BACKGROUND OF THE INVENTION Sprayed concrete (also called"shotcrete") is used widely for slope protection.

The main function of sprayed concrete is to provide an"impermeable"cover to reduce surface infiltration into slopes and to protect slopes from surface erosion.

However, slopes with sprayed concrete cover are notorious for their problems including the following: 1) Slope failure due to built-up porewater pressure behind the sprayed concrete cover -weepholes are used as an inexpensive means to control the ground water seepage in sprayed concrete covered slopes. However, the effectiveness of these weepholes quickly deteriorates as they become blocked by fines washed out from the slopes or simply blocked by vandals. Once blocked, they can no longer intercept and drain seepage in order to control groundwater levels behind the slopes. In areas with complex soil conditions, the limited number of weepholes may not intercept and drain the water bearing zones in the slope. As groundwater level rises behind the slope, and pore water pressure built-up will cause failure of the slopes ; and 2) The dull, gray colour plus the wear and tear of the sprayed concrete becomes an unattractive eyesore.

SUMMARY OF THE INVENTION In view of the serious shortcomings of sprayed concrete-covers, we have developed a new slope protection system.

The invention is a novel, innovative, and unique way of permanently rendering exposed steeply inclined soil slopes, rock slopes and sprayed concrete covered slopes green with natural indigenous vegetation. The invention utilizes two incompatible materials, soil and concrete, in a unique way.

Concrete is a well-known construction material. It is often composed of cement,

clean sand, crushed stone, and water, mixed in various proportions, to produce concrete. Other variations are known.

Unlike concrete, soil is a natural material. It is a mixture of organic and inorganic substances. The organic components of soil are derived from the biodegradation of dead plants and animals. The inorganic components are the result of chemical and physical decomposition of rocks, and subsequent erosion, transportation and deposition by wind, water and ice.

The invention is a unique type of soil and cement shotcrete that satisfies both these objectives, at a competitive cost. It is a mixture of soil and concrete prepared in a unique manner, but applied more or less in the same conventional manner as shotcrete. The soil component of biocrete is embedded in the form of"bio-capsules" (also called"capsules"or"bio-balls') within the biocrete mixture. After application of the biocrete to the slope face, these bio-capsules allow indigenous vegetation to grow and thrive. The end result is a natural looking slope face with many advantages, especially in an urban environment.

The biocrete system preferably incorporates four layers which are placed against the exposed soil or rock slope face: (1) a drainage layer to collect and safely transport seepage water originating within the soil or rock mass and flowing outwards towards the slope face; (2) a water barrier above the drainage layer to prevent entry of surface water when the bio-bed surface is wetted to support vegetative growth; (3) the bio-bed made of biocrete material; and (4) the growth bed.

Biocrete materials preferably include: . Portland cement (or other types of cement), clean sand and water (preferably potable quality water); Loam (or soil which can support and encourage vegetation); Organic fibre; Soil nutrients and grass or plant seeds; Smectite, a class of clay mineral, absorbs large quantities of water in proportion to its weight, and thereupon expands proportionately. A commercial form of smectitic clay is"bentonite".

The method of the invention involves the inclusion within the concrete mixture, and delivery of, discrete plant growth soil cells, known as"bio-capsules", using conventional shotcrete application equipment. The bio-capsules may range in size typically from 2 mm to 30 mm. Their concentration within the sprayed concrete matrix creates connected"channels"for root growth and sustenance of plant life.

Since both the bio-capsules and the concrete mix are applied simultaneously, the concrete forms a hardened cover on the surfaces of the bio-capsules, making it difficult for seed germination and plant growth. The bio-capsules are usefully coated with bentonite powder before being mixed with the concrete. The bentonite absorbs water from the concrete mix and expands, exerting pressure which breaks down the outer covering of concrete, thus exposing the soil within the bio-capsules for seeding, seed germination, and plant growth.

The invention can be used as a slope greening and surficial slope stabilizing technique to a variety of slope related situations, such as newly formed slopes, slopes with or without drainage problems, and eroding vegetated slopes. Figures 1 to 5 illustrate schematically the general arrangement of the biocrete system in relation to these four specific types of slope management problems.

The environmental benefits of the invention include: natural greening; cleaner air, especially within heavily populated urban areas; and, the removal of aesthetically unpleasant shotcrete facing.

The choice of vegetation that is used with the biocrete system will be such as to ensure that it can sustain itself from the available amounts of soil and nutrients. This eliminates the need for periodic maintenance, such as the mowing of conventional grassed slopes, or the re-application of new shotcrete to cover failed or aesthetically unpleasant older shotcreted slope faces.

The advantages of the invention include : 1. The use of two generally incompatible materials, soil and concrete, in a synergistic manner; 2. The long term co-existence, without major adverse effects on either, of an alkaline and an acidic environment; 3. The use of an expansive clay mineral, such as bentonite, to enable the bio-capsules

to expand and crack any hardened concrete around them, in order to encourage seed germination and plant growth; 4. The use of different layers along the slope face to facilitate the success of the biocrete system; 5. The ability of the biocrete system to address a variety of disparate common shallow slope failure problems; 6. The ability of the biocrete system to permanently and naturally render green any soil slopes, rock slopes and sprayed concrete covered slopes, regardless of its angle of inclination with respect to the horizontal, preferably using only natural indigenous plants and/or grasses.

