GB2119100A - A method of, and an apparatus for surveying a region of soil to which a stabilising chemical has been added - Google Patents

Abstract

In a soil grouting agent injection region surveying method for use in surveying the grouting agent injection region in a soil stabilisation process at least two electrodes are arranged in the area to be surveyed and the resistance of the soil therebetween measured. In the arrangement shown rods (Q,R) carrying electrodes (1 to 8) are positioned in the soil spaced from a chemical grouting opening carrying an electrode P. A potential is applied between the electrodes and changes in the resistance determined to obtain the extent of stabilisation of the soil. A chemical grouting pipe assembly including a swivel joint may be provided with an electrode. Alternatively two earth augers can carry the electrodes. <IMAGE>

Description

SPECIFICATION A method of, and an apparatus for surveying a region of soil to which a stabilising chemical has been added The present invention relates to a method and apparatus for surveying a region of soil into which a grouting agent, e.g., a chemical (hereinafter simply referred to as a chemical) is injected in the course of a soil stabilisation process.

A known method of soil stabilisation in the field of civii engineering works comprises injecting a solidifying chemical into the objective soil area to solidify there, and thereby solidify and stabilise the soil or make it impervious to water.

The types of soils requiring stabilisation include ordinary soil layers, rock fissures, dislocated broken zones or any combinations thereof, and the effect of the grouting is dependent on the properties of the soil strata in many cases.

In other words, when the injected stabilising chemical leaves the grouting pipe, it penetrates into the strata in accordance with the applied pressure and it tends to penetrate towards or into that region of the strata having the minimum resistance to the grouting, e.g., the soil layer boundaries or the gravel stratum or soft silt stratum having a large coefficient of permeability.

Thus, there is a danger of a phenomenon arising in which the whole injected chemical is not necessarily solidified within the intended region of the objective soil, even if the gelling time of the chemical is adjusted.

In performing this type of chemical feeding operation, it is necessary to observe the presence of leakage of the chemical so as to prevent the chemical from escaping from a predetermined chemical feeding region around the chemical grouting hole and flowing into any wells, ponds, reservoirs, streams or the like in the vicinity of the job site thereby contaminating the underground or surface water. This observation has been accomplished by boring and installing observation wells on the outer side of a chemical feeding region, the observation wells having a radius of about 10m from the centre of the chemical grouting hole. A quality test is then conducted on the water in the observation wells at three different stages comprising before, during and after the injection of the chemical into the chemical grouting hole.The data from the quality test can confirm leakage of the chemical to the outside of the predetermined chemical feeding or injection region.

With the above described method, however, if a situation arises where the pH value of the water in the observation well exceeds a predetermined reference value, due to the actual escape of the chemical to the outside of the chemical feeding region as a result of the test performed at the injection stage of the three water quality test stages, it is necessary to immediately stop the chemical feeding operation on the site where the chemical grouting hole is located. Actually, the quality test of the water in the observation well during the chemical injection requires a considerable time delay until the chemical which hasescaped to the outside of the feeding region has infiltrated into the water in the observation well because of the distance of 1 Om between the grouting hole and the observation well.Consequently, since the chemical feeding operation has progressed considerably by the time that the pH value of the water at the place of the observation well is found to exceed the reference value, the feeding operation must be stopped at that time and a grouting hole must be bored again at a different place and the operation must be started anew from the initial stage, thus causing a heavy loss in terms of time, equipment and labour.

With a view to overcoming these deficiencies, methods have recently been proposed in which, for example, an instantaneous solidifying chemical is first injected to ensure a stabilised soil region and then the ordinary chemical feeding operation is effected, and generally it has been difficult to quantitatively confirm the grouted region by such method.

To determine the solidified region, various methods have been proposed including digging up the soil as a matter of principle as well as the use of measurements of the coefficients or permeability, the penetration test, the measurement by means of a radioisotope, the seismic prospecting, etc.

