System and method for sub-grade stabilization of railroad bed

Abstract

The invention is a system and method for repairing, improving, and stabilizing subgrade and subsoil/natural ground layers of a rail bed generally consisting of softer soils. One embodiment includes a method of installing subsurface inclusions and ballast fills comprising injected slurry mixtures of stabilizing material such as cement grout mixed with in situ soil. Another embodiment includes a system of installed ground inclusions and ballast fills. Another embodiment includes an integrated system of equipment for emplacing the system of inclusions and ballast fills.

Claims

1. A system for repairing a rail bed underlying a railroad having rails and cross ties, the system comprising: a rail mounted vehicle; a drill mast assembly mounted on the vehicle, the drill mast assembly having a drill mast frame that supports first and second drill masts spaced from one another, and a pair of drills and corresponding drill heads mounted to said drill mast assembly between said drill masts; a hydraulic lift secured to said drill mast assembly to raise and lower said drill mast assembly; a power source for powering the drills to selectively penetrate the rail bed; a pump; a grout source wherein the pump operates to transfer the grout through a transfer line to the drill mast assembly; and wherein the drill heads inject the grout into the rail bed.

2. The system, as claimed in claim 1, further comprising: a cement silo for storing grout material; and a transfer line connected between the silo and pump enabling transfer of grout material from the silo to the pump.

3. The system, as claimed in claim 2, further comprising: a rail trailer mounted on the rails and supporting the cement silo.

4. The system, as claimed in claim 3, further comprising: an engine mounted on the rail trailer; and drive tracks mounted on the rail tracks and communicating with the engine to propel the trailer.

5. The system, as claimed in claim 1, wherein: the vehicle has wheels enabling the vehicle to be driven off and driven onto the rails.

6. The system, as claimed in claim 5, wherein: the vehicle has rail guides removably secured to the vehicle to maintain alignment of the wheels on the rail track.

7. The system, as claimed in claim 1, wherein: the drill heads are selectively and controllably lowered to drill holes in the rail bed and are subsequently lifted to inject grout to form inclusions in the drilled holes.

8. The system, as claimed in claim 7, wherein: the vehicle is operated to incrementally advanced to position the drills to emplace a plurality of inclusions that are spaced from one another along a length of the rail bed.

9. A method for stabilizing subgrade and subsoil ground layers of a railroad bed underlying a railroad having rails and cross ties, the method comprising: providing a rail mounted vehicle, a drill mast mounted on the vehicle, the drill mast having a drill mast frame that supports first and second drill masts, the first and second drill masts supporting a pair of drills and corresponding drill heads; determining a location on the railroad where the subgrade or subsoil have failed causing destabilization of the ballast upon which the rails and cross ties lie; rotating the drill mast including the drill mast frame and first and second drill masts from a first stowed position to a second vertical operating position for drilling; positioning the drills over the location to a first position; drilling first holes by the drills into the subgrade and/or the subsoil; withdrawing the drills and injecting a grout mix by the drill heads as the drills are withdrawn to form corresponding first inclusions in the first drilled holes; moving the vehicle and repositioning the drills over the location to a second position spaced from the first position; drilling second holes by the drills; and withdrawing the drills and injecting the grout mix by the drill heads as the drills are withdrawn to form corresponding second inclusions in the second drilled holes.

10. The method, as claimed in claim 9, further comprising: injecting the grout mix in a ballast pocket to fill the ballast pocket forming ballast fill that communicates with at least one inclusion.

11. The method, as claimed in claim 9, further comprising: varying a rate of injection of the grout mix through the drills to selectively form the inclusions considering a volume of the drilled holes.

12. The method, as claimed in claim 10, further comprising: varying a rate of injection of the grout mix through the drills to selectively form the ballast fill considering a volume of the ballast pocket.

13. The method, as claimed in claim 9, further comprising: determining a scope of the failed subgrade and/or subsoil; determining a number of inclusions required to repair the subgrade and/or subsoil; predetermining an array of inclusions to emplace considering the number of inclusions required; and sequentially emplacing the array of inclusions including a plurality of the inclusions that are spaced along a length of the railroad and spaced laterally from one another.

