CA2944709C

CA2944709C - Structural support

Info

Publication number: CA2944709C
Application number: CA2944709A
Authority: CA
Inventors: Casey Moroschan
Original assignee: Poly Mor Canada Inc
Current assignee: Poly Mor Canada Inc
Priority date: 2016-10-07
Filing date: 2016-10-07
Publication date: 2024-01-09
Anticipated expiration: 2036-10-07
Also published as: CA2944709A1

Abstract

A method of forming a structural support in earth below a ground surface is disclosed. A water-resistant confinement unit is placed in the earth below the ground surface, the confinement unit having a first end oriented towards the ground surface, a second end opposite the first end, and the first end having an opening. Granular material is released into the confinement unit through the opening to at least partially fill the confinement unit with granular material. Expandable polymeric resin is injected into the confinement unit to at least partially fill the confinement unit to compress earth around the confinement unit.

Description

STRUCTURAL SUPPORT
TECHNICAL FIELD
[0001] Supports for ground supported structures.
BACKGROUND

[0002] A traditional method of densifying base soils to provide support for ground supported structures, called pressure grouting or permeation grouting, involves forcing a high density cementitious material under high pressure into the base soils with a view to increase the bearing capacity of the soils. However, in the case of weak soils there is no controlling of the amount of grout that is required and as such, extreme amounts of grout can be pressure pumped into the soils with limited or no positive results. This is especially true in the case of highly saturated soils. Methods are known for injecting polymeric foam into bags underground for supporting weak soils, for example as disclosed in US
published application no. 20150016897 published January 15, 2015.
SUMMARY

[0003] A method of imparting strength to earth or soil is disclosed. A
confinement unit is placed in the earth below a ground surface, the confinement unit having a first end oriented towards the ground surface, a second end opposite the first end, and the first end having an opening. Granular material is released into the confinement unit through the opening to at least partially fill the confinement unit with granular material. Expandable polymeric resin is injected into the confinement unit to at least partially fill the confinement unit to compress earth around the confinement unit.

[0004] In various embodiments, there may be any of the following: the confinement unit is filed with granular material until full; the method further comprises injecting gas to at least partially fill the confinement unit prior to releasing granular material into the confinement unit; injecting expandable polymeric resin comprises injecting the expandable polymeric resin initially at the second end of the confinement unit; placing a confinement unit in the earth comprises putting the confinement unit onto the end of a tube and pushing the tube into the earth; the method further comprises drilling a hole in the earth prior to placing the confinement unit in the earth; placing a confinement unit in the earth comprises placing the confinement unit at the bottom of the hole.

[0005] A confinement unit is also disclosed for use in imparting strength to earth below a ground surface. The confinement unit comprises at least an opening, a first end and a second end opposed the first end. The confinement unit is located in earth under the ground surface and at least partially filled with granular material and expandable polymeric resin to compress the earth around the confinement unit. In various embodiments, the confinement unit may include the following: the opening further comprises a backflow prevention valve to prevent material contained within the confinement unit from passing out of the confinement unit when the opening is unobstructed, the confinement unit is water-resistant, the confinement unit is waterproof, and the granular material is gravel.
BRIEF DESCRIPTION OF THE FIGURES

[0006] Embodiments will now be described with reference to the figures, in which like reference characters denote like elements, by way of example, and in which:

[0007] Fig. Ito Fig. 4 are side elevation views, in section and not to scale, of earth below a ground surface and illustrating a process forming a confinement unit packed with gravel and resin in earth below a ground surface.

[0008] Fig. 5 is a flow diagram that illustrates a method of imparting strength to earth below a ground surface.
DETAILED DESCRIPTION

[0009] Immaterial modifications may be made to the embodiments described here without departing from what is covered by the claims.

[0010] This document relates to the construction of in-situ expandable vertical/horizontal support member(s) in weak base soils as a means of densifying the weak base soils for supporting and under-pinning structures on these soils. For example, these methods and apparatuses may carry out the densification of foundation soils support systems for buildings, walks, bridge approaches, concrete or asphalt paved roads, rail beds, and any other structure requiring a base support system or requiring enhancement or strengthening of the existing soil-based support system.

[0011] The present disclosure is directed to providing a controlled method of densifying soils at depth to increase bearing capacity of the weak soils as an alternative to pressure grouting and to direct injection of expanding polymer resins into weak base soils.
Weak alluvial soils and silts replete with peat, hog fuel, and other weak sediments that may be highly saturated and demonstrative of Standard Penetration Test N-values of 5 or lower are examples of soils that this disclosure relates to.