While the digging up of soil, the use of a radioisotope and the seismic prospecting have been used in the case of large-scale stabilisation works, the use of these methods are not iniversal. Under these circumstances, while the method of determining the cut-off effect on the basis of the measured coefficent of permeability has not been most widely used, this method has not always been universally used and it has not developed to the state of being convenient to use.

In view of these circumstances, it has been the practice with the known soil stabilisation methods, utilizing the injection of chemicals, to complete the work upon the injection of a predetermined amount of a chemical without being able to confirm the actual condition attained upon completion of the stabilisation work.

Accordingly, it is an object of the present invention to overcome at last some of the deficiencies in the prior art.

According to one aspect of the present invention, a method of surveying a region of soil to which a chemical has been added in order to stabilise the soil comprises providing at least two electrodes in the soil, the electrodes being spaced from each other, and passing a current between the electrodes through the soil and measuring the electrical resistance between the electrodes and using the measured electrical resistance to provide an indication of the condition of the region. Preferably, the change in the electrical resistance between the electrodes is measured. Advantageously the measured electrical resistance is compared with an electrical resistance measured on a sample of the soil which has had a chemical added to it in order to stabilise the soil.

The method may comprise comparing the measured electrical resistances to provide a prediction or estimation of the strength of the soil after the stabilisation or solidification of the soil has been completed.

Preferably, the method includes at least one monitoring bore with at least one electrode, the monitoring bore being spaced from another bore with at least one electrode through which the chemical is added, comprising measuring the electrical resistance between the electrodes. Advantageously a plurality of monitoring bores are included and the method comprises measuring the electrical resistance between the electrodes of the monitoring bores and the electrode or electrodes of the bore through which the chemical is added.

Preferably, the method comprises adjusting the flow rate of the chemical or the amount of chemical which is added to the soil in response to the measured electrical resistance.

According to a further aspect of the present invention, a soil grouting agent injection region surveying method for surveying a grouting agent injection region in a soil stabilisation process comprises the steps of: arranging at least two electrodes in an area to be surveyed; supplying a current to said electrodes from power supply means; and measuring an amount of change of an electrical resistance between said electrodes.

According to another aspect of the present invention a strength measuring method comprises the steps of: arranging at least one pair of electrodes in positions on both sides of a grouting agent injection region in a soil stabilisation process; measuring an electrical resistance value of an unsolidified grouting agent between said electrodes; and comparing said measured value with a preliminary measured electrical resistance value of a sample having the similar conditions to said grouting agent and thereby predicting an after solidification strength of said grouting agent in the unsolidified condition thereof.

According to a further aspect of the present invention a chemical grouting pipe assembly comprises a swivel joint including a terminal electrically connected to an electrode located on an outer wall of a grouting pipe rod, the electrode being rotatable relative to the terminal, the grouting pipe rod including at least one inner, co-axially extending rod which defines an inner passage and an outer passage, the cable extending through one of the passages, the other of the passages being arranged to carry the chemical. Preferably, the present invention includes a grouting pipe assembly when used in a method of surveying a region of soil to which a chemical has been added in order to stabilise the soil.

According to a further aspect of the present invention the chemical grouting pipe apparatus for use in soil improvement comprises: a swivel having an electric circuit closed between one terminal arranged ahead of said swivel and a cable connector positioned at a central portion of the lower end of said swivel through a slide brush and cable; a grouting pipe rod including a cable conduit having another cable connector at each end thereof and disposed centrally in a concentric multi pipe; and an electrode equipped with grouting pipe rod including another cable conduit having still another cable connector at each end thereof and disposed centrally in another concentric multi pipe, and an electrode disposed on an outer wall thereof and connected to a lead wire extended from said other cable connector; said swivel, said grouting pipe rod and said electrode equipped grouting pipe rod being suitably connected to each other.

It has been found that the measured values of the electrical resistance exhibit a quantitive and marked behaviour in the presence of a gel in the soil.

