for use in 
a ball mill were found to be preferable. 
In the above examples, bisphenol A epoxy resin having viscosity of about 
185 centipoises at 20.degree. C. was used together with hardener. However, 
it should be self-evident to those skilled in the art that other moldable 
resins such as polyester resin, phenol-formaldehide resin, melamine resin, 
polyvinyl chloride resin and polyvinylidene resin, which exhibit minimum 
volumetric shrinkage, are also useful. 
It has been found that the tensile strength tends to increase with 
reduction of ball size, that is, with increase in packing density of the 
balls. However, the packing density is limited in practice because it 
becomes difficult to drive the viscous resin composition into small 
cavities between the balls. Repeated tests have showed that the gap 
between the bolt and the hole wall should preferably be at least 1.5 times 
the ball diameter. This suggests that the improved strength obtained in 
accordance with the method of this invention has come from frictional 
resistance between the balls and, therefore, that it is desired to 
establish a hexagonal close-packed structure throughout the balls in order 
to obtain maximum strength. For completeness of this structure, it is 
desired that the balls be as uniform in diameter as possible and that each 
ball be ideally spherical. Compressive strength of the ball should be 
large enough to overcome the tensile load, that is, at least greater than 
that of the foundation material. 
Although the method of this invention was described above in conjunction 
with certain embodiments, it should be noted that various modifications 
and changes can be made without departing from the scope of this 
invention. For example, this method can be applied also to other 
foundations such as wood and stone in addition to the aforementioned 
concrete and base rock.