14. The method, as claimed in claim 13, wherein: the array comprises a preselected number of rows of inclusions and a preselected lateral spacing of the inclusions in the rows.

15. The method, as claimed in claim 14, wherein: the rows include at least two rows of inclusions extending along a length of the railroad.

16. The method, as claimed in claim 14, wherein: the lateral spacing of the inclusions includes at least one of a pair of laterally aligned inclusions located on interior sides of corresponding rail tracks.

17. The method, as claimed in claim 14, wherein: the lateral spacing of the inclusions includes at least one of a pair of laterally aligned inclusions located on exterior sides of corresponding rail tracks.

18. The method, as claimed in claim 14, wherein: the lateral spacing of the inclusions includes at least three laterally aligned inclusions.

19. The method, as claimed in claim 9, further comprising: selectively changing a lateral spacing of the drills on the drill mast to match a desired lateral spacing of inclusions to be formed.

20. The method, as claimed in claim 9, wherein: the vehicle and drill mast remain mounted on the railroad during emplacement of the inclusions.

21. A system for repairing a rail bed underlying a railroad having rails and cross ties, the system comprising: a rail mounted vehicle; a drill mast assembly mounted on the vehicle, the drill mast assembly having a pair of drills and corresponding drill heads mounted to said drill mast assembly between said drill masts; a hydraulic lift secured to said drill mast assembly to raise and lower said drill mast assembly; a power source for powering the drills to selectively penetrate the rail bed; a pump; a grout source wherein the pump operates to transfer the grout through a transfer line to the drill mast assembly; and wherein the drill heads inject the grout into the rail bed.

22. A method for stabilizing subgrade and subsoil ground layers of a railroad bed underlying a railroad having rails and cross ties, the method comprising: providing a rail mounted vehicle, a drill mast mounted on the vehicle, the drill mast supporting a pair of drills and corresponding drill heads; determining a location on the railroad where the subgrade or subsoil have failed causing destabilization of the ballast upon which the rails and cross ties lie; rotating the drill mast including the pair of drills and drill heads, by use of a hydraulic lift secured to the drill mast, from a first stowed position to a second vertical operating position for drilling; positioning the drills over the location to a first position; drilling first holes by the drills into the subgrade and/or the subsoil; withdrawing the drills and injecting a grout mix by the drill heads as the drills are withdrawn to form corresponding first inclusions in the first drilled holes; moving the vehicle and repositioning the drills over the location to a second position spaced from the first position; drilling second holes by the drills; and withdrawing the drills and injecting the grout mix by the drill heads as the drills are withdrawn to form corresponding second inclusions in the second drilled holes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view of the rail mounted system of the invention including a depiction of the major components or pieces of equipment making up the system;

(2) FIG. 2 is an enlarged perspective view showing components of the equipment system including a drilling rig, jet grout mixture and pump, and cement silo;

(3) FIG. 3 is another perspective view of the equipment shown in FIG. 2 and further illustrating a drill mast of the drill rig as it is rotated for deployment from a stowed position;

(4) FIG. 4 is another perspective view of the equipment shown in FIG. 2, and further illustrating the drill mast in a fully deployed position;

(5) FIG. 5 is a greatly enlarged perspective view showing the drilling heads penetrating the ballast and subgrade;

(6) FIG. 6 is another greatly enlarged perspective view showing the drilling heads further penetrating the subgrade beyond a ballast pocket;

(7) FIG. 7 is another greatly enlarged perspective view showing the drilling heads being retracted from their fully inserted position and injecting a grout slurry mixture in the drilled holes and mixing the grout slurry with in-situ soils;

(8) FIG. 8 is another greatly enlarged perspective view showing the drilling heads being further retracted to inject additional grout in the boreholes and being lifted or retracted to an elevation within a ballast pocket;

(9) FIG. 9 is another greatly enlarged perspective view showing the drilling heads moved to a subsequent inclusion emplacement and in which the ballast pocket was previously filled with the desired grout material;

(10) FIG. 10 is yet another greatly enlarged perspective view showing a plurality of inclusions emplaced in an array;