The present invention therefore provides a soil grouting agent injection region surveying method for surveying a grouting chemical injection region in a soil stabilisation process which comprises arranging electrodes in an area to be surveyed, the electrodes receiving a current generated from a power source and measuring the amount of change of an electric resistance therebetween, and a work control method-and a measuring apparatus which utilize the said surveying method.

The invention may be carried into practice in various ways by a number of embodiments will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a sectional view of a chemical grouting triple pipe swivel.

Figure 2 is a schematic diagram showing a chemical being injected into a hole bored by means of augers.

Figure 3 shows a test gel buried in sand with (a) showing a plan view and (b) a central sectional side view.

Figures 4 to 6 are graphs showing how the electrical resistance value varies with distance under certain conditions.

Figure 7 is a schematic diagram showing the positions of a chemical grouting pipe and observation pipes.

Figure 8 is a schematic diagram showing the manner in which a chemical is injected by a high pressure injection method.

Figure 9 is a schematic diagram showing a chemical being injected through a boring chemical grouting pipe.

Figure 70 is a graph.

The term "chemical" is used throughout this specification to mean any one of those chemicals which may be used in soil stabilisation including, for example, organic chemicals such as lignin, urea, acrylic acid and acrylamide chemicals as well as water glass, cement milk, etc.

The area to be measured includes an area covering ideally a region of a uniform radius from a grouting pipe driven into the soil where the chemical injected into the pipe is expected to penetrate or an area covering non-uniform coefficients of permeability in the soil if the same have already been determined by test borings.

The term "electrode" refers to one which can emit or receive a current and which, if it is placed in a chemical grouting pipe, should preferably be separated from the grouting pipe by an insulator such as plastic and protected by a case which is reiiable in strength. Regarding the arrangement of the electrodes in the chemical grouting pipe, if the single electrode is used, the electrode may be buried in the vicinity of the grouting pipe end, e.g., in a portion of the bit. If a plurality of electrodes are used, they may be buried in the wail of the grouting pipe at suitable intervals.

Where such electrodes are arranged on an observation pipe, as many electrodes as possible should preferably be provided so as to effect a pluralistic observation with a high degree of accuracy.

Each of the electrodes arranged on the chemical grouting pipe and the observation pipes may be wired to the lead wire inside the pipe and then connected to a transmitter and a receiver on the ground.

Figure 1 shows a triple pipe swivel joint, the swivel joint including a plurality of terminals 1 which are arranged on the head of the swivel joint and are insulated from the surroundings by an insulator 18. Each terminal 1 is connected through a slide brush 4 to a rotary terminal 3 disposed on the outer side of an electrode spindle 2 which is sealably held within the swivel pipe portion for rotation about its shaft. Lead wires are brought out from inside the rotary terminals 3 and are connected to suitable connecting terminals, e.g., a cable connector 6 in the lower region of the swivel joint, through a cable conduit 5 disposed centrally in the swivel shaft.

A middle tube 7 is provided to form a first fluid passage 9 between it and a surrounding swivel sheath tube 8, and the top of the tube 7 forms a closed passage above a fluid inlet 10.

A coaxial inner tube extends through the middle tube 7 to form a second fluid passage 12 between it and the middle tube 7, and the top of the tube 11 forms a closed passage above a second fluid inlet 13.

The middle tube 7 and the inner tube 11 are rotatably sealably supported by means of O-rings 14, bail bearings 15, U-cups and an oil seal 17.

The lower ends of the swivel sheath tube 8, the middle tube 7 and the inner tube 11 are formed into a plug or socket for connection to a grouting pipe rod (a triple pipe in this embodiment).

The grouting pipe rod includes a cable having a cable connector at each end and it has a triple pipe construction which provides a first and second fluid passage corresponding to those in the swivel joint.

