Field of the disclosure

The disclosure relates to the field of water storage.

Background

It is known to provide attenuation tanks to store water under the ground. The tanks may be used simply to store water for later redistribution, or may be used to store excess water such as that caused by water run off after rain. The tanks are able to control the flow of stored water being pumped into watercourses, reducing the risks of floods.

Attenuation tanks and other water stores are often located in excavated sections of soil. Conventionally, an attenuation tank is either waterproof in and of itself, or is placed on a waterproof membrane to prevent leakages. Placing the tank or water store on a waterproof membrane may prevent water losses to the soil. The membrane may be damaged by the tank, or may have a shorter lifespan than the tank. Using a plastic membrane may result in microplastics or plastic particles entering the soil. Furthermore, a plastic membrane is unlikely to provide a stable base for the tank in the event of soil shifting or subsiding. Substances such as asphalt or cement may help with stability, but require transport of bulky aggregates and are time-consuming to apply. Without a solid sub-bed, asphalt or cement layers may be prone to deformation in the event of soil shrinkage or swelling.

Summary of the disclosure

Against this background, there is provided a subterranean water store, the subterranean water store comprising a basin configured to store water, the basin provided below ground level, wherein a base of the basin comprises consolidated soil configured to be loadbearing and to be resistant to water penetration. The subterranean water store further comprises a framework provided in the basin, wherein the framework is configured to define a volume for storing water and support a ground layer above the volume.

In this way, it is possible to provide a load-bearing and waterproof base for a water storage reservoir by treating the existing soil. Using consolidated soil as the base avoids adding any contaminating substances to the soil (such as plastics) and reduces the use of cement. In-situ materials are utilised, avoiding the need to transport heavy or bulky aggregates. In some embodiments, water store may be used simply to store excess water or run-off and to direct the water to a water course or drain. In some embodiments, the water store is provided below a field for agricultural applications. The water store may be used to feed an irrigation system, which may be used to water crops in a field above the water store. The water store may be used as a flood defence by storing floodwater and releasing it in a controlled manner.

Brief description of the drawings

A specific embodiment of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a schematic diagram of a cross-section of a water store in accordance with an embodiment of the present disclosure.

Figure 2 shows a schematic diagram of a cross-section of a water store in accordance with an embodiment of the present disclosure.

Figure 3 shows a schematic diagram of a cross-section of a water store comprising a water permeable membrane in accordance with an embodiment of the present disclosure.

Figure 4 shows a schematic diagram of a cross-section of a water store comprising an inlet in accordance with an embodiment of the present disclosure.

Figure 5 shows a schematic diagram of a cross-section of a water store comprising an irrigation system in accordance with an embodiment of the present disclosure. Figure 6 shows a schematic diagram of a cross-section of a water store comprising an overflow outlet in accordance with an embodiment of the present disclosure.

Figure 7 shows a schematic diagram of a cross-section of a water store in accordance with an embodiment of the present disclosure.

Detailed description

A subterranean water store in accordance with an embodiment of the present disclosure comprises a basin configured to store water. The basin is provided below ground level. A base of the basin comprises consolidated soil configured to be load-bearing and to be resistant to water penetration. A framework is provided in the basin, wherein the framework is configured to define a volume for storing water and to support a ground layer above the volume.

Figure 1 shows a simple schematic diagram of a cross-section of a subterranean water store 100. As shown in Fig. 1 , the base 111 of the basin 111 is a generally flat portion of the basin 110 on which the framework 120 is provided. The base 111 prevents water loss to the soil below the framework. The basin 110 may further comprise one or more raised portions 112, 113 which surround the base 111 to define a volume of the basin. As such, raised portions 112 and 113 are configured to provide a barrier adjacent to the sides of the framework 120. The raised portions 112, 113 may be configured to prevent lateral or horizontal water loss from the basin. There may be a gap between the raised portions of the base and the sides of the framework 120. That is to say, the framework 120 may not completely fill the volume defined by the basin 110. The basin 110 may comprise a raised portion 112 on each side of the framework, such that the basin retains water in all lateral directions. The ground layer 130 is supported by the framework 120, and may also be supported by the basel 10.