A strong advantage is the mixing of soil and concrete together in such a way that each retains its distinctive properties and advantages without affecting those of the other. Bentonite coated bio-capsules are a means of conveying life-supporting soil simultaneously with the much stronger concrete to a pre-stabilized exposed soil or rock slope face. The effectiveness results from the permanent natural greening of slopes treated with the biocrete system.

The invention also includes a process for preparing the capsules, preferably in the form of balls having diameters between 2 mm to 30 mm. The process includes mixing by stirring a composition including soil, fibre and lawn seed fertilizer; passing the mixture into a receptacle and mixing a measured amount of seed (such as lawn grass seed) into the composition to provide a substantially even germination density of the seed; forming the material into capsules (for example by forming capsules by spinning in a turn-table or by a pressure applying mold device) and optionally coating the capsules with bentonite.

The biocrete system is preferably a combination of four layers. In some cases, a biocrete system may contain: 1) Growth bed + bio-bed +drainage layer + impermeable layer 2) Bio-bed alone 3) Growth bed + bio-bed 4) Bio-bed + drainage layer

5) Bio-bed + impermeable layer Examples of systems, (the % in bracket are a suggested range). bio-capsule mix: 100kg (+-30%) clayey silt or loam, 5kg (+-20%) wood powder glue, 3 kg (+-20%) inorganic fertilizer, 10kg (+-25%) bentonite (coating), 120g (+- 100%) seed. bio-bed mix: 30kg (+-20%) cement, 70kg (+-40%) sand, 46kg (+-30%) crushed stone, 88kg (+-30%) bio-capsules, 10kg (+-100%) rice husk. drainage layer: 60kg (+-20%) cement, 240 kg (+-35%) sand, 30kg crushed stone (+- 100%), 6 kg (+-100%) rice husk.

Another example of a system is: bio-capsule mix: 100kg (+-25%) clayey silt or loam, 0. 5kg (+-25%) wood powder glue, 3 kg (+-25%) inorganic fertilizer, lkg (+-25%) bentonite (coating), 120g (+- 100%) seed, 3 kg (+-20%) organic fibre, lkg (+-20%) water retenting polymer. bio-bed mix: 70kg (+-25%) cement, 70kg (+-25%) sand, 146kg (+-25%) crushed stone, 170kg (+-25%) bio-capsules, 5kg (+-25%) rice husk, 2. 5kg (+-25%) water retenting polymer. drainage layer mix: 60kg (+-20%) cement, 240 kg (+-35%) sand, 30kg crushed stone (+-100%), 6 kg (+-100%) rice husk. growth bed mix: 450 kg (+-25%) sand, 30kg (+-25%) organic fibre, 5kg (+-25%) wood powder glue, 2kg (+-25%) water retenting polymer, 5kg (+-25%) seeds.

The invention includes 1) bio-capsule mix 2) bio-bed spray method 3) bio-capsule application, 4) drainage layer mix, 5) drainage layer spray method, 6) growth bed mix, 7) growth bed spray method.

A variation of the system includes : bio-bed mix (ratio by weight) cement : sand : crushed stone : bio-capsules 1 : 1. 8 (+/-10%): 1.8 (+/-10%): 2.8 (+/-10%) plus preferably 0% to 5% of curing agent Another variation of the bio-capsule mix (ratio by weight):

clayey silt : fertilizer water : binding agent 1 : 0.1 (+/-20%): 0.2 (+/-20%) : 0.02 (+/-80%) Another bio-bed mix (ratio by weight) is as follows: cement : sand : crushed stone : bio-capsules: rice husk : water retenting polymer 1 : 1 (+/-25%) : 2 (+/-25%): 2.4 (+/-25%) : 0.07 (+-25%): 0.035 (+-25%) plus preferably 0% to 5% of curing agent Another variation of the bio-capsule mix (ratio by weight): clayey silt : fertilizer : water: binding agent : bentonite : organic fibre 1 : 0.03 (+/-25%) : 0. 05 (+/-20%) : 0. 005 (+/-25%): 0.3 (+- 100%): 0. 1 (+-25%) In one embodiment, the invention relates to a method of stabilizing an inclined surface against erosion comprising: applying over the surface a layer including (a) a structural matrix for retaining the surface and (b) a growth composition dispersed in the matrix, the growth composition capable of supporting vegetative growth. Another embodiment of the invention relates to a system for stabilizing an inclined surface against erosion comprising: a layer including (a) a structural matrix for retaining the surface and (b) a growth composition dispersed in the matrix, the growth composition capable of supporting vegetative growth.

