FI72995C - FOERFARANDE FOER STABILISERING AV KVICKLERA ELLER SALTLERAJORD. - Google Patents

Description

1 72995

A method for stabilizing rapid clay or salt clay

The invention relates to a method for stabilizing fast clay or salt clay.

5 Many clay layers often need stabilization before they can carry the additional load that comes during filling and construction. This is especially true of so-called fast clays, which are often found in, for example, the northern part of the Soviet Union, Scandinavia, Canada-10, New York State, and New Zealand.

The clays initially deposited in brackish water and seawater shortly after the last ice age, and later, during the (isostatic) rise of the continents, they rose above sea level. However, only some of these clay deposits 15 subsequently turned into sensitive fast clays. Such a change is mainly due to two processes. The initial salinity of the clay pore water may have come from the extract, by filtering the groundwater, or the organic matter from the supports or bogs, which acts as a dispersant, has entered the clay. The first process has been predominant with clays found in Norway, while fast clays with high organic matter content have been formed by the second process, and these clays are often found in Sweden and Canada.

25 Fast clays show a certain limited strength in the undisturbed state, but when disturbed they become completely fluid. The same phenomenon has caused several rapid clay landslides in the lowlands of eastern and central Norway, often with catastrophic consequences. To date, several chemical stabilization plans have been tried for such clays. In this case, e.g. the use of aluminum chloride (AlCl 2) and potassium chloride (KCl). Fast clays are stabilized in two ways. The clay can be mixed and treated with chemicals, or the chemicals can be allowed to diffuse into undisturbed clay. The disadvantage of the salt diffusion method is the long time it takes to achieve the required penetration of 2 72995. The diffusion method has only been used once, apparently, in its entirety in the field, when KC1-containing salt wells were installed two years before road construction.

5 To date, a method for deep stabilization using quicklime (CaO) has been developed. Lime is an old stabilizer that has been used occasionally. In China, it was used centuries ago as a building material. In the USA in the 1940s and in Europe in the 1950s, lime 10 was used as a surface stabilizer. The deep stabilization method involves mixing and pouring the lime with the clay to form a series of pillars extending down to the clay. These pillars cause lateral stabilization in the clay layer.

15 Both the lime and potassium chloride methods have disadvantages. KC1 stabilizes undisturbed, surrounding clay but not disturbed clay. Further, CaO causes inhomogeneous stabilization. The lime-forming pockets cause brittle cylinders with a low lateral shear strength. In addition, CaO cannot be used in clays with a high water content. Although aluminum hydroxide in the form of Al (OH) ^ 5Cl1q5 has not been used as a clay stabilizer in basic technology in the past, it has been used as a cementing agent in the preparation of desired clay microstructures in laboratory studies. Aluminum hydroxide solution containing KCl has also been used in trenches to treat formations containing water-sensitive clays and to stabilize sand. Relatively dilute solutions and overflows are used in this field. These methods are disclosed in U.S. Patents 3,603,399 (September 7, 1971) and 3,827,495 (August 6, 1974).

U.S. Patent No. 3,827,495 is the closest prior art to the present invention. However, the use of the chemical of the present invention, OH-A1, differs from the use of the chemical according to U.S. Patent No. 3,827,395, at least as follows: 3,729,515 1) The soil formations to be stabilized are clearly different

The stabilization method according to the present invention is used only for the treatment of fast clay or fast clay-like soil formations, while the The method of the U.S. patent publication is used to treat a wide variety of soil formations. Ko. However, the U.S. patent does not mention the treatment of rapid clay.

2) Stabilization mechanisms are different The procedure of U.S. Patent No. 3,827,495 takes advantage of the high tendency of a chemical to chemically associate with negatively charged sites on clay minerals. When cationic OH-A1 is adsorbed very tightly to the surface of the clay, it actually results in the clay behaving like an uncharged particle. As a result, the clay 15 is no longer capable of the conventional clay-water interaction that causes instability in wet clayey sands.

In contrast, the present invention takes advantage of another property of OH-Al, i.e., its ability to gel water at high OH-Al concentrations. The chemical is used as a minimal water-containing, i.e., dry, solid to gel as much of the in situ water associated with the rapid clay as possible. Gelation of water associated with rapid clay transforms the clay into a non-no-25 head clay with considerable structural integrity.

The process of U.S. Patent No. 3,827,495 does not take advantage of the gelling property of OH-Al. In fact, The procedure of the U.S. patent prevents the chemical gelling property of the chemical from being exploited.

3) The methods of adding the chemical are different According to U.S. Pat. No. 3,827,495, OH-A1 is injected into the sand as a relatively dilute solution and over-rinsed with an aqueous solution. The purpose of this is to cause 35 chemicals to adsorb to the reserved sites and an additional 4 72995 chemicals to leave the pores. Excess chemical is removed from the pores to prevent the formation of a gel, which otherwise tends to clog the pores.

In contrast, in the present invention, the chemical 5 is not injected into the soil formation, but is mechanically mixed with the rapid clay. A lot of chemical is intentionally left in the pores to promote gelation of water in situ.