The base 111 of the basin 110 comprises consolidated soil. With reference to Figure 2, the basin 110 of the subterranean water store 200 may comprise the base 111 (comprising a layer of consolidated soil, indicated by hatching) above non-consolidated soil (indicated by dots). The ground layer 130 may be the same as or different from the non-consolidated soil. Both are indicated by dots to differentiate them from the consolidated soil. The layer of consolidated soil may be formed from existing soil in the ground. The ground may be excavated to provide a recess in the ground of approximately the shape of the base 111 of the basin 110. The top layer of soil in the recess may then be treated in situ to form consolidated soil, such that the basin comprises a layer of consolidated soil covering the existing soil. The ground layer 130 or other non-consolidated substance may fill a gap between the base of the basin 110 and the framework 120.

The consolidated soil may comprise an agglomeration substance, wherein the agglomeration substance is configured to bind soil particles and to disrupt water films. The agglomeration substance may be hydrophobic. The agglomeration substance may be configured to disrupt water films of the soil particles in a mixture of soil and the agglomeration substance. The agglomeration substance may be configured to bind the soil particles in a compacted mixture of soil and the agglomeration substance. The agglomeration substance may comprise a powder and/or a liquid. For example, the agglomeration substance may comprise an agglomeration liquid and a consolidation powder, which may be mixed separately with the soil. The consolidation powder and method of forming consolidated soil is discussed in more detail below.

The subterranean water store 100 may comprise a filter configured to filter the water received by the support structure.

The framework 120 may comprise a crate or other support structure. The framework 120 may be configured to allow water to flow through the framework 120 and through the sides, top and bottom of the framework 120. The framework 120 defines a volume for storing water. In particular, the framework provides a support structure for the ground layer 130 above, such that the ground layer 130 does not impinge on the volume for storing water defined by the framework. The framework 120 may be configured to receive water via at least one of the top and sides of the framework 120. The base 111 of the basin 110 may be configured to enclose a lower portion of the framework 120. The lower portion may comprise at least the bottom surface of the framework 120. The framework 120 may be configured to receive water passing down through the ground layer 130, as indicated by the arrows

The framework 120 may, in a specific example, comprise modular crate units. The modular crate units may comprise load-bearing interlocking units. The framework 120 may have a high top surface area relative to its depth. For example, the framework 120 may have a depth of the order of 10 cm, and a top surface with dimensions of the order of 1 to 10 m. In a specific example, the framework may have a depth of 400 mm and a top surface of 10 m by 3m. the ground layer may have a depth of between 350 mm and 500mm, and the basin may have a layer of consolidated soil with a depth of 250 mm. The framework 120 may comprise modular open crates or rafts, with high compressive strength and a high percentage of the unit volume being a void. The framework 120 may comprise polypropylene. In a specific example, the framework 120 may comprise Permavoid units. In another specific example, the framework 120 may comprise a Polystorm Geocellular System. In embodiments, the framework 120 comprises cells having a high void ratio, preferably 90 % or above, and more preferably 95 % or above. In embodiments, the framework may have a load bearing capacity of between 20 and 83 tonnes per square metre. In embodiments, the framework 120 is configured to allow water flow through the framework 120 in three dimensions. The framework 120 may comprise capillary cells to transport water upwards through the framework via capillary action.

Figure 3 illustrates an embodiment of a subterranean water store 300 where the top and sides of the framework are enclosed by a water permeable membrane (indicated by dashed line 310), and raised portions 112, 113 of the basin 110 provide a barrier adjacent to the sides of the framework 120. The barrier may be configured to be resistant to water penetration. A water permeable membrane 310 (see Fig. 3) may be configured to enclose an upper portion of the framework 120. The upper portion may comprise at least the top surface of the framework 120. The upper portion may further comprise at least part of the sides of the framework 120. The framework may be configured to receive water through the water permeable membrane, and the water permeable membrane may be configured to filter the received water. Water received through the water permeable membrane may pass through the ground layer 130. For example, rain may fall on the ground layer 130 and pass through the ground to reach the framework via the water permeable membrane. Water may leave the framework via the water permeable membrane. Water leaving the framework via the water permeable membrane may be retained within the basin. In an embodiment, the sides of the framework 120 may comprise an aggregate configured to store water.