In the method and system, the layer comprises organic matter capable of supporting vegetative growth, cement, aggregate and organic fibre. The structural matrix and growth composition usually include natural compounds. Preferably the structural matrix includes a water retenting agent. In one variation, the structural matrix is substantially free of synthetic polymer. The structural matrix preferably includes an inorganic matrix. The inorganic matrix preferably includes a composition that is fluid when it is applied over the surface and which cures to a rigid matrix. The structural matrix preferably includes concrete. The concrete is preferably shotcrete, including cement, aggregate and water. In one embodiment, each kg of the structural

matrix applied to the surface initially comprises between about: 60 and 200 gm. of cement, between 300 and 800 g of aggregate having a sieve size between 0.16 mm and 10.0 mm, and between 30 and 120 gm of water. In another embodiment, each kg of the structural matrix applied to the surface initially comprises between about: 150 and 250 gm. of cement, between 500 and 700 g of aggregate having a sieve size between 0. 16 mm and 10. 0 mm, and between 150 and 250 gm of water. The growth composition preferably includes a mixture of inorganic and organic compounds. The growth composition also preferably forms connected channels in the structural matrix for vegetative growth. The method of the invention, wherein the growth composition is formed from capsules, preferably ball-shaped, having a diameter of 2 mm to 30 mm or 5 mm to 30 mm. The capsules usefully comprise clayey silt, organic and inorganic fertilizer, chemical fertilizer, water and binding agent in the ratios of 1 clayey silt: 0.02 to 0.2 fertilizer: 0.1 to 0.3 water: 0.01 to 0.05 binding agent. The capsules also usefully can comprise clayey silt, organic and inorganic fertilizer, chemical fertilizer, water and binding agent in the ratios of 1 clayey silt: 0.02 to 0.1 fertilizer: 0.01 to 0.1 water: 0.01 to 0.1 binding agent. The growth composition preferably includes soil, and usefully includes one or more compounds selected from the group of a binding compound, fertilizer, organic filler and seed. The growth composition can further include a binding compound, fertilizer, organic filler and seed and a swelling agent.

Optionally, the binding agents include a tree gum or fibre, the soil comprises clayey silt, the seed comprises grass seed, the organic filler comprises manure, nitrogen fertilizer, potash fertilizer or peat moss and the swelling agent comprises bentonite. The fibre may include shredded paper. The grass seed is preferably dispersed at a density suitable for germination of the seed.

The bio-bed layer can comprise between 24 and 36 kg of cement, between 75 and 160 kg of aggregate, between 62 and 114 kg of bio-capsules, between 0.1 and 20 kg of organic matter and between 1 and 2 kg of curing agent.

The layer may be formed by dry or semi-dry application spraying the layer with a shotcrete gun onto the surface. Water is typically added to the layer at the shotcrete gun nozzle. The layer can be sprayed 20 mm-200 mm thick. A growth bed may be sprayed over the bio-bed layer. The growth bed layer preferably includes 30 to 50 kg of top-soil, 2 to 5kg of organic fibre, 2 to 5kg of wood powder glue, 1 to 3 kg of water

retenting polymer and 0.4 to 0. 8kg of seeds.

The system and method may further include a water barrier layer between the surface and the bio-bed layer, the water barrier layer having very low water permeability in order to reduce flow of water from the layer into the surface. In one embodiment, the water barrier comprises mortar. The method and system preferably further comprise a drainage layer between the layer and the surface, the drainage layer being porous and water permeable to prevent water from the surface from applying pressure on the layer. Another variation comprises a water barrier layer and a drainage layer, wherein the water barrier layer is proximate to the layer and the drainage layer is proximate to the surface. The drainage layer can include lean mix concrete with substantially uniform sand.

The invention also includes a shotcrete additive comprising a growth composition capable of supporting vegetative growth. The additive preferably includes a mixture of inorganic and organic compounds. The growth composition may be as defined in this application (for example, formed into capsules, such as balls).

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention will be described below in relation to the drawings in which: Fig. 1 shows a preferred embodiment of the invention ; Figs. 2 (a) and (b) show a variation of the invention to solve a Type I problem in newly formed slopes. The drainage blanket intercepts the water table and drains the water away. The two water tables are the same; Figs. 3 (a) and (b) show a variation of the invention to solve a Type II problem in slopes without drainage problems. The water table is not lowered. The two water tables are the same; Figs. 4 (a) and (b) show a variation of the invention to solve a Type III problem in slopes with drainage problems. Water is the problem and figure b shows the effect of drainage on the before state (upper figure); Figs. 5 (a) and (b) show a variation of the invention to solve a Type IV problem in a slope with a surface erosion problem. The slope has surface erosion and the water