The method according to the invention for stabilizing fast clay or salt clay provides a durable and effective stabilization of clay deposits. This process is characterized in that the rapid clay or salt clay soil is mixed with an effective amount of dry aluminum hydroxide of general formula A1 (OH) X 1, where n is 2.0 -2.7 and X is an anion which is chloride, bromide, iodide , nitrate, sulphate or acetate.

A chemical which is potassium chloride, potassium nitrate, potassium sulfate, ammonium chloride, ammonium nitrate or ammonium sulfate may be mixed with the aluminum hydroxide, of which potassium chloride is most preferred.

The mixture is preferably made in such a way that the stabilized clay forms a series of pillars extending into the clay layer, thus spaced apart so that the entire clay-containing layer is stabilized. The desired size, placement and number of pillars are decided. An effective amount of a dry mixture of aluminum-25 hydroxide and potassium chloride is mixed with the clay at each placement in the layer so that it reacts with the clay to form the desired pillars.

An effective amount means that sufficient aluminum hydroxide is present to impregnate the clay and to freeze the water added to or contained in the clay. This usually requires at least about 2.5 grams of aluminum hydroxide per 100 g of wet weight of clay soil in order to benefit from this invention. However, it will be appreciated that the clays 35 may be compressed, with a somewhat lower amount of aluminum hydroxy being effective. Potassium chloride 5 72995 is used to diffuse into undisturbed clay and should be sufficient to provide suitable diffusions.

Typically, the volume or size of the column to be formed in the clay-containing layer is determined, and the wet weight of the clay soil in such a column is also determined. A dry mixture of aluminum hydroxide and potassium chloride is formed. To obtain useful results, the dry mixture should contain at least 2.5 g of aluminum hydroxy-10 dia per 100 g of clay soil wet weight, and at least 1.0 g of potassium chloride per 100 g of clay soil wet weight. For optimal results, the dry mixture should contain at least 15 g of dry aluminum hydroxide and at least 10 g of dry potassium chloride per 100 g of wet weight of clay 15.

It is a particular object of this invention to provide a method of stabilizing a clay-containing soil layer by mixing a selected mixture of clay soils with a dry mixture, preferably containing an effective amount of aluminum hydroxide and potassium chloride, which react with the clay to form columnar plugs in the clay layer to anchor and stabilize it. The advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

Brief description of the drawings:

Figure 1 is a section of a clay-containing soil formation and schematically illustrates a preferred apparatus for mixing a dry chemical mixture with clay in situ in a soil formation in accordance with the present invention to form a stabilizing circuit for the soil formation.

Figure 2 is an enlarged schematic view of part 1 of the device of Figure 1.

Figure 3 is a schematic exemplary plan for the placement of columns to be formed to stabilize a clay soil formation under a road frame in accordance with the present invention.

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Figure 4 is a section of Figure 3 in direction 4-4.

Figure 5 is a schematic of an exemplary plan for the placement of pillars to be formed in accordance with the present invention under the foundations of a building or the like.

5 Figure 6 is a cross-section of Figure 5 in direction 6-6.

Figure 7 is a schematic sectional view of a test apparatus used for laboratory demonstrations of diffusion effects when the present invention is practiced; and

Figures 8-14 are diagrams showing experimental data necessary for understanding this invention.

The present invention stabilizes clay soil by mixing at least portions of such soil with an effective amount of a dry mixture of chemicals containing aluminum hydroxide and, if desired, the chemical potassium chloride, potassium nitrate, potassium sulfate, ammonium chloride, ammonium nitrate, or ammonium sulfate. Potassium chloride is the preferred chemical for mixing with aluminum hydroxide. In a preferred form, a plurality of columnar deposits are formed in situ in the clay soil layer when wet clay is mixed with a dry mixture 20 containing at least 2.5 g of dry aluminum hydroxide and at least 1.0 g of dry potassium chloride per 100 g of wet weight of clay soil. The best results are obtained when the dry mixture of chemicals contains at least 15 dry aluminum hydroxide and at least 10 g of dry potassium chlorine-25 slides per 100 g of wet weight of clay soil. Naturally, the optimum concentration of aluminum hydroxide may vary with different clays. The optimum concentration for a given clay can be determined by a simple laboratory experiment as described herein.

Aluminum hydroxide useful in accordance with this invention has a hydroxyl: aluminum ratio of at least 2.0. At low pressures with hydroxyl: aluminum ratios of less than 2.2, the materials tend to be so acidic that the carbonates contained in the clay soil are converted to carbon dioxide, which causes harmful bubbles in this invention. Therefore, in carbonate-containing soils, it is preferable to use aluminum hydroxide having a hydroxide to aluminum ratio of 2.5.

Thus, the aluminum hydroxy used in the present invention has the general formula Al (OH) nX 2 -n, wherein 5 n has a value of at least 2.0, preferably 2.5 to 2.7, and X is an anion which is chloride, bromide , iodide, nitrate, sulphate or acetate. For example, dry aluminum hydroxide chloride of the formula Al (OH) 2 tjClg 5 has been successfully used in the laboratory demonstrations of this invention. Aluminum hydroxide is a commercially available chemical and is supplied, for example, by Reheis Chemical Company, New Jersey,

Berkeley Heights or Hoechst Aktiengesellschaft, Frankfurt am Main, West Germany.