The cable connecting portion including the cable connector 6 may be provided with some allowance in length so as to facilitate the connection of another cable during the connecting operation of the grouting pipe rod.

If the above-described swivel joint and grouting pipe rod are used, an external power source for example may be connected to the terminals 1 provided on the swivel head so that the application of a suitable voltage (e.g., about 6 to 12 V) causes the flow of a current in the soil from the grouting pipe electrodes located along the cable conduits. As a result, by arranging other electrodes to catch the current at different places, it is possible to easily determine the feed condition of the chemical in accordance with the rate of decrease in the electrical resistance which varies in dependence with the extent (or the layer thickness) of the chemical injection region.

Another embodiment of the invention will now be described with reference to the soil cement pile forming apparatus shown in Figure 2. Earth augers 23 and 23' of the duplex type are inserted into an objective soil 21 so that a cement milk 26 is injected from the tips or vanes 25 and 25' of auger stems 24 and 24'. The soil particles are pulverised and the cement milk 26 and soil particles 22 are stirred and mixed together. The auger stems 24 and 24' are respectively provided with electrodes 27,28, 29 and 27', 28', 29' which are arranged at equal intervals and insulated from the associated stems themselves, and a lead wire 30 or 30' extends from each electrode, through which the stem 24 or 24', to above the ground.The lad wires 30 and 30' leading from the electrodes are connected so that a power supply 31 and a resistance gauge 32 are arranged between the pairs electrodes 27 and 27', 28 and 28' and 29 and 29', respectively, each pair being arranged in the same vertical positions in relation to the auger stems 24 and 24'.

Priorto mixing the concrete A by digging up soil particles by the earth augers 23 and 23' and supplying the cement milk 26, a sample of the freshly mixed concrete A is prepared on the ground and the necessary data of electrical resistance values in the freshly mixed concrete is obtained from the sample. This sample data is obtained by for example adding and mising a mixture of predetermined amounts of cement and water with the pulverised soil particles 22 and measuring the electrical resistance values in the freshly mixed concrete between electrodes spaced apart by the same distance Was are the earth auger stems 24 and 24'.

To obtain a concrete having the same or similar conditions as the sample, the proportions of raw materials for soil cement to be placed in the actual pile formation are determined preliminarily by calculation, that is, the amount of cement milk to be supplied, on the basis of the amounts of cement and water, is calculated in accordance with, for example, the amount ofpulverised soil calculated on the basis of the diameter of the earth auger 23 and 23' and the depth.

After the desired amount of soil cement has been placed and mixed thoroughly in the soil 21 shown in Figure 2, a current is supplied to the electrodes 27, 28, 29 and 27', 28', 29' provided on the auger stems 24 and 24' and the electrical resistance values of the fresh soil cement A between the electrodes 27 and 27', 28 and 28' and 29 and 29', in the same vertical positions respectively, are measured by the resistance guages 32.

Experiments conducted have shown that the electrical resistance value of a mixture comprising 20009 of sand and 4009 of water was 77Q when measured by two electrodes spaced apart by a distance of 1 Ocm, whereas the measured value was 260Q when 1009 of cement was added to the same mixture and mixed for one minute and the measured value was 200Q when the later mixture was mixed for five minutes.

It has also been shown that the addition of 2000g of sand, 400g of water and 200g of cement and the mixing of these for one minute resulted in an electrical resistance value of 150Q between the electrodes, and the mixing of these for five minutes resulted in an electrical resistance value of 130Q. It will be seen that the addition of cement to a mixture of sand and water decreases the electrical resistance value between the electrodes, and that a more thorough mixing of the cement mortar homogenises the ingredients and decreases the electrical resistance value further.

It will be appreciated that the earth augers are not intended to be limited to the duplex type.

The use of the above-described apparatus has the advantage not only of positively determining whether the work being executed is progressing satisfactorily but also enabling an incomplete work to be detected and corrected by injecting additional chemical. Furthermore, the direction of escape of the chemical can be detected and the contamination of the drinking water, rivers or the like can be prevented.