(11) FIG. 11 is a cross-sectional elevation view of a rail bed showing a failed ballast layer caused by shifting or settling of the underlying subgrade and/or subsoil;

(12) FIG. 12 is a cross-sectional elevation view as shown in FIG. 11 in which the failed ballast layer is repaired by two rows of ground inclusions and ballast fills to fill corresponding ballast pockets underlying the ballast layer

(13) FIG. 13 is another cross-sectional elevation view as shown in FIG. 11 in which the failed ballast layer is repaired by four rows of ground inclusions and ballast fills to fill corresponding ballast pockets underlying the ballast layer;

(14) FIG. 14 is a partial cross-sectional side elevation view of a railroad bridge abutment that incorporates ground inclusions;

(15) FIG. 15 is a plan view showing one particular configuration or array of emplaced inclusions, more specifically, two rows of inclusions and one pair of inner adjacent inclusions;

(16) FIG. 16 is a plan view showing another configuration or array of emplaced inclusions, more specifically, four rows of inclusions located between every third cross tie;

(17) FIG. 17 is a plan view showing another configuration or array of emplaced inclusions, more specifically, four rows of inclusions located between every other cross tie; and

(18) FIG. 18 is a plan view showing another configuration or array of emplaced inclusions, more specifically, four rows of inclusions located between each cross tie.

DETAILED DESCRIPTION

(19) FIG. 1 is a perspective view of the rail mounted system of the invention including a depiction of major components or pieces of equipment making up a system 10 mounted on a railroad with tracks T. The major components of the equipment comprise three elements mounted on a trailer 12 illustrated as an engine 14, a cement silo 18, and a combined jet grout mixer and a pump unit 22. The other major component includes a hi-rail truck 24 and a drill mast assembly mounted to the truck 24.

(20) The trailer 12 has drive tracks 13 that are propelled by the engine 14. A cab 15 is provided for an operator to control the engine 14. The cement silo 18 holds a desired quantity of cement grout mix in preparation for installation of the ground inclusions and ballast fills. An inlet port 20 allows for charging the cement silo with the grout materials. The jet grout mixer and pump unit 22 are employed to mix the grout materials received from the cement silo 18 and to convey the mixed grout to a drill mast assembly 30. In one configuration, the pump unit draws grout material from the cement silo 18 and introduces the material to a downstream mixer that mixes the grout with water. An outlet of the mixer communicates with the drill mast assembly to convey the mixed grout for injection. One or more grout material conveying lines (not shown) are provided between the cement silo 18 and the jet grout mixer and pump unit 22. Another group of conveying lines (not shown) carries the mixed grout material to the drill mast assembly with the drills 44.

(21) The hi-rail truck 24 is also rail mounted and is connected to the trailer 12. The hi-rail truck incorporates one or more power takeoff shafts (PTOs) that can be used to power a hydraulic pump (not shown) mounted to the truck to provide hydraulic power to operate the drill mast assembly 30. The bed of the truck 24 may also have an electric generator 26 loaded thereon, such as a diesel generator, which is capable of providing power for the overall equipment system 10, job site lighting, or other electrical power needs that may arise at a job site.

(22) The truck 24 is further equipped with railway guide wheels 29 that enable the truck 24 to be transported along a rail line. The wheels 28 of the truck 24 preferably rest upon and are centered along the upper surfaces of the tracks T. The truck may be separated from a rail line in which the railway guide wheels 29 are either retracted or removed enabling the truck 24 to be driven to another location as necessary. A plurality of water tanks 36 are mounted to the vehicle and provide a water supply for mixing of the grout during batching. Accordingly, grout can be mixed immediately with a supply of water that is rail mounted with the other equipment. There is no need to search for an onsite water source.