table is less of a problem when compared with surface run-off. The two water tables are the same; Fig. 6 shows the functions of the components of the invention. The arrows show water seepage Fig. 7 shows a bio-bed 14 days after seeding (Left portion is Type I, central portion is Type II, right portion is Type III (ref. Table 3, Panel No. 1); Fig. 8 shows a bio-bed covered with growth bed prior to seeding-2 months (Left portion is Type IV, right portion is Type I (ref. Table 3, Panel No. 5)); Fig. 9 shows drainage pipes installed in the bio-beds (ref. Table 3, Panel No. 6-3); Fig. 10 shows bio-beds with pearlite and covered with growth bed (a) Second plot from left is Type VI, third plot from left is Type II (ref. Table 3, Panel No. 7) (b) Left plot is Type IV, right plot is Type VI (ref. Table 3, Panel No. 8-1); Fig. 11 shows growing conditions of the bio-beds tested (ref. Table 3, Panel No. 8-2 and 8-3); Fig. 12 shows the sprayed growth bed mix (ref. Table 3, Panel No. 9); Fig. 13 shows the drainage test setup; Fig. 14 shows the growing conditions: (a) 2-1, (b) 2-2 and (c) 2-3 (ref. Table 5. Panel No. 2-1.2-2 and 2-3) ; and Fig.. 15 (a) and (b) show roots penetrating the bio-beds.

DETAILED DESCRIPTION OF THE INVENTION The invention is a new type of environmentally friendly slope protection system, preferably based on a multi-layer concept. The biocrete system 10 preferably consists of 4 main layers: the bio-bed, the growth bed, the water barrier and the drainage layer.

However, one or more of these layers may be used in combination with conventional slope stabilization systems. A schematic diagram of the invention is shown in Figure 1 and 6. The invention preferably includes: Bio-bed 15-This layer is preferably made of concrete embedded with specially designed bio-capsules. The capsules are preferably shaped as round balls, but may be any suitable shape. The concrete forms the matrix/skeleton

of the layer. It provides the bio-bed with structural strength and surface erosion resistance. The bio-capsules packed with nutrients and seeds for vegetation growth are embedded in the concrete. The concrete and bio- capsules mix can be sprayed to slope surface by a dry or semi-dry spraying method that is useful for shotcreting. Upon drying, grass and other plants can be planted on top of the bio-bed.

Water barrier 20-this layer is preferably a mortar mix. It has very low permeability and is used as a water barrier to reduce water from the bio-bed infiltrating into slopes. The system may also include a drain 75.

Drainage layer 25-this layer is preferably a lean mix concrete with mainly uniform sand. It has very high porosity and permeability. It acts as a blanket drain intercepting all the seepage from slopes to prevent any buildup of pore water pressure in slopes.

Growth bed 30-this layer is preferably a soil mix packed with nutrients and seeds. It provides a growth environment for the seeds to germinate and grow.

Figure 1 also shows a water table 35 and a water bearing layer 40 The characteristics of the invention are as follows: a. it has high erosion resistance; b. it can sustain vegetation growth-enhance the appearance of slope features and improve air quality ; c. it can be applied to steep slopes; d. it is very cost effective; e. it is permeable-seepage from slope surface can be drained out readily; thus enhancing slope stability; f. it can also be applied to rock slopes or existing sprayed concrete protected slopes; and g. it can be used in soil conservation areas.

The invention is very flexible. Different components (or layers) of the invention can be combined to provide optimum solutions to specific site problems. We have identified four common areas where the invention can effectively improve slope

safety. They are: 1) newly formed slopes, 2) sprayed concrete covered slopes without drainage problems, 3) sprayed concrete covered slopes with drainage problems, and 4) vegetated slopes with surface erosion problems. The solutions to these problem areas are discussed below.

Type I-Newly formed slopes The preferred system used to protect slope surfaces is shown in Figure 2 (b). It preferably consists of 4 layers. The drainage layer acts as a blanket drain that intercepts seepage from the slope and discharge it to a sump that is tied to the city storm drain systems. The water barrier on top of the drainage layer prevents water from the bio-bed infiltrating into the slope. The bio-bed at the surface of the system provides a medium for vegetation growth and surface erosion protection. The growth bed provides a growth environment for seeds to germinate and grow.

Type II-Sprayed concrete covered slopes surface without drainage problem Sprayed concrete protected slopes have become an eyesore. Considerable efforts have been made to beautify the grey sprayed concrete surface by painting them green or brown. Figure 3 (a) shows a slope with an existing sprayed concrete surface 45. But with time, the colour fades and becomes unsightly.

Alternatively, a layer of bio-bed can be applied on top of the sprayed concrete surface (Figure 3 (b)) as if putting on a new coat. The bio-bed creates natural looking slopes. An additional benefit is the improved the air quality from the vegetation planted on the bio-bed.

Type III-Sprayed concrete covered slopes surface with drainage problem Seepage from slopes blocked by sprayed concrete usually manifests itself as wet spots on the sprayed concrete surface (Figure 4 (a)). When the weepholes on these slopes are blocked, groundwater pressure will buildup in the slope and cause rupture of the sprayed concrete cover and eventually failure of the slope.