15 "Dry" aluminum hydroxide means a dry chemical to which no water has been added. Of course, dry aluminum hydroxide contains a substantial amount of chemically bound water. One Reheis product contains, for example, about 20-1 / 2% by weight of chemically bound water.

In a broad form, the present invention contemplates a chemical miscible with dry aluminum hydroxide that diffuses efficiently into undisturbed fast clay. Potassium chloride is a preferred chemical.

Other chemicals that have the desired effect are potassium nitrate, potassium sulfate, ammonium chloride, ammonium nitrate and ammonium sulfate. The salts of rubidium and cesium also have some beneficial effects, but these are not economically feasible for commercial use.

According to the present invention, a dry mixture of aluminum hydroxide and a chemical selected from the group consisting of potassium chloride, potassium nitrate, potassium sulfate, ammonium chloride, ammonium nitrate and ammonium sulfate is mixed with clay soil, and columnar expansions are formed in the clay soil. Preferably, the mixture is formed from aluminum hydroxide and potassium chloride. Preferably, the mixing is performed in situ by suitable mechanical means. In a preferred embodiment, the devices schematically illustrated in Figures 1 and 2 are used to mix the dry chemicals of this invention with normal, very wet clay soil. A particular device that can be used to mix the chemicals of this invention in situ is BPA Lindin-Alimak (Skelleft,

Sweden).

Referring to Figures 1 and 2, a clay layer layer 10 is shown. The drill-like apparatus generally indicated at 12 is shown for drilling a clay layer 15 in a hole 14 forming a pillar. The drill 12 includes a blade 16 and a hollow drill shank 18. A means (not shown) is provided for rotating the drill 12 and feeding dry chemicals into the drill and down the drill shank 18 for mixing with clay 10 in the hole 14.

Figure 2 shows the blade 16 in more detail. The blade is formed by a curved cutting element 20 which, when rotated, mixes the clay soil into which it advances. In the collar 24, in the lower part of the drill arm 18, there are several openings, 22a, b, etc. The dry chemical passes through the openings 22a, etc.

25 and comes into contact with the clay as the auger rotates and moves up or down, into and out of the clay layer. The dry chemical mixes with the wet clay and reacts and stabilizes the clay. The reaction is rapid, but does not occur immediately, so that mixing can occur both when the auger is driven down to the ground and when it is raised. This is a particular advantage of the present invention over the lime used hitherto. The reaction of the lime with the wet clay is so rapid that the lime could only be sprayed into the clay when the drill was removed from the 35 holes. Thus, the chemicals of this invention can be tested with clay more thoroughly in situ and ensure better results.

9 72995

Figures 3 and 4 show an example of a practical application of the present invention. Figure 3 is a schematic plan example of the arrangement of columns when the columns are formed in accordance with the present invention for clay stabilization under the road frame. Figure 4 is a section in the direction 4-4 of Figure 3.

The road frame 40 is illustrated in Figures 3 and 4. The road frame passes over an unstable clay layer, designated 42. In order to properly stabilize the clay layer 42 to withstand the stresses caused by the road frame 40, a series of pillar-like structures are generally designated. 44, a, b, c, by mixing aluminum hydroxide and potassium chloride with clay soil. Preferably, the pillars 44a, b, c are formed along the sides of the road body and directly below the road body. Note that the pillars not only support the road frame from below, but stabilize the clay layer on both sides of the road frame, including the slope supported by the pillars 44c.

Figures 5 and 6 illustrate another example of a practical application of the present invention. Figure 5 is a schematic plan example of the placement of columns when columns are formed in accordance with the present invention to stabilize clay soil under a foundation or building or the like.

25 Figure 6 is a cross-section of Figure 5 in the direction 6-6.

The foundation of the building is shown schematically in Figures 5 and 6 and is denoted by the number 50. The clay deposit 52 is below the foundation 50. A plurality of pillars, denoted by numbers 56a, b, c, are formed under, inside and outside the base 30 to 30 to stabilize the clay soil.

A series of laboratory demonstrations of clay stabilization were performed using the chemicals of this invention as well as other chemicals. These 35 demonstrations will now be described in detail with reference to Figures 7-14. Figure 7 is a schematic cross-section of a test apparatus used in laboratory demonstrations of diffusion effects using the method of this invention, and Figures 8-14 are diagrams showing the 5 curves obtained from the experimental data required to understand this invention.

Initially, two Norwegian clays were tested. These were Norwegian fast clay and sea salt clay. Almost all of the demonstration work was done with Norwegian fast clay. Table 1 shows the properties of these two 10 clays.