The following specific examples describe in greater detail the construction and effects of the invention.

Example 1 As shown in (a) and (b) of Figure 3, sand 42 having a moisture content of 10.5% was placed in a plastic box 41 and a sand gel 43 having a diameter of 1 Ocm and a length of 20cm was buried in the sand 42. Electrodes were arranged at equal intervals in the diametrical direction of the gel body 43 and each electrode was connected to a Kohlrausch bridge type resistance gauge (the BF-62A manufactured by Shimazu Manufactory). The resulting behaviour of resistance values was measured as shown in Figure 4.

In Figure 4, a curve A shows the resistance values obtained in the case where one electrode was positioned in the central portion of the gel and the other electrode was moved away from the central portion (as shown by the arrows A in Figure 3), and a curve B shows the case where one electrode was fixed (at point B in (a) of Figure 3) and the other electrode was moved in the direction of the arrow passing through the central portion of the gel so as to move away from the point B.

As will be seen clearly from Figure 4, the gel has a very small resistance value and a marked change in electrical resistance value takes place at the boundries between the gel body and the sand. It has been confirmed that this phenomenon similarly takes place even if the sand is replaced with a clay or a pulverised granite soil. It has also been found that the depth of the measurement has practically no effect on the measuring current flowing through the gel body.

Example 2 A water glass-sand test gel of three-layer construction was formed into a cylindrical shape of 15cm in diameter and about 30cm in length with the water glass concentration of the central portion (up to a radius of about 2.5cm), the middle portion (up to a radius of about 5cm) and the outer peripheral portion being 38.6%, 23.9% and 11.2%, respectively. This test gel was buired in sand having a moisture content of 10.3% and the variations of the resistance values corresponding to the different distances in the diametrical directions from the central portion of the gel body were measured and are shown in the following table. The resulting behaviour is shown by the solid line in Figure 5.

There was practically no change in electric resistance among the individual layers ofthethree-layered water glass gel body.

Distance Left Hand Right Hand (cm) (X102Q) (X102Q) 2.5 0.13 0.13 3.5 0.20 0.21 5.0 0.23 0.26 6.0 0.35 0.36 7.5 0.45 0.47 8.5 13.2 12.8 10.5 19.8 21.0 15.0 30.0 32.0 Example 3 The same procedure as used in the Example 2 was repeated except that the similar gel body was used in the example 2 was buried in pulverised granite soil having a moisture content of 17.3% and the results obtained are shown in the following table. The resulting resistance value behaviour is shown by the broken line in Figure 5.

Distance Left Hand Right Hand (cm) (X1 0252) (X102Q) 2.5 0.17 0.17 3.5 0.35 0.29 5.0 0.48 0.4 6.0 0.77 0.62 7.5 1.0 0.75 8.5 16.9 17.2 10.0 24.0 19.8 15.0 31.0 34.0 It will be seen from these results that by measuring the electrical resistance values at the work site, it is possible to obtain in practice such a behaviour as shown in Figure 6 and thereby clearly grasp the extent of the gel body.

In the Figure, it will be seen that a curve A shows a soil undergoing no treatment and a curve B shows the presence of a gel body at a certain point by the behaviour indicated by the broken line. A curve C shows the resistance values measured starting at the central portion of the gel body and this curve allows the confirmation of the limited extent.

Example 4 As shown in Figure 7, Checking devices Q and R were inserted into locations which were spaced apart from a chemical grouting opening P by different distances, and a voltage was applied between the P and Q and the P and R, respectively, and the electrical resistance between the terminals was measured and is shown in the following table. Note that the distance P-Q was 1 m and the distance P-R was 75cm. The deepest depth of the rods from the ground was 4.5m and the measuring points 1, 2, 3,4 and 5,6,7,8 of the checking devices Q and R, respectively, were arranged at equal intervals of 50cm from the deepest points. The objective soil consisted of the bank extending from the ground surface to85cm, a clay silt down to 310cm and medium sand down to 450cm.