This situation can be remediated by replacing a portion of or the entire sprayed concrete slope face with the biocrete. First, we remove the sprayed concrete cover and then apply a drainage layer (for example, 20-30 mm thick). A vegetated bio-bed on top of the drainage layer provides the finishing touch

(Figure 4 (b)).

Type IV-Vegetated slope with surface erosion problem In steep slopes, erosion of the surface (vegetated or not) occurs because of the high erosion force of surface runoffs and the weak binding strength between shallow grass roots and the surface soil (Figure 5 (a) shows an eroded area 50 and a vegetated surface 55). This type of slope face can be better protected by applying a layer of bio-bed 60 within which new grass or plants can be re- vegetated (Figure 5 (b)).

The invention can also be used for channel protection and soil conservation.

Phase 1-Development We developed a slope protection technique or product that provides both erosion protection and an environment for vegetation growth. A comparison of the functionalities of the various slope surface protection methods is listed in Table 1.

The invention provides a slope protection system with the following characteristics: a) erosion resistance; b) can sustain vegetation growth; c) can drain out seepage from slope surface; and d) cost effective.

The preferred embodiment of the invention, the biocrete system, consists of 4 layers (Figure 6). The functions of each layer are: 1. Bio-bed-to provide erosion protection and an environment for vegetation growth. It is preferably composed of concrete and other additives; 2. Growth bed-to provide a growth environment for seeds to germinate and grow.

3. Water barrier-to stop water from infiltrating into slopes; and 4. Drainage layer-to intercept and drain away seepage from slope surface.

The appropriate composition of the bio-bed mix is important. One skilled in the art will be able to adjust soil and fertilizer content in the capsules to facilitate grass

growth but without reducing the strength of the bio-bed for erosion protection. As well, aggregate sizes are preferably adjusted to prevent interference with permeability of the drainage layer caused by densifying following dry spraying.

The bio-capsules made of silty clay (the ASTM classification), nutrients, and grass seeds may be formed by hand with diameters ranging, for example, from 5mm to 30mm. The bio-capsules may be strengthened with a coating of water soluble gel.

The bio-capsules are preferably then air dried before use.

The concrete portion is preferably composed of sand (for example, with a diameter greater than 0.63mm), crushed stone (for example, with a diameter less than 10mm), and cement (for example, Portland cement).

Mixtures of concrete, bio-capsules, and additives were mixed and cast in wooden panels as listed in Table 2. The size and the grass growing condition are listed in Table 3. There are changes in pH values of the mixtures with time.

Conclusions 1. The pH values of the bio-bed mixes decrease with time. In general it decreases from an initial average value of 11 to 7.5 in 21 days. Since it will take more than 20 days for grass roots to penetrate the bio-bed the high initial alkalinity environment in the bio-bed will not interfere with grass growth.

2. Permeability of the bio-beds was determined with the setup shown in Figure 13.

Water drained out of the bio-bed panels readily. This result showed that flow channels exist in the bio-beds.

3. The bio-bed panels tested were cast in place by hand. The resulting density of the mix may be smaller than those cast by dry spraying method.

4. All bio-capsules embedded in the bio-beds were observed to be coated with cement coating.

5. The germination rates of the grass seeds embedded in the bio-capsules were low.

However, the bio-capsules design is usefully modified, as described below, so that grass seeds can grow rapidly in the bio-capsule.

6. It is preferable to embed grass seeds in a thin layer of growth bed on top of the bio- bed to facilitate seed germination. With time grass root will grow into the bio-bed.

7. The bio-capsules for this phase of the work were formed by hands. If large quantities of bio-capsules are required, they may be prepared with bio-capsule manufacturing methods described below.

Phase 2-Development of the bio-bed and the drainage layer 1) We dry sprayed the bio-bed and the drainage layer in order to show the optimum mixes for the bio-bed and the drainage layer, 2) We showed the feasibility and practicality of using dry spraying method to construct the bio-bed, the drainage layer, and the top soil layer, 3) We provided the preferred construction procedures for the construction of the bio- bed, and the drainage layer by dry spraying method, and 4) We modified the cement coating formed around the bio-capsules.

A 30m long 1. 5m high embankment was formed with slope gradient varies from 45° to 80° at the test site. A thin cement-sand layer was sprayed on the embankment surface forming-lm width panels. The different slope gradients of the panels simulated different field slope conditions. A 3 cm by 3 cm wire mesh was placed on the surface of each panel. Then, the bio-bed panels were sprayed using a ZP-VIII 5 m3/hr concrete spraying machine.

Testing Method Bio-capsules were formed with a turn-table. To crack cement coating formed on the surface of the bio-capsules, the bio-capsules were coated with a film of bentonite powder. Other suitable smectite clay minerals which absorb large quantities of water in proportion to their weight (and which expand) will be apparent to those skilled in the art. Upon wetting, the bentonite layer expands and cracks the cement coating such that grass roots can penetrate the bio-capsules. Examples of compositions of the bio- beds tested are listed in Table 4. The mixes show the effects of the compositions on the strength, and the suitability for vegetation growth (Table 5). To improve the channels between the bio-capsules in the bio-bed, various additives were added to the mixes. The additives added to each bio-bed panels are presented in Table 4. To reduce softening of the bio-capsules due to wetting during spraying, a soluble gel coating was applied to the bio-capsules.

