A method for producing and using an engineered fill.

Abstract

A method 100 for preparing and using an engineered soil fill for earthworks on a site is described. The method comprising the steps of: determining a geographical region on the site, and dividing the

Description

Field of the invention This invention relates to a method for preparing and using an engineered soil fill for earthworks, particular for the use in building foundations, ground floor slabs and external construction hardstanding areas. Introduction and background Many of the UK construction developments are built on site with pre-existing topsoil. Due to its poor engineering properties, it is not permitted by Engineers to re-use the topsoil as engineered fill within the earthworks. Therefore, excess topsoil that cannot be used in the landscaping areas is often deposited offsite. This creates additional heavy goods vehicle (HGV) movement and unnecessary costs, which in turn leads to further CO2 emissions and an increase in congestion of the road network. In civil engineering, "fill" refers to the process of placing and compacting earth materials, such as soil, rock, or other materials, in a controlled manner to create a stable and level surface. This process is commonly used to raise the ground level or support structures like roads, embankments, and buildings. Types of Fill Materials: The choice of fill material depends on the specific project requirements and site conditions. Some common types of fill materials include: Natural Soil: Natural soil from the construction site is often used as fill material after proper testing and modification to ensure it meets the project's engineering specifications. Granular Fill: This type of fill consists of well-graded, coarse-grained materials such as sand and gravel. Granular fill is used when good drainage and stability are essential. This type of fill will be used when this is the material available at the site. Cohesive Fill: Cohesive fill materials like clay and silt have fine particles that stick together, making them suitable for projects that require high water retention or impermeability. This type of fill will be used when this is the material available at the site. Engineered Fill: In some cases, it is necessary to import specialized engineered fill materials to meet specific project requirements, such as high compaction or stability. Made Ground: this is a type of fill such as colliery spoil, aggregate subbase or other material that has been changes in some form due to human activity. This material needs to be treated to be reusable. Importance of Engineering Fill: Foundation Support: Fill materials provide the necessary support for foundations and structures. A properly compacted fill ensures that buildings and infrastructure remain stable over time. Slope Stability: Engineering fill is used to create stable embankments and slopes. Slope failure can result in catastrophic consequences, so it is important to understand the properties of the fill material and how it interacts with the surrounding environment. Land Reclamation: Fill materials are used extensively in land reclamation projects, where land is created or expanded by adding suitable fill material to coastal or marshy areas. Road Construction: Roads often require extensive fill to level the terrain and provide a stable base for pavement layers. Properly engineered fill materials are essential for road longevity. Challenges in Engineering Fill: Working with engineering fill presents various challenges, including: Compaction: Achieving the required compaction density is crucial to ensure the stability and loadbearing capacity of fill materials. Settlement: Over time, fill materials may settle, leading to uneven surfaces and structural problems if not managed properly. Environmental Considerations: The choice of fill material must consider environmental impacts, such as groundwater contamination and habitat disruption. Quality Control and Testing: To ensure the success of a project involving engineering fill, rigorous quality control and testing procedures are essential. This may include: Compaction Testing: Regular testing to confirm that the fill material has been adequately compacted to meet project specifications. Soil Testing: Determining the properties of the fill material, including its particle size distribution, plasticity, and shear strength. Monitoring: Continuous monitoring of settlement and stability during and after construction to identify and address any issues promptly. If the site also requires levels to be lifted, then additional importation of suitable engineered fill material would be required to balance the volume of imported topsoil from site. Again, increasing HGV movement, CO2 emissions and costs. Topsoil or organic soils often fail to be suitable engineering fill due to theirorganic content. Engineers will often limit the organic content within their Earthworks Specification. Generally, the organic content of engineered fill is limited to less than 2% organic matter content. This proposed patent aims to re-use suitable topsoil within the engineered fill by blending it with other suitable soils with a lower organic content to provide a blended engineered fill