72995

table 1

Properties of Norwegian fast clay and sea salt clay

Clay type Fast Salt 5 Water content (1% of dry weight measured from the original clay as an average of each sample) 35.0-38.3 52

Shear strength (kPa measured by cone drop method) 7-10 7.0

Pore water chemistry pH 10 (ppm) 7.9-8.2 8.0

Na (ppm) 150-300 - K (ppm) 10-20

Ca (ppm) 10-40 (ppm) 3-20

Conductivity 6.4 ohms

CaCO- 1.4% organic carbon 0.6% salinity (expressed as N 2 Cltna) 0.4 g 20 g

NaCl / 1 NaCl / 1 grain size sand 1% 1% silt 57% 64% clay 42% 35%

Mineralogy (clay) (clay) 20 illite / muscovite 65% 30% chlorite 30% 10-15% quartz 0-5% 20% K-feldspar 15-20% plagioclase 5% 15-20%

Aluminum hydroxide chloride A1 (OH) 2, -Clq 5 (hereinafter referred to as aluminum hydroxide) has a stabilizing effect on Norwegian fast clay. Fast clay, which is very soft in its natural state, is fluid after disturbance. After the addition of aluminum hydroxide, the mixture is initially solid, and then softens to a somewhat smoother shape. Within minutes, the mixture polymerizes and after a few days it becomes hard clay. The addition of lime used so far has a somewhat similar effect. However, the difference between the aluminum hydroxide of the present invention and lime 35 as a stabilizer is in their way of influencing the surrounding undisturbed fast clay. Aluminum hydroxide has a stabilizing effect on a few centimeters of undisturbed clay, and the strength is about one tenth of the strength of the alloy. On the other hand, lime has 5 quite small effects on undisturbed clay.

Compared to KCl, which has also hitherto been used alone, aluminum hydroxide has much higher strength in the alloy, but KCl diffuses much faster into undisturbed fast clay and stabilizes if-to the extent of the clay several centimeters away from the alloy.

It has been found that the combination of OH-Al and KCl has the best properties of both stabilizers and gives a hard core from soft to medium hard undisturbed clay. Because the aluminum hydroxide alloy attracts 15 water, its strength decreases somewhat, to about a third in a few months, but overall this effect has only a minor effect on the beneficial effect of the present invention.

In general, laboratory demonstrations were divided into 20 two parts. The second part concerned the determination of the optimal mixing ratio (series A1) and the time dependence of dry aluminum hydroxide and aluminum hydroxide solution (series A2). The second part investigated the diffusion effects from stabilized clay to undisturbed clay.

In series B1 and B2, liquid and solid aluminum hydroxide are the only stabilizers, respectively. In series C1 and C2 it is mixed with KCl and in series D1 and D2 with methanol.

The demonstrations in the first part show the superiority of the use of dry aluminum hydroxide over the use of aluminum hydroxide solution. However, it is found that the aluminum hydroxide solution has substantial beneficial effects. Table II shows the aluminum hydroxide concentrations used in the Ai series. Note-35 distance that Ai refers to a special series, the next 13 72995 figure refers to the number of days elapsed before sampling and the letter refers to the segment number from the top where the test was performed.

Table II

5 In series A1, the following mixing ratio was used for concentration variations · ml 6.2M 0H-A1 or g OH-Al / 100 g no <g 0H-A1 powder / 100 g dry weight of clay clay mill -----—......

Al-la) 5 ml 6.2 M 3.62 10 A1 ~ 7a)

Ai-Ib) 5 ml 0.62 M 0.362

Al-7b)

Al-lc) 5 ml 0.062 M 0.0362

Al-7c)

Al-ld) 5 ml 0.0062 M 0.00362 15 Ai-7d)

Al-7e 0.8 1.09

Al-7 f 2.5 3.4

Al-7g δ 6.8

Al-7h 10 13.6

Al-7i 15 20.4 2Q In series A2, only 5 ml of 6.2M 0H-A1 / 100 g wet weight of clay was used for time variations with an experiment duration of 1 h (hour), 1 day (day), 3 days, 7 days, 30 days and 100 days. The same instruction was used for saline sea clay and is described in series A3, tau-25 in lock III.

The clay was mixed and placed in a plastic container with a lid. This was covered with plastic films and set aside in a container of N 2 gas and stored at 7 ° C. Shear strength was measured from each of the 30 samples. Some were compressed and the pore water was measured for pH, and in some cases Ca, Mg, K and Na were measured by atomic absorption.

The results of the demonstration series performed as described are shown in Table III.

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The results shown in Table III show that the results obtained with dry aluminum hydroxide are better than those obtained with aluminum hydroxide solution. The concentration of the aluminum hydroxide alloy ranged from 0-15% of the wet weight (or 0-20% of the dry weight) of the clay (series A1). The results shown in Table III show that the shear strength varies from the strength of the liquid (<0.1 kPa) to the strength of the hard packed clay (> 375 kPa) as the amount of aluminum hydroxide increases. Comparison of the liquid mixture with the dry mixture shows that the addition of water with aluminum hydroxide reduces the stabilizing effect.

Small dry additions of aluminum hydroxide (to about 5%, i.e. 8% dry weight) make the clay deformable immediately. When small additions of alumina hydroxide made the clay immediately deformable, the larger additions first made the clay stiffer, but after stirring for one minute, it became looser. It then acquired a smooth character and gradually turned into harder clay. If the solid aluminum hydroxide is not suitably mixed, it will attract water and form a brittle gel.