The thickness of each bio-bed sprayed was approximately 30 mm. Other thicknesses may be used. After 2 days of curing, a geonet was placed on top of the bio-bed, and a layer of top-soil mixed with grass seeds and fertilizer was then sprayed on top of the bio-bed panels with the spraying machine used for the spraying of the bio-beds.

The bio-bed panels and the rate of grass growth show: 1. The bio-bed panels sprayed have a 28 days compressive strength ranging from 4.8MPa to 6.77 MPa (Table 5).

2. Spraying increases the density of the bio-bed and decreases the channels between bio-capsules.

3. Rebound during spraying increases with the amount of crushed stone used in the mix.

4. All 6 types of grass sprayed germinated and survived throughout the testing duration (Table 5).

5. Less than ten percent of grass roots extended pass the bio-bed due to a more favorable growing condition (both fertilizer and water) in the growth bed. The more ideal situation of more than 50% of the growth occur in the bio-bed can be achieved by embedding a drainage system in the bio-bed that supplies needed water and nutrients to the grass roots.

6. The bio-capsule composition is usefully modified to include organic fertilizer.

This improves the organic content of the bio-capsules. This facilitates grass roots penetration into the bio-bed.

7. The use of pearlite did not improve the environment for root penetration.

However, it increased the amount of rebound. Therefore it is optional to use pearlite in the bio-bed mix.

8. The amount of water used during spraying should be controlled to avoid formation of an impervious cement slurry.

9. Additives, such as rice husk, improve the connectivity between bio-capsules and increase the air void ratio of the bed.

10. The bentonite coating expands upon wetting and cracks the cement coating around the bio-capsules. One may use very dry bio-capsules instead of, or in

addition to, bentonite coated bio-capsules.

A panel was sprayed with a high porosity concrete mix. The composition of the drainage layer mix, No. 2-11, is presented in Table 4. The drainage layer is hydraulically isolated from the embankment surface with a plastic sheet. An impervious cement paste was applied on the surface of the drainage layer. Three plastic tubes were connected to the drainage layer. The top tubing was for the injection of water into the drainage layer to simulate seepage from slopes. The bottom tubing was used as a piezometer to measure the water level in the layer. The middle tubing was use as a drain. During a test the drainage layer was filled up with water using the top tubing, the water level in the drainage-layer was measured with the bottom tubing while the middle tubing was shutoff. When the water raised to the top of the drainage layer, the middle tubing was then turned open, and the rate of water level drop was measured by the bottom tubing. The effectiveness of the drainage layer was determined by the rate of water drop measured by the bottom tubing.

The results of the drainage test show that the panel is almost impervious. The drainage test was abandoned because the slow water intake rate of the drainage layer (4 hours of injection under a hydraulic head of 2m, the panel is still unsaturated).

The results show that dry spraying method densifie the drainage layer, and the loss of crushed stone due to rebound decreased the air void of the layer. These effects rendered the drainage layer impervious. To minimize rebound a mix with coarse sand and less crush stone is useful. Additives such as aluminum powder can be used to increase the air void ratio of the drainage layer.

We improved the strength and the air void ratio and reduced the amount of rebound of the bio-capsules by reducing the size of the bio-capsule to 5 mm diameter.

Twenty percent of organic fertilizer was added to the bio-capsules in order to increase its organic content. With these modifications, new bio-bed mix designs were established. The compositions of the twelve mixes are listed in Table 6. Mix No. 3- 17 with 120g of aluminum powder was also prepared. All tests proceeded with a thin layer of top soil with grass seeds and fertilizer sprayed on top of the panels and then left to cure for two days. CMC gel (carboxymethyl cellulose) is optionally added to

the growth bed mix to improve its erosion resistance. Other additives may optionally be used with the invention, for example, to increase the concrete's workability, setting time and/or strength. Any suitable aggregate may also be added to the concrete.

Typically concrete is made from three sizes of particles: cement (siltsize), sand and aggregate. Thus aggregate, which typically comprised about 40% by volume (70% by weight) refers to, for example, crushed stone or river gravels composed of rock forming minerals, ie rock fragments, which are larger than sand size.

Results Observations one week after the seeding indicated that the bonding between the bio-capsules had been improved drastically. The 28 days compressive strengths of the beds ranged from 4.5 to 7.2 MPa. The modified bio-bed provided a very favorable medium for grass root penetration (Figure 15). To speed up grass growth, a green house environment was created for all the panels.

The composition of the drainage layer mixes, No. 3-14 and 3-22, is shown in Table 6. With an effort to increase the permeability of the mix, the sand portion was limited to a size greater than 2.5 mm by passing the sand particles through a set of sieves; the smaller sand grains were discarded. The amount of crushed stone was also reduced. Furthermore, the mix consisted of about 8 kg of rice husk.