[0012] In many types of weak soils, such as weak alluvial soils, silts, clay, peat, hog fuel, wood chips, and water saturated soils for example, the inherent strength of the earth below the ground surface is limited. Soils of these types are known to have caused hazardous situations such as standing derailments of trains, and the cracking of foundations of various structures. In order to stabilize these types of soils, and prevent such incidents from occurring, the earth below the ground surface must be strengthened.

[0013] Fig. 1 to Fig. 4 show apparatus used in an embodiment of a method of forming a structural support in earth 10 below a ground surface 12. In Fig. 5, a method of forming a structural support in earth below a ground surface is outlined. In stage 100 of Fig.
5, a water-resistant or waterproof confinement unit or bag 14 is placed in the earth 10 under the ground surface 12, the confinement unit 14 having a first end 16 oriented towards the ground surface 12, a second end 18 opposite the first end 16, and the first end 16 having an opening 20. Injector tubes 26 are placed in the confinement unit before, during or after installation of the confinement unit in the ground, so that at some stage there are injector tubes 26 in the confinement unit as illustrated in Fig. 2.

[0014] In stage 102, granular material 22 is released or dropped into the confinement unit through the opening 20 to at least partially fill the confinement unit 14 with granular material 22 such as gravel. Filling the confinement unit 14 may include dropping gravel in the confinement unit 14 until no more gravel is able to fit in the confinement unit.

[0015] In stage 104, expandable polymeric resin 24 is injected into the confinement unit 14 through the opening 20 to at least partially fill the confinement unit 14 to compress earth 10 around the confinement unit 14. The expandable polymeric resin 24 reacts to form foam which expand and fill confinement unit 14, encapsulating the granular material 22 and compressing and densifying the earth 10 around it as it expands. By densifying and strengthening the weak adjacent soils, the weight bearing capacity of the ground surface 12 is increased, and overlying structures may be more easily stabilized and built on top. The gravel and resin packed confinement unit forms a structural support within the earth that is capable of supporting a structure above the ground surface.

[0016] Confinement unit 14 may be made of non-expandable material, for example thick polymer material. The material may resist the expansion of the confinement unit itself, thus compressing the inside and outside of the confinement unit while maintaining structural integrity. In some embodiments, the confinement unit is made of resilient material. The confinement unit 14 may be placed in the hole 28 before or with one or more injections tubes 26. Gravel 22 may be placed in the confinement unit 14 through opening 20 or through the injection tubes 26 if they are large enough. The one or more injection tubes 26 may be used to inject expandable polymeric resin 24 into the confinement unit 14 after gravel 22 is placed in the confinement unit 14. The gravel 22 may be placed in the confinement unit 14 by dropping the gravel from a tube, chute or shovel (not shown). The confinement unit 14 acts to contain the gravel 22 and polymeric resin from escaping into the earth 10 around the confinement unit 14.

[0017] The one or more injection tubes 26 may be located at different depths within the confinement unit 14. Each injection tube 26 may be used for injection of resin and gas and may provide access for granular material.

[0018] Hole 28 may be created by any suitable means such as drilling with metal devices or with a hydrovac unit. The drilling device (not shown) may be removed upon completion of the hole and prior to placement of confinement unit 14, and tube 26. In other embodiments, hole 28 may be drilled in the earth using a hollow drill stem connected to a sacrificial drill bit. In some embodiments, injection tube 26, along with the confinement unit 14 is placed in the hollow drill stem under the ground surface 12. In some weak soils, the hollow drill stem may be required to prevent the drilled hole from collapsing prior to placement of the confinement unit. In some embodiments, the confinement unit may be driven through the weak earth without requiring a hole.

[0019] Prior to releasing gravel into confinement unit 14, gas, for example compressed air, may be injected to at least partially fill the first confinement unit 14. Gravel may be released into the confinement unit 14 multiple times. Between each addition of granular material, further injections of air may be made to expand the confinement unit 14.
As the confinement unit 14 is inflated, the granular material accumulates near the second end of the confinement unit 14. Re-inflation of the confinement unit by injection of gas may be required depending on the composition of the earth 10. For example, where re-inflation may be required where earth 10 are very weak, such as when the earth is super-saturated and acts like water. The confinement unit may be expanded in-situ as much as possible using compressed air to allow as easy as possible filling of each confinement unit with granular material and expandable polymeric resin.