The clay and aluminum hydroxide solution were mixed in a standard ratio of 5 ml of 6.2 M OH-A1 per 100 g of wet weight of clay and set aside for one hour, 1 day (day-25 days, 3 days, 7 days, 30 days and For 100 days The shear strength tests were performed and the results are given in Table III The tests marked with an asterisk * were performed later than other perhaps less oxidized clay.

It should be noted that the shear strength rises above the value of undisturbed clay after a few minutes.

Saline sea clay and OH-Al were mixed in a standard ratio of 5 ml of 6.2 M OH-A1 to 100 g of wet weight of clay and set aside for one hour, 1 day, 3 days, 7 days, 30 days and 100 pVrksi. Surgical bone-35 hair was measured and the results are shown in Table III.

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Due to the very high water content of the clay, the additional water brought in by the liquid OH-Al made the clay into a fluid form.

Salted sea clay disturbed for 100 days did not reach its original shear strength. In this case, the results are apparently better with dry aluminum hydroxide.

The two demonstrations of the diffusion effects of stabilized clay will now be elucidated in detail. Diffusion experiments used small brass-10 cylinders with a diameter of 35 mm and a height that varied, this is schematically illustrated in Figure 7. The cylinders were closed from the bottom and the top 5 cm above the disturbed clay was filled with the mixture. As shown in Table IV, the disturbed clay mixture in the reported series contained: 15 Table IV

Bl 5 ml 6.2 M OH-A1 / 100 g wet weight of clay B2 15 g OH-A1 powder / 100 g wet weight of clay Cl 5 ml 6.2 M 0H-A1 + 9.5 g solid KCl / 100 g wet weight of clay 20 C2 15 g OH-A1 powder + 9.5 g solid KCl / 100 g wet weight of clay

Dl 5 ml 6.2 M OH-A1 + 5 ml methanol / 100 g wet weight of clay D2 15 g OH-A1 powder + 5 ml methanol / 100 g clay 9 25 wet weight The samples were covered with plastic and set aside for 7 days ), For 30 days and for 100 days in a tank filled with 7 ° C. The uniformity of the mixtures caused only minor problems. The disturbed clay in series B was 30 liquid, in series C dry and flexible, and in series D-sa wet and flexible.

After storage, the clay columns were pushed out and the shear strength was measured. Later, the clay was cut into 2.5 cm slices. From each slice, the water content was measured from one portion and the other portion was compressed, and the pH was measured and analyzed for Ca, Mg, K, and Na pore water by atomic absorption. Tables V-IX and Figures 8-14 illustrate the results of these demonstrations.

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25 7 2 9 9 5 In these tables, the serial number is followed by a sample number indicating the duration of the experiment in days. The third number describes the segment number calculated from the top of the cylinder down. For example, C2-30-3, where C-2 denotes 5 solid OH-A1 mixed with KCl, 30 denotes a duration of 30 days and 3 denotes the third segment from above.

Shear strength is measured for each segment.

The method used is a cone-dropping method, in which the sharp cone digs into the clay by its own gravity.

The number of millimeters that the cone has dug is converted to 2 kParks (kN / m) by a standard curve. Other parameters measured were water content (as a percentage of dry weight), pH, and Ca, Mg, 15 K, and Na content of compressed pore water. Elements were measured by atomic absorption with an accuracy that can achieve + _ 60% uncertainty in some results. As a reference to the experiments, natural fast clay was analyzed for mineralogy, grain size distribution, cation exchange capacity, inorganic and 20 organic carbon, and salinity.

In the demonstrations of Part 2, as shown in Tables V-IX and Figures 8-14, undisturbed clay cylinders were used. The length of the cylinders varied between 10-30 cm. Some of them contained bridging layers that caused variations in shear strength and water content, and most likely also contributed to some diffusion.

The inhomogeneity of the cylinders can cause interference when the clay is pushed into the cylinders and when it is pushed out. Sometimes the disturbances caused the water accumulated in the bottom to dry out.

Oxidation of the clay was prevented because the cylinders were stored under an atmosphere of 7 ° C.

As shown in Figure 7, the disturbed clay 35 stabilized with either aluminum hydroxide and 26 7 2 9 9 5 KCl or aluminum hydroxide and methanol or aluminum hydroxide alone was placed on top of the cylinders. The cylinders were then covered with several layers of plastic and set aside for 7, 30, or 100 days.

5 At the end of each experiment, the clay was pushed out and the various parameters were measured downwards from the cylinder.

After disturbing and mixing with the 6.2 M aluminum hydroxide solution, the clay becomes rigid (60 kPa) and remains rigid (50-80 kPa) throughout the test.

10 Tables V and VI show rather low shear strength values in undisturbed clay due to diffusion. The effectiveness and permeability of the stabilizing effect are not clear.

The water content indicates that the aluminum-hydroxy-15 mixture mixes water out of the undisturbed clay.

This effect is also observed in all other experiments.