Results The new mixes had 28 days compressive strengths ranging from 3.6 to 4.3 MPa.

Initial field observations indicated that the drainage layers were very pervious.

Laboratory permeability tests on samples are being conducted to determine the permeability of the layer.

We apply the invention to a slope with approximately 70° gradient. The slope is fully monitored with piezometers. The rate of grass growth is monitored daily. When the grass is fully grown water sprinklers simulate heavy rainfall conditions to show the erosion resistance of the system. Seepage from the slope is simulated by a pre- installed under-drain system to show the effectiveness of the drainage layer.

The invention provides a working version of the bio-bed mix and drainage layer mix for slope greening and stabilization.

With the use of coarse sand in the drainage layer we expect the cost to be about

5% higher than sprayed concrete.

The dry spraying technique used for the construction of sprayed concrete is useful for the construction of the bio-bed and the drainage layer in slopes with a gradient up to 80° with about 20 to 25% of rebound loss. One skilled in the art will control the amount of water used during spraying to prevent a layer of cement slurry on the surface of the bio-bed.

The present invention has been described in detail and with particular reference to the preferred embodiments; however, it will be understood by one having ordinary skill in the art that changes can be made thereto without departing from the spirit and scope of the invention.

All articles, patents and other documents described in this application are incorporated by reference in their entirety to the same extent as if each individual publication, patent or document was specifically and individually indicated to be incorporated by reference in its entirety. They are also incorporated to the extent that they supplement, explain, provide a background for, or teach methodology, techniques and/or compositions employed herein. Slope angle Vegetation Sprayed* Biocrete concrete <45° yes Yes Yes Soil slope >45° No Yes Yes <45° No Yes Yes Rock slope >45° No Yes Yes *with aesthetic problem<BR> Table 1 A Comparison of the Applicability of the 3 Types of Slope Protection Systems Table 2 The Bio-bed Mixes Mixes, kg Crush stone No. cement Sand >0.63mm Bio-capsules Other additives Water (<10mm) A 1 1.7 1.7 1.4 1.0 Composite fertilizer B 1 3 1.2 0.9 0.05 C 1 0.84 1.7 1.4 1.0 D 1 0.84 1.7 1.4 Shredded straw 0.17 1.0 E 1 1.7 1.4 Shredded straw 0.17 1.0 F 1 0.43 1.7 1.4 Shredded straw 0.17 1.0 G 1 1.75 1.75 1.0 Shredded straw 0.17 0.9 H 1 1.75 1.75 1.0 Pearlite0.2 1.0 I 1 1.55 1.55 1.0 Shredded straw 0.17 1.0 J 1 1.5 1.5 1.0 Shredded straw 0.17 1.0 Table 3 Dimensions of the Bio-bed Panels and the Grass Growing Conditions (sheet 1 of 2) Bio-bed@panels Bio-bid No. mix- Dimensions Remarks Seeding method Type of grass Grass growin conditions Remarks ref. cm Table 2 3, 7, 14 days cured panels 1 A 18X28X4 sed on surface, covered with Type I, II, III 14 days germinated - rate 10% Figure 7 shredded straw No 2 B 14X28X3 Seed embedded in Bio-capsules After 12 days no germination germination Cover panel with 1cm soil, added 7 days Type I, II, III and VI 3 A 30X40X3 6 panels 4 g seed and 2 g fertilizer, than Type I to VI 20-40% grass cover with shredded straw IV and V not as good Push Bio-capsules with seed into Type I, II and 12 days 5% germinated, 4 A 30X40X3 5 panels bio-bed then protected with cloth IV to VI 10 days brown Become yellow Seeds on top of 1cm soil than 3 days germinated 7 dyas 40- 5 C 14X28X3 Type I and IV because of 0.5cm soil on top 805 grass 14 days 90% grass over heat Figure 8 Germination With 1cm soil. 1/2 panel with seed and 5 days germinated, 14 days fast outside 6-1 D 14X28X3 shredded 1/2 panel with Bio-capsule with Type II and IV straw seed embeeded. Then 0.5cm soil 90% gras of the Bio- capsules 1cm soil. 1/2 panel with seed With Seed and 1/2 panel with Bio-capsule 5 days germinated, 