The water permeable membrane 130 may comprise any membrane configured to be permeable to water and to filter soil or large particles from the water. In a specific example, the water permeable membrane 130 may comprise a geotextile comprising polyester fibres. In addition to being permeable to water, the water permeable membrane may have wicking properties and may be configured to transport water laterally across the membrane.

With reference to Figure 4, the framework 120 of a subterranean water store 400 may be configured to receive water via an inlet 410. The framework may be configured to receive water via the inlet 410 in addition to or instead of via the top and/or sides of the framework 120. The inlet 410 may be configured to receive water from a natural water source, such as a watercourse, or from collected rainwater. The inlet 410 may be configured to receive water from a mains supply. The water store may comprise a filter configured to filter water received via the inlet 410. As such, in some embodiments, the subterranean water store 100 may collect water which has permeated through the ground layer 130 above, and/or from water supplied via the inlet 410.

In an embodiment, with reference to Figure 5, the subterranean water store 500 may comprise a first outlet 510 configured to receive water from the framework 120 and direct the water to an irrigation system 520. That is to say, the first outlet 510 is connected to the volume for storing water defined by the framework 120. The irrigation system 520 may be configured to provide water to crops in the ground layer 130 above. In use, any excess water in the ground layer 130 from the irrigation system 520 or rainfall may pass downwards though the ground layer 130 and be received by the framework 120. In an embodiment, the subterranean water store 100 may comprise a pump 530, wherein the pump 530 is configured to pump water from the framework 120 to the irrigation system 520 via a pipe from the first outlet 510. In an embodiment with or without an irrigation system, the pump 530 may be further configured to pump water from the framework 120 to a watercourse or drain, or to pump water from a watercourse into the framework 120. In another embodiment, the water may be provided to the irrigation system passively, for example via capillary action.

In an embodiment, with reference to Figure 6, the subterranean water store 600 may comprise an overflow outlet 610. The overflow outlet 610 may be configured to receive water stored in the framework 120 in an event that the water level 620 in the framework 120 exceeds an overflow threshold level, until the water level 620 is below the overflow threshold level. The overflow outlet 620 may direct water to a watercourse or drain via a pipe. The overflow pipe may release water in a controlled manner. In an embodiment, the subterranean water store 100 may comprise a controller configured to monitor one or more of a weather forecast and a water level in the framework 120. The controller may be configured to control the pump. The controller may be configured to control the pump based on one or more of the weather forecast and the water level in the framework 120. The controller may be configured to control the irrigation system. .

In an embodiment, the controller may be configured to monitor a water level in the framework. For example, the controller may monitor a water level in the framework 120 over a period of time where a change in the water level in the framework 120 is not expected. For example, the period of time may be a period where no rainfall has occurred in the preceding 24 hours. The controller may monitor the water level in the framework 120 over the period of time in order to determine a change in the water level over the time period. The controller may subsequently determine a water usage rate based on the change in water level over the time period.

In embodiments, an outlet of the subterranean water store 100 directs water to an irrigation system (as shown in the example in Figure 5). The controller may be configured to monitor moisture levels of the ground layer above the framework 120.