The pH also has a much similar development in all experiments. Aluminum hydroxide has an acidic reaction that penetrates down the column to some extent, but neutralizes over time.

The chemistry of the pore water is much similar in the three experiments. There are two exceptions: very high potassium release in the Bl-30 series and high magnesium content in the Bl-7 series.

25 Interference of rapid clay with aluminum hydroxide apparently releases a substantial amount of cations into the pore water. For example, the potassium content increases almost 10-fold, magnesium about 100-fold and calcium more than 200-fold. The resulting difference in concentration between the disturbed and undisturbed clay results in the diffusion of cations into the undisturbed clay.

The dry aluminum hydroxide mixture gives much better geotechnical results compared to the aluminum hydroxide solution mixture. The disturbed clay immediately acquires 35 higher shear strength, which over time decreases from 27 72995 to about 1/3 of the original value, as shown in Tables V, VI, VII and VIII. The stabilizing effect over time on undisturbed clay is less ambiguous with dry aluminum hydroxide than with aluminum hydroxide solution. Penetration series into the original clay develop an average strength (25-50 kPa) of 4-9 cm down the column over the test period.

Measurements of water content confirm the osmotic effect of the already predicted aluminum hydroxide.

Disturbed clay contains 30% more water than undisturbed clay after 100 days. pH measurements also confirm the acidic reaction of aluminum hydroxide. The difference between disturbed and undisturbed clay can be at least 2 pH units. Pore water chemistry shows much the same trend as previously described. However, for an unknown reason, the B2-100 series shows greater release of Ca, Mg, and Na. Compared to the aluminum hydroxide solution, dry aluminum hydroxide releases K and Mg equally (factor 10 or 100) but somewhat less Ca (factor 100-200).

As shown in Table VI, mixing 6.2 M aluminum hydroxide solution and solid KCl 25 gives a rigid, disturbed clay with a shear strength of 50-80 kPa and independent of the duration of the experiment. Diffusion down in the disturbed clay causes a medium-strong clay (25-50 kPa) to a depth of 6 em (B1-7) and 11 emm (B1-30). The increased shear strength in undisturbed clay compared to aluminum hydroxide-30 alone solution is probably due to the diffusion of potassium ions.

Water content measurements show that the water has dried somewhat in the Cl-7 series. However, it is not possible to observe the osmotic effect of aluminum hydroxide __ - f 28 7 2 9 9 5 as previously expressed. pH measurements show a large difference between stabilized and undisturbed clay (at least 2.5 pH units) at the beginning of the experiments. Over time, acid (H +) 5 penetrates down the column and slowly neutralizes.

There are no different trends in pore water chemistry compared to the experiments already described, a large increase in potassium. For one-dimensional diffusion constants, K has been estimated in both experiments in the Cl series.

_g 2 10 The approximate values are 6 x 10 cm / s for the 7-day test and 3 x 10 cm / s for the 30-day test. The values are approximate because there is no precise information on the concentration of the tank, or on the stability of the tank concentration, the inhomogeneity of the clay and the chemical reactions or physical changes of the clay have not been taken into account. The concentrations of Mg and Ca in the pore water are much the same as in series B1.

Table VII shows the results for dry aluminum hydroxide and potassium chloride as stabilizing chemicals. This mixture gives a hard disturbed clay with an initial shear strength of 300 to 400 kPa and decreases to 100-200 kPa during the test. Diffusion downwards in undisturbed clay causes a medium rigid clay (25-50 kPa) to a depth of 5 cm (C2-7), a depth of 10 cm (C2-10) and a depth of 20 cm (C2-100). It should be noted that the maximum shear strength in undisturbed clay increases slightly during the test period. As in series Cl, potassium diffusion is the main reason for this increased shear strength.

30 Measurements of water content show the same development as previously described. The water content of the stabilized mixture increases by about 30% from 7 to 100 days; however, the water content of the undisturbed clay has not been accurately reported in the undisturbed clay measurements.

29 7 2 9 9 5 pH measurements are only available from undisturbed clay and show only a slight increase down the pillar. This trend is similar to that described earlier.

There are no significant differences between this and the previously described pore water chemistry results. For the one-dimensional diffusion coefficient, K was estimated in three "" 6 2 -6 experiments and the values were 4x10 cm / s (C2-7), 4x10 2 - cm / s (C2-30), and 3x10 cm / s (C2-100). The Ca and Mg content of the pore water was much the same as in the B2 series.

Demonstrations were performed with an aluminum hydroxide solution containing methanol. The results are given in Table VIII. This mixture gives a fairly soft, disturbed clay that partially becomes liquid during test time (Dl-100). The biliary effect of diffusible substances seems to be rather small. Only the top 1 cm of undisturbed clay has a shear strength of more than 25 kPa at the beginning of the period, with a few additional centimeters giving values between 15 and 25 kPa. These results are not far from the B1 series, indicating that the positive effect of added methanol is negligible.

Measurements of water content clearly do not indicate that the mixture attracts water, probably due to the excess liquid content of methanol. The pH measurements clearly show the pH gradient and H + diffusion from the source along the column downwards. The pore water chemistry values are much similar to those previously described.