[0020] Referring to Fig. 2, releasing of granular material 22 may be through inserting the granular material through the one or more injection tubes 26. Granular material 22, gas and resin 24 may each be provided through the same injection tube 26. Gravity may act on the granular material to bring the granular material to the second end 18 of the confinement unit 14. The amount of granular material 22 required may be determined by comparing the volume of the confinement unit 14 to the volume of granular material 22 accepted by the confinement unit. Injection of the expandable polymeric resin may proceed first with the injection end of tube 26 near the second end 18 of confinement unit 14. Spaces in between the granular material 22 may be filled by the resin as the resin moves within the confinement unit and the confinement unit may expand as the resin is injected. The granular material may be enveloped by the resin 24, and the resin 24 may bind the granular material together. The water-resistance or waterproof nature of the confinement unit may allow the resin to bind with the granular material with limited or no water to interfere with the binding. Once confinement unit 14 has begun to accumulate resin 24, the injection tube or tubes 26 may be gradually drawn up towards opening 20 or each injection tube 26 may be left at the same level in the confinement unit 14 during injection of polymeric resin, then left embedded in the gravel and polymer composite. The resin may be hydro-insensitive polyurethane for example.

[0021] Prior to injecting expandable polymeric resin into the confinement unit 14, gas may be injected to further expand the confinement unit to facilitate injection of the resin.
In some embodiments, the expandable polymeric resin is added as a liquid and fills the confinement unit through the expansion of the polymeric resin, the balloon effect on the confinement units compacting and compressing the base soils surrounding the confinement unit. By filling the confinement unit 14 with air prior to injection, the expandable polymeric resin is allowed to freely flow into confinement unit 14 between the granular material 22 and properly fill, yet be confined by, the dimensions of confinement unit 14 upon expansion.

[0022] Referring to Fig. 2, after gravel 22 is placed in the confinement unit 14 and polymeric resin 24 is injected into the confinement unit 14, the resulting structure may be used as a structural support 54 for a ground surface 12 or a building placed on the ground surface 12. The support 54 comprises confinement unit 14 located in earth 10 under the ground surface 12 and at least partially filled with granular material 22 and expandable polymeric resin 24 to compress the earth 10 around the confinement unit 14.

[0023] In some of the embodiments of methods disclosed herein, the earth comprises at least one of weak alluvial soils, silts, clay, peat, hog fuel, wood chips, and water saturated soils. It should be understood that each method disclosed herein can incorporate all the characteristics of the other methods.

[0024] In the embodiments of the methods disclosed herein, the expandable polymeric resin may be expanding polymeric resin that comprises a high density, closed cell expanding two component polyurethane foam system. The resin may be hydro-insensitive. In some embodiments, the polymeric resin is a high density, two-part, closed cell expanding polymeric resin system, such as a polyurethane system which is injected into the confinement unit or array of confinement units. The particular foam system used may be tailored to meet specific design applications relating to tensile strength, compressive strength, shear strength, flexural strength and other structural characteristics to meet the specific design applications of the controlled foam densification system. It is also possible to use other expandable substances having similar properties.

[0025] The expansion rate of the freely blown polymeric resin system is known as is the approximate relationship of the expanding polymeric resin system under confinement in a weak soils condition and hence the amount of resin can be pre-estimated to minimize resin usage and maximize soils densification around the confinement unit or array of confinement units.

[0026] The shape and size of containment units, constructed of natural or synthetic fibers for example, will be determined depending upon the soils conditions.
The weaker the soil's condition, the larger the containment unit may be in both width and depth. The containment bags will typically not be symmetrical in shape to enhance the stability of the filled bag in the weak soils as well as enhance any "friction" effect the containment unit may have. The containment units may be designed to meet specific soils needs, for example using a containment unit in a specifically weak soil strata that has been designed to more so compact the weak soil as compared to the soils above and below the weak strata.

[0027] The use of a bag to confirm the polymeric resin is mainly beneficial for densification of weak and very weak base soils with N-values being no larger than 5. Any base soil condition with N-values greater than 5 can be directly injected with an expanding polyurethane to densify these base soils. Direct injection into weak and very weak base soils proves ineffective and uneconomical as tremendous amounts of expanding polymer resin can be injected into these weak soils and the tendency for the material is to set up in vertical wing patterns that really do not compact and compress the base soils to increase density and load bearing capacity. Accordingly, a confinement unit is required to be placed in and through the weak soils strata and then filled with an expanding polymer resin to effectively compact the base soils laterally and provide support vertically as well. There is a direct relationship between the strength of the base soils being treated and the lateral compressibility of these weak soils.