The subterranean water store 100 may comprise one or more sensors, or may be connected to one or more sensors. One or more sensors may be connected to an alarm, wherein the alarm is configured to notify an operator in the event that the sensor measurement deviates from a pre-determined range. One or more sensors may be configured monitor properties of the subterranean water store 100 such as a water level within the framework 120, leaks from any part of the subterranean water store 100, water flow through any part of the subterranean water store, or other properties. One or more sensors may be configured to detect leaks through the basin 100 around any component of the subterranean water store 100 that passes through the basin 110 (for example, any leaks around a pipe passing through the basin 110). One or more sensors may be configured to monitor properties of the environment around the subterranean water store 100, such as water content in the soil of the ground layer 130. One or more sensors may comprise a soil moisture sensor, such as a neutron soil moisture sensor, a tensiometer, or a dielectric soil moisture sensor. A neutron soil moisture produces fast neutrons, which lose energy on collision with hydrogen nuclei. The degree of attenuation of the neutrons may be used to determine the quantity of hydrogen, and therefore of water, in the soil. A dielectric sensor measures the dielectric constant of the soil, which increases with moisture content of the soil. The dielectric sensor may comprise a capacitive sensor, with a capacitance proportional to the dielectric constant of the material being measured. A tensiometer soil moisture sensor may comprise a porous head (for example a porous porcelain head) connected to a vacuum gauge through a pipe filled with water. Capillary action transports water into the soil, resulting in a negative pressure in the closed pipe, which can be related to the moisture content of the soil. Data collection from one or more sensors may be wireless. For example, the one or more sensors may be configured to transmit sensor data over a wireless network to a remote server or a remote application running on a remote device. The wireless network may be a radio access network such as a cellular network or a WiFi (RTM) network.

In certain embodiments, one or more sensor modules may be provided in the soil. One or more sensor modules provided in the soil may comprise a soil moisture sensor, or other type of sensor configured to monitor properties of the soil or environment around the subterranean water store. One or more sensor modules provided in the soil may comprise a wireless power source, such as a battery. One or more sensor modules provided in the soil may wirelessly send data collected by the sensor module to a controller, server or other location. In certain embodiments, a plurality of sensor modules may be provided in the soil. For example, an array of sensor modules may be provided. The sensor modules may be wireless.

The water store may further comprise a solar power source. The solar power source may be configured to power at least one of a pump, a filter and a controller. The solar power source may be configured to provide power to the grid. The water store may comprise a different energy source, such as a wind turbine.

The water store may comprise any combination of the features described above.

Figure 7 illustrates an example of a subterranean water store 700 in use. Water may enter a chamber 2 via an inlet 1 . The chamber 2 may comprise a value chamber, meter and actuator. The water may then pass via a filter pump level sensor 3 to a filtered inlet 4, wherein the framework 5 is configured to receive water via the filtered inlet 4. The framework 5 is supported on the base 6 of a basin 61 . An overflow pipe 7 receives water over a threshold level in the framework 5. The water permeable membrane 8 filters water that is received through the top and sides of the framework 5 (indicated by vertical arrows from the top of the ground layer). Solar panels 9 are configured to provide system and utility power. A control panel 10 comprises a weather station and cloud monitoring. The control panel is configured to drain the framework 5 in an event that rain is expected. The irrigation system and drip line 11 feeds water from the framework to crops in the ground layer above the framework. Any excess water (and any residual fertiliser in the ground layer) will return to the framework 5 through the soil.

A method of installing the subterranean water store may comprise excavating a volume of soil from the ground, forming a recess of the approximate shape of the basin. As described above, the basin may comprise a flat base. In other embodiments, the basin may comprise a curved base and raised portions or may comprise graded, flat sides that define a basin volume. The basin may comprise a flat base and curved raised portions, or the basin may comprise a flat base and graded, flat raised portions. The basin may have a width that is substantially larger than its depth. In an embodiment, the depth of the basin (from the top of the raised portion to the top surface of the base) may be of the order of 100 or 1000 mm. For example, the depth of the basin may be between 50 cm and 2 m. The thickness of the basin may be of the order of 100 mm. The width of the basin may be of the order of 1 to 10 m, or larger. In an embodiment, the width of the basin may be similar to the width of a field.

In an embodiment, the soil in the recess is treated in situ to form the consolidated soil of the base.

In an embodiment, treating the soil comprises mixing an agglomeration substance with the soil, and then mechanically compacting the mixture of the soil and the agglomeration substance. In an embodiment, the agglomeration substance comprises more than one substance, wherein each substance may be separately mixed with the soil. For example, the agglomeration substance may comprise an agglomeration liquid and a consolidation powder.