(23) Referring also to FIGS. 2-4, these figures show further details of the equipment including a drilling rig comprising the drill mast assembly 30. In FIG. 2, the drill mast assembly 30 is shown in a stowed position, FIG. 3 shows the drill mast assembly 30 in a partially raised position, and FIG. 4 shows the drill mast assembly in a fully raised or deployed position. The drill mast assembly 30 includes a drill mast frame 32 which supports two drill masts 34. The drill mast frame 32 is rotatably attached to the rail truck by a support frame 38. A pair of hydraulic lift cylinders 40 is operated to raise and lower the drill mast assembly. One end of each of the lift cylinders is secured to a bed of the rail truck 24, and the opposite ends are secured to the drill mast frame 32. The drill mast assembly may be precisely moved to the fully deployed position so that the drill masts 34 introduce the drill heads 46 of the drills 44 at a desired inclination angle. In most cases, the drills 44 are oriented substantially vertical, but in some cases, the drills may require positioning at a slight angle.

(24) FIG. 5 is a greatly enlarged perspective view showing the drilling heads 46 penetrating the ballast B and subgrade SG in a downward descent. More specifically, the drill mast 34 is operated to hydraulically power the drills 44 to penetrate the subgrade SG a desired depth. In this example, the drill heads 46 are oriented on the inside edges of the tracks T to penetrate the ground between respective cross ties T. FIG. 5 also shows a ballast pocket BP in the subgrade.

(25) FIG. 6 is another greatly enlarged perspective view showing the drilling heads further penetrating the subgrade beyond the ballast pocket BP to a desired depth to commence grout injection through the bores of the drills 44 and out through nozzles in the drilling heads 46. As the drills penetrate, they mix the soil in the drilled holes. The drills may have a desired exterior flute or projection design so that some amount of the soil material is evacuated making space for the injected grout while some soil material remains within the hole to mix with the grout. A desired concentration mix of soil and grout can be predetermined at the jobsite based on the type of soil present. One objective however is to not generate a significant amount of waste soil that requires removal. Accordingly, a preferred procedure is one in which a minimum amount of waste soil is generated from the drilled holes, and this minimum amount will not materially contaminate the ballast fill over the drilled holes.

(26) FIG. 7 is another greatly enlarged perspective view showing the drilling heads 46 being retracted from their fully inserted position and injecting a grout mixture in the drilled holes to form a soil-grout mixture inclusion or subsurface column 60. The shape of the inclusions is generally cylindrical. More specifically, the grout mixture may be defined as cement grout that is mixed with the existing soil to form a cementitious slurry. The cement grout is injected through the drill heads 46 at a pressure, therefore this technique may be also described as a hydrodynamic mix-in-place technique that produces a soil-cement column or rigid inclusion that improves the soil both in bearing strength and shear strength. The diameter of the installed inclusions is dependent on actual in-situ soil conditions. A minimum diameter for the inclusions may be approximately 6 inches based on injection pressures and the drill head diameters. As mentioned, injection pressures may be varied to increase or decrease the rate of flow of cement grout which can be adjusted to achieve a desired soil-cement mixture ratio, as well as to most efficiently fill drilled holes and ballast pockets.

(27) FIG. 8 is another greatly enlarged perspective view showing the drilling heads 46 being further retracted to inject additional grout material in the drilled holes and lifted to an elevation within the ballast pocket BP. At this point, the lifting of the drills is paused so that the ballast pocket can be filled. The pump unit 22 may have a pressure sensing capability to adjust a volumetric flow of the grout material based on pressure associated with the injection. Increased delivery line pressure will indicate when a drilled hole is adequately filled as well as when a ballast pocket is adequately filled.

(28) FIG. 9 is yet another greatly enlarged perspective view showing the drilling heads 46 moved to a subsequent inclusion emplacement and showing the ballast pocket BP as filled forming a subsurface ballast fill 70. The truck 24 is operated to propel the system a desired incremental distance along the tracks T for emplacement of the subsequent inclusion emplacements.

(29) FIG. 10 is yet another greatly enlarged perspective view showing a plurality of inclusions 60 emplaced in an array comprising two rows or sets of inclusions 60 and a ballast fill 70. A desired number and pattern or array of inclusions and ballast fills may be emplaced by incremental movement of the truck along the rails. Because the equipment remains rail mounted, and because drilling can occur directly from the drill mast aligned over the rail tracks and cross ties, there is no additional effort required to reposition the equipment or to move raw materials to the job site. Accordingly, the system and method of the invention is fully mobile and greatly reduces manpower and overall costs associated with traditional railroad repair and maintenance.