Demonstrations were also performed with dry aluminum hydroxide with methanol as a stabilizer. Table IX shows the results. The mixture gives a rigid mixture of very rigid disturbed clay (about 100 kPa) in 7 days. After 30 days, however, the shear strength has dropped to an average clay value of 35 (about 40 kPa). Unfortunately, the D2-100 series were destroyed, __ - r 30 7 2 9 9 5 and no shear strength results were obtained. It should be noted that the upper 3 centimeters of the disturbed clay became liquid, the next centimeters very soft and the last centimeters stiff or very stiff-5 k. In undisturbed clay, the shear strength increased to an average clay value (25-50 kPa) of 4 cm down the pillar over 7 days, and 7 cm over 30 days. It was impossible to estimate penetration in the D2-100 series.

10 Measurements of water content show large irregularities, but it is obvious that the mixture attracts water and even converts the disturbed clay into a liquid. The pH gradients have the same trends as previously described. Pore water chemistry also shows 15 the same concentrations and trends as in other series with dry aluminum hydroxide. However, especially in the D2 series, the penetration (penetration) of substances into undisturbed clay is somewhat slower.

Figure 8 shows a comparison of the aluminum hydroxide solution without additives and with several additives after 7 days. The mixture of aluminum hydroxide solution gives a rigid clay mixture (65 kPa) after 7 days. The addition of KCl does not cause changes, but the addition of methanol li-25 reduces the shear strength to about 30 to about 30 kPa, probably due to the addition of extra water. In undisturbed clay, the aluminum hydroxide solution causes very little increase in shear strength and to a depth of only a few centimeters. The addition of methanol 30 gives a slightly more efficient increase in shear strength to the same top few centimeters. The addition of KCl increases the shear strength to a greater depth than the previous two. The reason is probably the addition of potassium, but part of the increase in shear strength may have been caused by 35 released diffusion agents such as Ca and Mg.

72995

Figure 9 shows a comparison of dry aluminum hydroxide without additives and with several additives after 7 days. The dry aluminum hydroxide alloy increases the shear strength of the disturbed clay to about 300 5 kPaz (hard clay). A mixture of dry aluminum hydroxide and KCl gives approximately the same shear strength, while the addition of aluminum hydroxide with methanol gives a shear strength of 100 kPa. The lower strength obtained with methanol is 100 kPa. The lower strength obtained with methanol is probably due to the addition of liquid.

The increase in shear strength of undisturbed clay is much the same in all three experiments as with medium-stiff clay (25-50 kPa) to a depth of 4-5 cm. The differences between the series with and without KCl are also shown by pore-15 water chemistry, where the Ca, Mg, and K values are almost everywhere higher when KCl is added. In the D2 series, the shear strength is higher than all others and may be due to either the Ca concentration in the pore water or the methanol content.

Figure 10 shows a comparison of aluminum hydroxide alone and. with various additives after 30 days. Addition of the aluminum hydroxide solution gave a shear strength of about 70 kPa in the disturbed clay; almost the same value as the mixture of aluminum hydroxide solution and 25 KCl (about 60 kPa), when the aluminum hydroxide solution with methanol only reached 30 kPa.

In undisturbed clay, the aluminum hydroxide solution with or without methanol follow each other to a large extent. Their strength is about 20 kPa 30 7-8 cm pillars downwards, although the pore water chemistry of the series is not the same. The mixture of aluminum hydroxide solution and KCl is much more effective than the others because it gives a medium rigid clay of 11 cm. pillars down. With the exception of the first two centimeters, the Ca-35 and Mg content of the pore water and, of course, the K content are much 32,729,55 higher in the Cl-30 series than in the others, and this may result in higher values of shear strengths.

Figure 11 shows dry aluminum hydroxide data after 30 days. Dry aluminum hydroxide-5 alloys give greater dispersion in shear strength values for different additions. The dry aluminum hydroxide mixture gives about 100 kPa to the disturbed clay, while the aluminum hydroxide and KCl additions are much more effective, values of 300-400 kPa. On the other hand, a mixture of aluminum hydroxy-10d and methanol causes a lower shear strength of 30-60 kPa. In undisturbed clay, the mixture of aluminum hydroxide and methanol is most effective at the first 2 cm (about 35 kPa), as in the 7-day series. The next 7 cm has the highest shear strength (25-35 kPa) with a mixture of aluminum hydroxide and KCl. The shear strengths of the different mixtures have a greater difference after 30 days than after 7 days. In this series (B2-30, C2-30, and D2-30), there is no obvious relationship between the shear strength of undisturbed clay and pore water chemistry 20, as previously described.

Figures 12 and 13 show a comparison of different stabilizers after 100 days. The mixture of aluminum hydroxide solution gives a rigid clay (50-80 kPa) after up to 100 days, while the mixture of aluminum hydroxide solution and methanol gives values ranging from the value of liquid clay (<0.1 kPa) in the upper 3 sms to 40 kPa in the lower 2 sows. The experiment was not performed with aluminum hydroxide solution and KCl.