In an embodiment, a method of treating the soil comprises mixing or blending the soil to be consolidated with an agglomeration liquid followed by a consolidation powder. The liquid and solid powder formulations provide ground stabilisation when mixed with the soil and included components that act catalytically to disrupt adhering moisture films within the soil. The method may provide soil stabilisation, enhanced compaction and moisture absorption resistance through augmented petrification (either partial or near complete petrification), wherein the enhanced compaction provides a significantly increased California Bearing Ratio (CBR). The agglomeration liquid may comprise both aqueous and organic components and is configured to disrupt adhering water films present within the in-situ soil whilst also inducing an irreversible agglomeration of fines (particle fractions more than 0.075 mm) to reduce capillary rise of water. The agglomeration liquid improves compaction of the in-situ soil to higher densities and is a non-binding catalytic formulation to improve soil characteristics through the conglomeration effect. The agglomeration liquid may comprise water, an aminoalkyl compound, an alkylammonium chloride and a solvent. The consolidation powder may provide a binding function. The consolidation powder may comprise a lime containing compound and a carrier material. The consolidation powder may comprise an alkylammonium chloride, a supplementary cementitious material and a lime containing material. Alternatively, pulverised fly ash (PFA) may be used a consolidation powder. In certain embodiments, the consolidation powder may comprise PFA without lime or cement.

Soil that has been treated using the agglomeration liquid and a consolidation powder has a high California Bearing Ratio (CBR) and has low carbon emissions associated with its production and its use in a construction process. Although the present disclosure does not relate to roads, these benefits may be demonstrated by a comparison to typical haul roads and to asphalt roads. Soil that has been treated using the agglomeration liquid and a consolidation powder has an significantly increased CBR when compared to typical haul roads or asphalt roads. Furthermore, constructing roads using soil that has been treated using the agglomeration liquid and a consolidation powder significantly reduces carbon emissions associated with the production of the material and its use in construction, when compared to a typical haul road or asphalt road. Where a consolidation powder comprises an alkylammonium chloride, a supplementary cementitious material and a lime containing material, the carbon savings may be in the region of 47% to 67% compared to a standard haul road and 83% to 88% compared to an asphalt road. The carbon savings may be increased by using a consolidation powder comprising PFA without lime or cement.

In some embodiments, the consolidated soil defines a load-bearing layer of a first thickness. Treating the soil may comprise mixing an agglomeration substance with the soil to a depth equal to the first thickness, and then mechanically compacting the mixture of soil and the agglomeration substance. Treating the soil may comprise a step of mixing an agglomeration liquid with the soil to a depth equal to the first thickness and a step of mixing a consolidation powder with the soil to a depth equal to or less than the first thickness. The method may then comprise mechanically compacting the soil after the steps of mixing the agglomeration liquid and the consolidation powder with the soil.

In an embodiment, the method of treating the soil may comprise determining various properties of the soil prior to mixing the agglomeration substance with the soil. For example, the method may comprise determining a composition of the soil to be consolidated to form the layer. Components within the soil may be identified, including any one or a combination of clay, sand, silt, gravel, stones and rock. The composition of the soil is then compared with a reference composition. Optionally, composition of the soil may be adjusted towards the reference composition by adding to the soil any one or a combination of clay, sand, gravel, stones and rock. Other properties that may be determined include a particle size of any one or a combination of the clay, sand, silt, gravel, stones and rock; a moisture content of the soil; a density of the soil; a liquid and/or plastic limit of the soil; a California Bearing Ratio of the soil; a permeability of the soil; a capillary rise of water by the soil; a compressive strength of the soil; the Atterberg limit of the soil; a linear shrinkage of the soil; a water penetration of the soil; a pH of the soil.

The framework may be deposited on the base, and a ground layer laid on the framework.

The consolidated soil and method of forming the consolidated soil may comprise, but not be limited to, the soil and method described in patent application GB2116977.6, the contents of which is incorporated by reference.