(30) The drills 44 may be laterally displaced on the drill rig to achieve different lateral spacing of emplaced inclusions. Specifically, the drills may each be independently shifted in a lateral direction so that inclusions can be emplaced at any desired lateral spacing on the rail bed.

(31) FIG. 11 is a cross-sectional elevation view of a rail bed showing a failed ballast layer B caused by shifting or settling of the underlying subgrade SG and/or subsoil. A rail vehicle V is illustrated over the rail bed. The ballast layer B forms an upper layer or crown of the rail bed as shown. Two laterally spaced ballast pockets BP underlie the ballast layer B. In addition to the ballast pockets, another gap exists between the cross ties T and the upper portion of the ballast layer B shown as gap G. This gap G along with the ballast pockets BP result in shifting and settling of the cross ties and rails. The displaced locations of the cross ties and rails along with inadequate support to withstand the dynamic loading of a passing train results in a compounded rail bed failure that may create a significant potential danger to rail operations. A worst case scenario is one in which a train can derail as caused by excessive displacement of the tracks T and cross ties C. FIG. 11 also shows a shear failure line 90 that is intended to represent an example of how the ballast B can slip and settle between adjacent ballast sections 92 and 94. In this example, the shear failure causes ballast section 92 to sink and shift resulting in the formation of gap G.

(32) FIG. 12 is a cross-sectional elevation view as shown in FIG. 11 in which the failed ballast layer B is repaired by two rows of ground inclusions 60 and two distinct ballast fills 70 underlying the ballast layer B.

(33) FIG. 13 is another cross-sectional elevation view as shown in FIG. 11 in which the failed ballast layer B is repaired by four rows of ground inclusions 60 and two distinct ballast fills 70 underlying the ballast layer B.

(34) FIGS. 11-13 represent only a few examples of inclusion configuration or arrays. It should be understood that each inclusion 60 may be selectively emplaced with a pre-selected depth and circumference. While one uniform size for the drill heads 46 are shown, the drill mast assembly 30 may be fitted with drill heads of varying diameters capable of drilling holes to different corresponding diameters.

(35) FIG. 14 is a side elevation and partial cross-sectional view of a railroad bridge abutment that incorporates ground inclusions. More specifically, FIG. 14 shows an exemplary rail bridge construction 100 with abutment walls 102 and a bridge span supported by a truss assembly 104. A rail line 106 traverses the bridge span in which the adjacent bridge abutments may require additional support. The abutment in FIG. 14 is intended to illustrate one which has been constructed with backfill material that is bounded on one side by an abutment wall 102 and the abutment backfill tapers to a decreasing depth as the abutment extends away from the bridge span. The abutment may include wing walls (not shown) or other lateral containing features for the backfill material making up the abutment. FIG. 14 further shows one of the abutments in cross-section with an array of inclusions 60 installed to repair subsurface defects in the bridge abutment. As shown, the inclusions 60 increase in depth as the inclusions approach one end of the bridge span. The inclusions 60 stiffen the abutment to reduce dynamic loading on the bridge itself. The inclusions 60 also reduce the inherent stiffness differential between the rail track embankment and the bridge structure which therefore reduces bridge vibration and displacement under live loading conditions. Stiffening of the bridge abutment may therefore contribute to an extended service life for both the bridge and the abutment.

(36) FIG. 15 is a plan view showing one particular configuration or array of emplaced inclusions, The rail bed area illustrated is designated with a centerline (CL) 88 and four areas that define locations on both lateral sides of the center line 88. A first area may be defined as extending along line 80 that lies on one exterior lateral side of a track T; a second area may be defined as an area extending along line 82 that lies on the opposing exterior lateral side of the other track T, a third area may be defined as an area extending along line 84 that lies on one interior lateral side of a track T; and a fourth area may be defined as an area extending along line 86 that lies on the opposing interior lateral side of the other track T. The particular configuration or array of inclusions illustrated in FIG. 15 is one row of inclusions centered on line 80, another row of inclusions centered on line 82, one inclusion centered on line 84, and one inclusion centered on line 86. The inclusions on lines 80 and 82 are spaced along every third cross tie C.