14 days 6-2 E 14X28X3 shredded Type I and VI germinated in with seed embedded 100% grass straw soil only then 0.5cm soil With 1cm soil. 1/2 panel with seed and 5 days germinated, 20 days 6-3 F 14X28X3 shredded 1/2 panel with Bio-capsule with Type III and V for seeds embedded in the Figure 9 straw seed embedded then 0.5cm soil bio-capsules With 1 day cur. 45° 7 G 60X40X5 shredded 0.5 cm soil then added 20-40g/m2 Type II, V, vI Same as 5 Figure 10 straw of seeds With 5 days germinated, 10 days 8-1 H 14X28X4 pearlite Soil mixed with 2g of seeds Type VI Figure 10 stone 60% grass 3-4cm tall With 5 days germinated, 10 days 8-2 I 14X28X4 pearlite Soil mixed with 2g of seeds Type II, V Figure 11 stone 70% grass 3-4 cm tall With 5 days germinated, 10 days 8-3 J 14X28X4 pearlite Soil mixed with 1g of seeds Type IV Figure 11 stone 40% grass Dry spray soil with cocnut 7 days germinated 12 days 9 G 100X100X4 4 panels Type II, IV to VI figure 12 shredded and seeds 50% grass Table 3 Dimensions of the Bio-bed Panels and the Grass Growing Conditions (sheet 2 of 2) Mix in kg NO. Casting Date Dimension cm slope cement silica furrie Curing agent sand stone bio-capsule additives remarks 2-1 1999/9/27 160#200#8 35° 50 0 2 87.5 87.5 50 rbound 5-10% 2-2 1999/9/29 100#20034 35° 50 0 2 25 150 75 rebound 15% 203 199/10/7 100#20#4 35° 50 0 2 50 125 60 rebound 5-10% 2-4 199/10/8 100#200#4 35° 50 0 2 50 150 75 rebound 15% 2-5 199/10/14 100#200#4 42° 50 0 2 50 150 75 rebound 15% 2-6 1999/11/2 100#160#4 35° 60 0 3 50 135 75 rebound 5-10% 2-7 1999/10/25 100#160#4 70° 65 0 3 50 15 60 rebound 15-20% 2-8 1999/10/30 200#160#4 70° 120 0 6 75 300 150 rebound 15-25% 2-9 1999/11/13 200#160#5 70° 120 8 6 120 250 150 rebound 15-25% 2-10 1999/11/16 100#160#5 70° 60 4 3 25 150 150 pearlite 5 rebound 15-20% 2-11 1999/11/71 100#160#5 70° 60 0 3 160 150 0 rebound 15-25% Table 4 The Ddimnsions and Mixes of the Bio-bed Panels Formed by Dry Spraying Method 28 days Compressive NO. Casting Date Seeding Date Top-soil mix Seed Type Growing Condition Remark strength MPa 2-1 1999/9/27 6.0 1999/10/13 soil + fertilizer + husk Type VI 40g 3 weeks 50% grass, 1cm tall Figure 14 2-2 1999/9/20 5.4 1999/10/13 soil + fertilizer + husk Type II 40g 3 weeks 50% grass, 1cm tall Figure 14 2-3 1999/10/7 4.8 1999/10/13 soil + fertilizer + husk Type V 40g 2 weeks 50% grass, 1-1.5cm tall Figure 14 2-4 1999/10/8 4.8 1999/10/13 soil + fertilizer + husk Type IV 30g 2 weeks 50% grass, 0.5cm tall 2-5 1999/10/14 4.8 1999/10/28 soil + fertilizer + husk Type IV 40g 2 weeks 10% grass, 0.5cm tall 2-6 1999/11/2 5.0 1999/11/4 soil + fertilizer + husk Type VI 40g 1 week seed germinated 2-7 1999/10/25 5.1 1999/10/30 soil + fertilizer + husk Type VI 30g 2weeks 50% grass, 0.5cm tall 2-8 1999/10/30 5.5 1999/11/2 soil + fertilizer + husk Type II 80g 1 week germinated 2-9 1999/11/13 6.3 1999/11/16 soil + fertilizer + husk Type IV 40g 2 weeks 60% grass, 1cm tall 2-10 1999/11/16 6.7 1999/12/3 soil + fertilizer + husk Type I root 5d grass become green 2-11 1999/11/16 4.0 drainage layer impervious Table 5 Performance of the Bio-bed Panels Formed by Dry Spraying method Mix in kg slope No. angle silica curing bio- cement sand crush stone additives remarks fume agent capsules 3--11 70° 50 3. 2.5 25 150 55 3--12 70° 60 4 3 25 150 55 pearlite 15 3--13 70° 50 3.3 2.5 25 150 65 rice 10 (>2.5mm) 3--14 70° 60 3 rice hush 8 drainage layer 240 3--15 70° 50 3.5 2 75 100 70(fert) rice hush 10 3--16 70° 60 5 2.6 75 100 70(fert) rice hush 8 3--17 70° 120 10 5.2 150 200 120(fert) rice hush 12 added 120g aluminium powder 3--18 70° 150 2.6 170 220 120 20 rice husk 3--19 70° 186 15 8.1 254 338 120(fert) rice hush 27 3--20 70° 60 5 2.6 75 100 65 rice hush 15 rice hush 5 rice 3--21 70° 60 60 110 50(fert) 10 (>2.5mm) rice hush 5 rice 3--22 70° 60 3 110 45 drainage laye 60 10 3--23 73° 63 5 3 100 80 50(fert) rice hush 10 k=4x10-5 cm/s 3--24 77° 60 5 3 80 100 50(fert) rich hush 8 Table 6 The Dimension and Mixes of the Bio-bed Panels Formed by Dry Spraying Method