As will be clearly seen from the table, the limits of the chemical injection region can be grasped extremely clearly.

Electric Resistance (OHM) Measured section P-1 P-2 P-3 P-4 P-5 P-6 P-7 P-8 1-5 2-6 3-7 4-8 Injected quantity 0 225 250 270 250 230 245 260 370 76 124 174 270 20 49 72 90 77 54 76 89 143 86 141 173 200 40 48 71 97 75 50 74 89 120 86 142 174 258 60 45 69 98 74 49 68 88 90 84 160 138 116 180 44 69 103 76 45 70 85 85 83 132 188 156 200 43 70 103 78 38 8.6 63 83 77 71 164 156 240 43 68 112 80 37 7.5 65 72 74 73 172 148 260 43 68 94 14.6 40 8.2 72 68 79 73 151 81 280 43 9.7 20.5 13.8 39 8.3 67 70 78 14 73 79 300 43 9.9 8.9 11.8 37 8.2 67 68 77 13.6 69 76 320 43 8.5 8.3 9.6 37 7.7 60 61 45 12.1 67 77 340 9.8 7.5 7.6 9.7 38 7.9 68 70 43 11.2 69 70 Figure 8 is a schematic diagram showing another embodiment of the invention.A hole is formed in the objective soil by means of a boring grouting pipe having a bit and employing an air jet or high pressure water, and the boring operation is stopped upon reaching the desired depth. Then, a chemical is issued under a high pressure of about 50 to 1500 Kg/m2 from a lateral nozzle of the boring grouting pipe and the soil particles, in the direction of movement of the high pressure fluid, are stirred while the chemical penetrates and solidifies them. The boring grouting pipeis lifted or lowered with or without being rated and a stabilized region of an extent dependent on the injection pressure and/or the permeability coefficient of the soil particles is formed. In this case, by inserting measuring electrodes E into predetermined positions to measure the electric resistances during the execution of the work, it is possible to execute the work satisfactorily.

Example 5 After the installation of detecting pipes, a chemical grouting hole was bored at the desired location. In this case, while it was usual practice to use a boring pipe having a chemical grouting function, the one used further included an electrical signal transmitting terminal or sensor at a suitable position on its forward end and the resistance value R0 of the soil was measured continuously or intermittently as the depth ofthe bored hole was increased and the measured values were stored in a computer.

After completion of the boring operation, an instantaneously solidifying or slow solidifying chemical was used properly depending on the structure pf the soil and the chemical grouting pipe was continuously or intermittently while injecting the chemical. In this case, the electric signals were generated continuously from the terminals provided at the chemical grouting pipe end so that the signal quantity R, varying from time to time, was received by the sensors on the detecting pipe installed in the surrounding region and sent continuously to the computer.

More specifically, as shown in Figure 9, with detecting pipes II and Ill arranged in the symmetrical positions with respect to a grouting pipe I at a distance of 50cm therefrom, the grouting pipe I was lifted in steps of 50cm such that the initial injection quatity of O - 160C was supplied at the position i of the grouting pipe outlet, the next 160 - 320t at the position ii, the next 320 - 460t at the position iii, the next 480 - 640t at the position iv and so on (the position of the sensor on the grouting pipe 1 was of course raised from a to din steps) and the values of the chemical injection quantity and the electrical resistance were obtained.

The behaviour of the resistance value was successively fed into the computer which was computed and displayed the values of the continuously inputted R on the basis of a resistance value R100 corresponding to the formation of a 100% of gel body in the soil. By representing the values on a display, recording paper or the like in the form of a longitudinal sectional view of the both sides of the chemical grouting pipe, it was possible to show clearly the penetration of the chemical, as shown in Figure 10. Thus, there is a remarkable effect in that by changing the detecting pipes, it is possible to grasp and confirm the condition of the chemical injection layer by layer and thus it is possible to assume the responsibility for the result of the work.