[0028] It has been determined that the design of any confinement unit has limitation in terms of the diameter of the unit. The maximum diameter to effectively produce a contiguous column of solid polyurethane is in the order of 2' ¨ 2.25'. A
larger diameter confinement units would only be applicable in very, very weak soils which are determined to be quite compressible. Another mitigating element against larger diameter confinement units is the polyurethane foam system employed because of the way the system actually expands ¨
le: larger volume areas are not as effectively filled especially when injected into rather lengthy confinement units. Further, because the polyurethane system tends to follow the route of least resistance it will tend to move vertically instead of laterally thus mitigating the effect of laterally compacting the weak base soils.

[0029] It may be difficult to effectively fill a long confinement unit by simply employing one injection port. To ensure proper and effective fill of a confinement unit the confinement should be compartmentalized, for example, at 7' ¨ 8' intervals with injectors located within each compartment. In some embodiments, the compartments are defined by the location of the injectors within the gravel. The gravel resists movement of the polymeric resin from a specific nozzle or injector tube. The polymeric resin then stops moving when it encounters the confinement unit or polymeric resin from another nozzle or injection tube. In another embodiment, the confinement unit may be compartmentalized with one or more dividers 30, shown in Fig. 3A. The divider 30 may be formed by material such as tape, paper or other fragile membranous material that extends across the confinement unit.
The divider may be placed during filling of the confinement unit with gravel. After a set amount of gravel is placed in the confinement unit, the divider is inserted, then additional gravel added.
The divider used to make the compartments may be be very weak so when the expanding resin hits that area it will actually tear the tape and completely fill the confinement unit. The diameter of the confinement unit will be determined by the compressability of the base soil.
The weaker the base soil and more compressable it is the larger the diameter of the confinement unit.

[0030] Different polyurethane systems have different coefficients of expansion and thus depending upon the density of the polyurethane system the amount of material to be injected into each compartment of the confinement unit can be predetermined.
The denser the polyurethane system the less expansion is realized upon injection and thus more material is required to effectively fill the confinement unit. Additionally, since the polyurethane foam is confined it will densify itself to a degree as a result of this confinement ¨ ie: it compact and compresses itself in confinement thereby requiring more material to effectively fill the confinement unit. This densification of the foam results in a stronger column of foam within the confinement unit as well as requiring lower density foam systems to effect the same job.
Depending upon the volume of the confinement unit; the compressibility of the soils being treated and the foam system being used determines the amount of material that will be injected into each compartment to provide an effective fill of the confinement unit.

[0031] A challenge in the densification of weak soils using a confinement unit is what grid pattern needs to be employed to effectively densify the weak soils.
For structures that are lineal in nature such as rail beds, building foundations and the like a tighter grid pattern and may be required depending upon the weakness of the base soils and other factors.
Weak liquefiable soils can also be treated using confinement units and a much tighter staggered grid pattern is required to give assurance that the weak typically saturated silts and sands will not liquefy in the event of seismic activity.

[0032] In the claims, the word "comprising" is used in its inclusive sense and does not exclude other elements being present. The indefinite article "a" before a claim feature does not exclude more than one of the feature being present. Each one of the individual features described here may be used in one or more embodiments and is not, by virtue only of being described here, to be construed as essential to all embodiments as defined by the claims.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of providing a structural support in earth, the method comprising:
placing a confinement unit in the earth below a ground surface, the confinement unit having a first end oriented towards the ground surface, a second end opposite the first end, and the first end having an opening, the confinement unit being water impermeable;
releasing granular material into the confinement unit through the opening to at least partially fill the confinement unit with granular material; and injecting expandable polymeric resin into the confinement unit through the opening to at least partially fill the confinement unit to compress earth around the confinement unit.

2. The method of claim 1 in which the confinement unit is filled with the granular material until full.

3. The method of any one of claims 1-2 further comprising injecting gas to at least partially fill the confinement unit prior to releasing the granular material into the confinement unit.

4. The method of any one of claims 1 ¨ 3 in which injecting expandable polymeric resin comprises injecting the expandable polymeric resin initially at the second end of the confinement i n't.

5. A structural support in earth, comprising a confinement unit having at least an opening, a first end and a second end opposed the first end; the confinement unit being water impermeable; and the confinement unit being located in earth below a ground surface and at least partially filled with granular material and expandable polymeric resin to compress the earth around the confinement unit.

Date recue/Date received 2023-04-19