with an organic content that is lower than specified in the earthwork's specification. Summary of the Invention According to an embodiment of the invention there is provided a method for preparing and using an engineered soil fill for earthworks on a site comprising the steps of determining a geographical region on the site, and dividing the geographical region into an upper topsoil layer, a lower topsoil layer and a subsoil layer, and at least one subsequent layer where each subsequent layer will have a % total organic matter content, TOMC; testing one or more layers layer, using chemical analysis to determine total organic matter content, TOMC, of one or more of the upper, lower and subsoil levels; removing the upper topsoil layer to a predetermined first depth from the top of the upper topsoil layer, blending the lower topsoil layer and the subsoil layer to a specified second depth from the top of the lower topsoil layer to produce a blended fill layer with an TOMC determined as having a TOMC value between a first TOMC value for the original lower topsoil layer and a second TOMC value for the subsoil layer; determining the TOMC of the blended fill layer; when the TOMC of the blended fill layer is no greater than 2% performing one or more geotechnical tests on the blended fill layer to determine whether the blended fill layer satisfies one or more target requirements of an engineering fill for the earthworks; if the one or more target requirements are satisfied, using the blended fill layer either in situ as engineering fill, or excavating the blended fill layer for use as engineered fill in an alternative location on the site; compacting and / or stabilizing the engineered fill in situ or in the alternative location; and testing the compacted and / or stabilized fill for compliance with the one or more target requirements for the site.. Preferably, the specified depth is at least 400mm. In a preferred embodiment of the invention each subsequent layer will have a smaller % total organic matter content, TOMC, than the preceding layer. In a preferred embodiment of the invention the lower topsoil layer and the subsoil layer are blended by rotavation. Further preferably, the one or more geotechnical tests comprise one or more of the following: Atterberg limit; particle size distribution, moisture content, moisture condition value and calibration; particle density and compaction, Californian bearing ratio, swell test. Preferably, the testing of the compacted and stabilized fill comprises one or more of the following tests: moisture content; moisture condition value and calibration; particle density and compaction, Californian bearing ratio, swell test, and unconfined compressive strength. In a preferred embodiment of the invention, removing the upper topsoil layer to a predetermined depth removes topsoil, and any roots or waste matter from vegetation. Preferably, if it is determined that the blended fill layer does not satisfy the requirements of an engineering fill for the earthworks; the blended fill layer is modified or stabilized to meet the requirements. Preferably, the stabilization uses a binder to stabilize the blended fill layer. Further preferably, the binder is at least one of: cement or a lime binder. This invention has the following advantages and benefits: Reduction of transport movements for both materials imported and exported from site, this reduces emissions, Reduces the use of natural resources such as natural rock aggregates, Waste reduction, Cost savings. Brief description of the figures Further details, aspects and embodiments of the invention will be described, byway of example only, with reference to the drawings. In the drawings, like reference numbers are used to identify like or functionally similar elements. Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. Figure 1 is a flow chart of the steps of the method according to an embodiment of the invention; Figure 2 is cross sectional view of a pre-construction site before the method of the invention is performed; Figure 3 is a cross sectional view of the site of Figure 2 after the vegetation and upper topsoil have been removed: Figure 4 is a cross sectional view of the site of figure 3 showing the blending by rotavation. Detailed description of Invention Examples will now be described with reference to the accompanying drawings in which there is illustrated an example of a method for preparing and using an engineered soil fill for earthworks on a site. However, it will be appreciated by a skilled artisan that the concepts disclosed are not limited to the specific examples herein described and as illustrated in the accompanying drawings. Furthermore, because the illustrated embodiments of the present invention may, for the most part, be implemented using components known to those skilled in the art, details will not be explained in any greater detail than that considered necessary as illustrated below, for the understanding and appreciation of the underlying concepts of the present invention and in order not to obfuscate or distract from the teachings of the present invention. Fig. 1 is a flowchart of an example process 100. In some implementations, one or more process blocks of Fig. 1 