In Figure 10, the hatched area indicated at G represents an ideal injection region and the broken line area is a graphic representation of the injection region resulting from the actual growing. The dot-and-dash line shows the sections of the gelatized portions in the same direction which were obtained as the result of the actually digging up the region.

Claims (14)

1. A method of surveying a region of soil to which a chemical has been added in order to stabalise the soil comprising providing at least two electrodes in the soil, the electrodes being spaced from each other, and passing a current between the electrodes through the soil and measuring the electrical resistance between the electrodes and using the measured electrical resistance to provide an indication of the condition of the region.

2. A method as claimed in Claim 1 in which the change in the electrical resistance between the electrodes is measured.

3. A method as claimed in Claim 1 or Claim 2 in which the measured electrical resistance is compared with an electrical resistance measured on a sample of the soil which has had a chemical added to it in order to stabilise the soil.

4. A method as claimed in Claim 3 in which comparing the measured electrical resistances provides a prediction or estimation of the strength of the soil after the stabilisation or solidification of the soil has been completed.

5. A method as claimed in any preceding claims including at least one monitoring bore with at least one electrode, the monitoring bore being spaced from another bore with at last one electrode through which the chemical is added comprising measuring the electrical resistance between the electrodes.

A method as claimed in Claim 5 including a plurality of monitoring bores comprising measuring the electrical resistance between the electrodes of the monitoring bores and the electrode or electrodes of the bore through which the chemical is added.

7. A method as claimed in any preceding claim comprising adjusting the flow rate of the chemical or the amount of chemical which is added to the soil in response to the measured electrical resistance.

8. A soil grouting agent injection region in a soil stabilisation process comprising the steps of: arranging at least two electrodes in an area to be surveyed; supplying a current to said electrodes from power supply means; and measuring an amount of change of an electric resistance between said electrodes.

9. A strength measuring method comprising the steps of: arranging at least one pair of electrodes in positions on both sides of a grouting agent injection region in a soil stabilisation process; measuring an electrical resistance value of an unsolidified grouting agent between said electrodes; and comparing said measured value with a preliminarily measured electrical resistance value of a sample having the similar conditions to said grouting agent and thereby predicting an after-solidification strength of said grouting agent in the unsolidified condition thereof.

10. A chemical grouting pipe assembly comprising a swivel joint including a terminal electrically connected to an electrode located on an outer wall of a grouting pipe rod, the electrode being rotatable relative to the terminal, the grouting pipe rod including at least one inner, co-axially extending rod which defines an inner passage and an outer passage, the cable extending through one of the passages, the other of the passages being arranged to carry the chemical.

11. A chemical grouting pipe assembly as claimed in Claim 10 when used in a method as claimed in Claim 5 or any other claim when dependent on Claim 5.

12. A chemical grouting pipe apparatus for use in soil improvement comprising: (a) A swivel having an electrical circuit closed between at least one terminal arranged at a head of said swivel and a cable connector positioned at a central portion of a lower end of said swivel through a slide brush and a cable; (b) A grouting pipe rod including a cable conduit having another cable connector at each end thereof and disposed centrally'in a concentric multi pipe; and (c) An electrode equipped grouting pipe rod including another cable conduit having still another cable connector at each end thereof and disposed centrally in another concentric multi pipe, and an electrode disposed on an outer wall thereof and connected to a lead wire extended from said another cable connector; said swivel, said grouting pipe rod and said electrode equipped grouting pipe rod being suitable connected to each other.

13. A chemical grouting pipe apparatus substantially as herein specifically described with reference to, and as shown in the accompanying drawings.

14. A method of surveying a region of soil to which a chemical has been added in order to stabilise the soil substantially as herein specifically described with reference to, and as shown in the accompanying drawings.