(37) FIG. 16 is a plan view showing another configuration or array of emplaced inclusions. More specifically, this figure shows four rows of inclusions along lines 80, 82, 84, and 86 in which each inclusion is located in a gap between every second cross tie C. Each of the four rows is laterally aligned such that there are four inclusions 60 across a lateral line that can be drawn between the four inclusions.

(38) FIG. 17 is a plan view showing yet another configuration or array of emplaced inclusions. More specifically, this figure shows four rows of inclusions along lines 80, 82, 84, and 86 in which each inclusion is located in gap between very other cross tie. Each of the four rows is laterally aligned such that there are four inclusions 60 across a drawn lateral line.

(39) FIG. 18 is a plan view showing yet another configuration or array of emplaced inclusions. More specifically, this figure shows four rows of inclusions along lines 80, 82, 84, and 86 in which each inclusion is located in a gap between each adjacent cross ties. Each of the four rows is laterally aligned such that there are four inclusions 60 across a drawn lateral line.

(40) The array of inclusions in FIGS. 15-18 is exemplary and other patterns of inclusions 60 can be employed within an array. As mentioned, each array may have inclusions placed at different depths and each inclusion can be a different effective diameter. The illustrated arrays are shown as being symmetrical with regard to longitudinal and lateral spacing of the inclusions; however, an array can also be non-symmetrical by the concentration of one or more inclusions at an area that may require greater repair and support.

(41) According to one of the methods of the invention, it includes the method for determining a design for stabilizing a rail bed comprising: identifying a rail bed with one or more failed subsurface areas; determining an area of the failed areas; determining a depth of the failed areas under a surface of the rail bed; calculating a required bearing capacity of the rail bed; determining a differential between an actual bearing capacity considering the failed subsurface areas and the required bearing capacity; determining an optimum subgrade stiffness modulus; calculating a number of subsurface inclusions required to stabilize the rail bed including a spacing between the subsurface inclusions, depths of emplacement, and sizes of the inclusions; automatically generating a design layout with depicted subsurface inclusions and spacing. This method may further include stabilizing the rail bed by emplacement of inclusions according to the design layout by rail mounted equipment including a high rail mounted drilling rig. The design layout produced may be facilitated by a computer processor and associated programmable instructions in which basic input parameters are entered and a visual display is provided for the design layout. For example, input parameters may include the measured failed areas and the existing and required bearing capacity. The optimum or target subgrade stiffness modulus may be determined as another input parameter. The design layout is generated with one or more options as to the number, spacing, and size of inclusions that satisfy design parameters including the required bearing capacity and subgrade stiffness modulus. Soil conditions may also serve as another input parameter. The programmable instructions are able to access a database with a number of design layouts with predetermined effects as to how a particular design layout may contribute to adequately stabilizing the rail bed. In other words, the database may comprise a number of proposed design layouts that achieve adequate bearing capacity and subgrade stiffness considering the type of soil present and an identification of the size and location of failed subsurface areas. By providing a pre-existing suite of design options, the method of determining a design for use in the field is simplified in an automated context.

(42) There are many advantages to the system and methods of the invention. The integrated system that is rail mounted with a drilling capability provides an economical and efficient way to significantly improve the stability of failing subgrade and subsoil conditions. Maintenance costs are reduced over time because emplaced inclusions and ballast fills provide long-term soil stabilization. The minimally invasive repairs that can be conducted do not require any separate stabilization efforts with respect to the subgrade/subsoil and the ballast layers. Resurfacing of the most upper ballast layer may be required, but this is a relatively low-cost task with minimal effort required.

(43) Because of the rail mounted equipment that does not require offloading or any equipment to be positioned on the ground adjacent to the railroad, the system and method is also advantageous within environmentally sensitive areas in which expensive and protracted permit processes can be avoided. In most circumstances, a railroad has an easement or right-of-way across land, but the railroad does not own the land around or on the rail bed. Therefore, permits may normally be required to access environmentally sensitive lands where equipment can be offloaded and operated. The rail mounted equipment of the system completely eliminates off-rail traffic at a job site.