may be performed by a device or an operative on the site. As shown in Fig. 1, the method of an embodiment of the invention 100 may include determining a geographical region on an earthworks site, and dividing the geographical region into an upper topsoil layer 204, a lower topsoil layer 206 and a subsoil layer 208. In some examples each subsequent layer will have a smaller % total organic matter content (TOMC) than the previous layer (block 102). For example, an operative or a device may determine a geographical region on the earthworks site, and divide the geographical region into an upper topsoil layer 204, a lower topsoil layer 206 and a subsoil layer 208, where each subsequent layer may have a smaller % total organic matter content (TOMC) than the previous layer, as described above. As also shown in Fig. 1, process 100 may include testing one or more of the layers, using chemical analysis to determine the total organic matter content (TOMC) of one or more of the upper, lower and subsoil levels (block 104). For example, an operative may test each layer, using chemical analysis either on site, or off-site at a laboratory to determine the total organic matter content (TOMC) of each of the upper, lower and subsoil levels, as described above. As further shown in Fig. 1, process 100 may include removing the upper topsoil layer 204to a predetermined first depth from the top of the upper topsoil layer (block 106).,in some examples of the invention this is done when the TOMC of the upper topsoil layer is greater than 2% For example, an operative may remove the upper topsoil layer 204 to a predetermined depth, when the TOMC of the upper topsoil layer 204 is greater than 2%, as described above. As also shown in Fig. 1, process 100 may include blending the lower topsoil layer 206 and the subsoil layer 208 to a specified second depth from the top of the lower topsoil layer 206 to produce a blended fill layer with a TOMC value between the TOMC value for the original lower topsoil layer 206 and the TOMC value for the subsoil layer 208 (block 108). Preferably the second specified depth is at least 400mm For example, an operative or a device may blend the lower topsoil layer 206 and the subsoil layer 208 to a specified depth to produce a blended fill layer with a TOMC value between the TOMC value for the original lower topsoil layer 206 and the TOMC value of the subsoil layer 208, as described above. As further shown in Fig. 1, process 100 may include determining the TOMC of the blended layer (block 110). For example, device may determine the TOMC of the blended fill layer, as described above. As also shown in Fig. 1, process 100 may include when the TOMC of the blended fill layer is no greater than 2% performing one of more geotechnical tests on the blended fill layer to determine if the blended fill layer satisfies one or more target requirements of an engineering fill for the earthworks (block 112). For example, an operative or device may, when the TOMC of the blended layer is no greater than 2%, perform one of more geotechnical tests on the blended fill layer to determine if the blended fill layer satisfies the one or more target requirements of an engineering fill for the earthworks, as described above. As further shown in Fig. 1, process 100 may include, if the one or more target requirements are satisfied using the blended fill layer either in situ as engineering fill, or excavating the blended fill layer for use as engineered fill in an alternative location on the site (block 114). For example, if the requirements are satisfied the blended fill layer may be used either in situ as engineering fill or excavating the blended fill layer for use as engineered fill in an alternative location on the earthworks site, as described above. As also shown in Fig. 1, process 100 may include compacting and / or stabilizing the engineered fill in situ or in the alternative location either on the earthworks site, or in a location off site, and testing the compacted and / or stabilized fill for compliance with the one or more target requirements for the site (block 116). For example, the engineered fill may be compacted and / or stabilized in situ at the earthworks site, or in the alternative location, and testing the compacted and / or stabilized fill for compliance with the specification for the site, as described above. Although Fig. 1 shows example blocks of process 100, in some implementations, process 100 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in Fig. 1. Additionally, or alternatively, two or more of the blocks of process 100 may be performed in parallel. Figure 2 is a cross sectional view 200 of the layers in a pre-construction stage on the earthworks site. As shown, the layers comprise a topmost vegetation layer 202. An upper topsoil layer 204, a lower topsoil layer 206, and a subsoil layer 208. Typically, the upper topsoil layer is 150mm deep, with an example Total Organic Matter Content T(OMC) of 5%. The lower subsoil layer 206 is also approximately 150mm deep, but with a reduced TOMC content of 3%, less than the upper topsoil layer 204. The subsoil layer 208 has a depth of approximately 250mm, with an TOMC content of 1%. Once the upper topsoil layer 204 is