The mixtures have little effect on undisturbed clay. The shear strength hardly exceeds 15 kPa at a depth of 7 emi with a mixture of aluminum hydroxide and methanol and only to a depth of 1 emi with aluminum hydroxide solution alone. The shear strength of undisturbed clay decreases in 7-30 day experiments with aluminum hydroxide solution. 35 As shown in Figure 13, the addition of dry aluminum hydroxide to the fast clay gives a shear strength that increases from 90 to about 400 kPa in the top-down disturbed clay. This result is close to the addition of dry aluminum hydroxide and KCl to give 5 results that vary in the same values. The experiment with dry aluminum hydroxide and methanol was destroyed and no shear strengths were obtained. In this case, the top 3 cm was in the running state.

In the disturbed clay, the shear strength exceeded 10 to some extent the results of the 30-day series. With dry alumina hydroxide alone, the shear strength ranged from 20 -50 kPa to a depth of 9 cm, 4 cm of which exceeded 40 kPa. On the other hand, a mixture of dry aluminum hydroxide and KCl gives shear strengths between 25-50 kPa at a depth of 14 cm 15 and values above 20 kPa in addition to a depth of 7 cm. There is a relatively good correlation between shear strength and pore water Ca, Mg and K concentrations.

Figure 14 shows a comparison of the stabilization of dry aluminum hydroxide alone, KCl and CaO after 100 days. A comparison of the shear strengths in the disturbed clay shows that the dry aluminum hydroxide mixture achieves a stiffness that exceeds the value of CaO. This may be a coincidence, as a second mixing ratio and better sealing can increase shear strength.

25 KC1 alone does not provide stabilizing effects.

In undisturbed clay, the stabilizing effect is limited. At a distance of 3 cm under CaO-stabilized clay, the shear strength drops to 100 -> 20 kPa. With dry aluminum hydroxide it drops 50 -> 20 kPa by 9 cm 30 pillars downwards when KCl has a value of 20-25 kPa to a depth of 19 cm. The increased value of shear strength in undisturbed clay is due to the high water absorption effect of lime in CaO stabilization. Aluminum hydroxide also has, as previously described, a water-attracting effect, but in this case only- - -. ......

34 7 2 9 9 5 spawning extends deeper into the pillar, probably due to the higher cation content. In the lime stabilization experiment, the upward movement of water is masked by a chemical reaction of CaO + H 2 O - KCl probably has no effect on water content.

Dry aluminum hydroxide alone is a very promising stabilizer. For practical reasons, the mixing ratio of aluminum hydroxide to clay should be 15% (relative to the wet weight of the clay). Optimal results can be obtained even with high ratios. The high aluminum hydroxide ratio is expected to further increase the shear strength in the disturbed clay.

Even more important, from a geotechnical point of view, are the results of aluminum hydroxide mixed with KCl. Surprisingly, KCl in disturbed clay does not reduce the strength effect achieved with dry aluminum hydroxide alone. In disturbed clay, where aluminum hydroxide has less of an effect, KCl diffun-20 decomposes relatively rapidly and forms a stabilized region deeper into the clay. Aluminum hydroxide does not interfere with this property of KCl.

From the above description, it is apparent that the present invention provides a method for stabilizing the clay of said deposits by mixing dry aluminum hydroxide and potassium with clay soil. Although only specific embodiments of the present invention have been described in detail, the invention is not limited thereto, but is intended to include all applications that may come according to the appended claims.

Claims (9)

35 7 2 9 9 5 A process for stabilizing fast clay or salt clay, characterized in that the fast clay 5 or salt clay is mixed with an effective amount of dry aluminum hydroxide of the general formula Al (OH) n ^ 3-n, where n is 2.0-2, 7 and X is an anion which is chloride, bromide, iodide, nitrate, sulfate or acetate. Process according to Claim 1, characterized in that at least 2.5 g of aluminum hydroxide are mixed per 100 g of wet weight of clay soil. Process according to Claim 1, characterized in that at least 15 g of aluminum hydroxide are mixed per 100 g of wet weight of clay soil. Process according to Claim 1, characterized in that a chemical which is potassium chloride, potassium nitrate, potassium sulphate, ammonium chloride, ammonium nitrate or ammonium sulphate is mixed with the aluminum hydroxide. Process according to Claim 4, characterized in that the mixture of aluminum hydroxide and chemical is dry. Process according to Claim 5, characterized in that the dry mixture contains at least 2.5 g of aluminum hydroxide per 100 g of clay soil wet weight and at least 1.0 g of chemical per 100 g of clay soil wet weight. Process according to Claim 5, characterized in that the dry mixture contains at least 15 g of aluminum hydroxide per 100 g of wet weight of clay soil and at least 10 g of chemical per 100 g of wet weight of clay. Process according to Claim 5, characterized in that the chemical is potassium chloride. Method according to one of the preceding claims, characterized in that the clay soil is stabilized by forming a plurality of columns extending into said formation, selecting the size of the columns to be formed, determining the wet weight of the clay in the columns and mixing aluminum hydroxide or aluminum hydroxide and potassium chloride with clay to form pillars. 37 72995