deemed suitable for use it can be incorporated into the earthworks. The area of upper topsoil 204 will be cleared of vegetation 202, whether this is trees, shrubs, grass, roots or any waste matter from vegetation, or a mixture. The vegetation 202 would be processed separately. Whether it is re-used or deposited. The upper topsoil layer 204 will be stripped to a predetermined depth that removes higher organic topsoil and rootlets. This material that has been removed from the upper topsoil layer 204 will be stockpiled on site for either reuse on site or removal from site. Figure 3 shows the cross-sectional view of the pre-construction site 200 of FIG. 2 after the vegetation 202 and upper topsoil layer 204 have been stripped from the pre-construction site 200. The resultant site is then left with the lower topsoil layer 206 and the subsoil layer 208. The TOMC of these two layers is unchanged. To ensure the lower topsoil layer 206 is suitable for re-use, initially laboratory chemical analysis is required to determine the organic matter content of the lower topsoil layer 206 and the material it would be blended with to determine the blending ratios. In a preferred embodiment of the invention, the lower topsoil layer will be blended with the subsoil layer 208, and so the TOMC for this subsoil layer 208 is also determined. Determining the total organic matter content of soil layers is essential for assessing soil fertility, quality, and its suitability for various agricultural or environmental purposes. There are several methods that can be used to determine soil total organic matter content, ranging from simple and quick techniques to more elaborate laboratory analyses. Here are some common methods: Loss-on-lgnition (LOI) Method: This is a known method for estimating soil total organic matter content. Weigh a sample of the soil and heat it in an oven at around 350-550°C for several hours to burn off the organic matter. What remains is the mineral content. The difference in weight before and after heating is the total organic matter content. This method is relatively simple and inexpensive but may overestimate organic matter if there are carbonates in the soil. Walkley-Black Method: This method involves wet oxidation with potassium dichromate. Organic matter reacts with the dichromate, and the remaining dichromate is titrated to determine the organic carbon content. It provides a more accurate estimate of organic carbon content compared to LOI. Solvent Extraction Method: This method involves the use of a solvent, such as potassium hydroxide (KOH), to dissolve organic matter. The solution is then titrated to determine the amount of organic carbon. It is more suitable for soils with a high total organic matter content. Near-lnfrared Spectroscopy (NIRS): NIRS is a non-destructive, rapid, and accurate technique for measuring total organic matter content. It relies on the absorption of near-infrared light by organic compounds in the soil. NIRS instruments can provide immediate results in the field or lab. Soil Organic Carbon Test Kits: Commercial test kits are available for rapid on-site assessment of soil organic carbon content. These kits usually involve colorimetric or titration methods and come with detailed instructions. Laboratory Analysis: In a laboratory, precise analyses can be performed using equipment like a Total Organic Carbon (TOC) analyzer. This method directly measures the carbon content and is highly accurate but requires specialized equipment. The choice of method should consider factors such as the expected organic matter content in the soil, available equipment, budget, and the level of precision required. For most routine soil testing, loss-on-ignition, Walkley-Black, or commercial test kits are commonly used due to their practicality and reasonable accuracy. The lower topsoil 206, with a determined TOMC, will then be blended with the subsoil layer 208 which also has a known TOMC value. Preferably, the blending is done by rotovating the lower topsoil 206using rotavator 300 with the underlaying subsoil 208. The rotavator blending is done to a predetermined depth as shown in figure 4. As shown, the lower topsoil layer 206has a TOMC of 3% and the subsoil layer 208 has an TOMC of 1%. The lower topsoil layer 206 and the subsoil layer 208 are mixed to a specified depth using rotavation to provide a blended uniform fill material 210 with an organic content lower than what is permitted by the earthwork's specification. Preferably, the specified depth for the blended fill material is at least 400mm. In this embodiment of the invention, the resulting TOMC of the blended material is 1.75%, which is below the 2% limit that is specified for the material as one or more of the target requirements. The blended material 210 canthen be compacted or stabilised on the earthworks site depending on the one of more target requirements of the site specification or excavated and engineered in areas of filling. The compacted or stabilised blended engineered fill 210 is then tested in accordance with the one or more target requirements of the Earthwork Specification to ensure it complies with the specification. Geotechnical testing of the blended material 210 will then be carried out to classify the material and to determine its engineering properties, and whether the blend can be engineered in accordance with the one or more target requirements of the Earthworks Specification. These tests include the following: Atterberg limits, This is a laboratory test to determine the fine-grained soil properties and their suitability for earthworks or construction projects. It helps assess the plasticity, liquidity, and shrink-swell characteristics of soils. The Atterberg Limit test primarily involves three key soil consistency limits: the liquid limit (LL), plastic limit (PL), and shrinkage limit (SL). Liquid Limit (LL): The liquid limit is the moisture content at which a soil transitions from a liquid-like state to a plasticlike state. To determine the liquid limit, a soil sample is gradually mixed with water on a standard testing apparatus (usually a Casagrande cup) until it acquires a specific consistency. This consistency is defined by the point at which a groove made in the soil mass closes for a distance of 1 / 2 inch when subjected to 25 blows. The moisture content at this point is recorded as the liquid limit. Plastic Limit (PL): The plastic limit is the moisture content at which a soil transitions from a plastic-like state to a semisolid state. To determine the plastic limit, a soil sample is gradually mixed with water until it forms small, thread-like shapes without breaking apart. The moisture content at which this occurs is recorded as the plastic limit. Shrinkage Limit (SL): The shrinkage limit is the moisture content at which further drying of the soil will not cause any further volume reduction. To find the shrinkage limit, a soil sample is prepared with a specific moisture content and then allowed to dry in an oven. The moisture content at which the soil no longer shrinks upon drying is recorded as the shrinkage limit. Once these three limits (LL, PL, SL) are determined, the soil can be classified into various categories based on its plasticity. Particle size distribution, Moisture content, Moisture Condition value and calibration, Particle Density and compaction curves, Laboratory Californian Bearing Ratio (CBR) and swell tests. The CBR test is a standardized laboratory test used to evaluate the strength and bearing capacity of subgrade soils, subbase materials, and base course materials commonly used in road construction and pavement design. The primary purpose of the CBR test is to assess how a soil sample's strength compares to a standard material called crushed limestone. The test involves the following steps: a. Preparation of a soil sample from the field. b. Compacting the soil sample at a specified moisture content and density inside a CBR mold. c. Penetrating the compacted soil with a standard piston at a constant rate of penetration. d. Measuring the load required to achieve specific penetration depths. e. Calculating the CBR value, which is the ratio of the load required to penetrate the soil sample to a certain depth to the load required to penetrate the standard crushed limestone material to the same depth. The CBR value is expressed as a percentage, with higher values indicating better soil strength and bearing capacity. Soils with higher CBR values are more suitable for supporting heavy loads in road construction. Swell Test: The swell test, also known as the free swell test or the expansion index test, is used to measure the potential volume change (swelling) that a soil undergoes when it absorbs water. This test is particularly important when dealing with expansive soils, such as clayey soils, which can significantly expand when wet and shrink when dry, causing problems in construction and infrastructure. The swell test involves the following steps: a. Collecting a soil sample from the field. b. Drying the sample to its initial dry weight in an oven. c. Immersing the dried sample in water for a specified period to allow it to fully absorb moisture. d. Measuring the volume increase of the soil sample after absorbing water. e. Calculating the swell potential as a percentage, which is the change in volume divided by the initial dry volume. Soils with a high swell potential are considered problematic for construction since their volume changes can lead to ground heaving, foundation instability, and damage to structures. Engineers use the results of swell tests to design foundations and earthworks that can accommodate the potential soil expansion. If it is determined that the blended fill layer 210 does not satisfy the one or more target requirements of an engineering fill for the earthworks; the blended fill layer 210 is modified or stabilized to meet the one or more target requirements. If the blended engineered fill 210 requires modification or stabilisation with a binder such as lime or cement, then further geotechnical and chemical testing is required to determine whether the material can be modified or stabilised without adverse swell or chemical reactions, and whether the material can achieve strength and stiffness values in accordance with the one or more target requirements of the Earthworks Specification. These tests included: Moisture content, Moisture Condition value and calibration, Particle Density and compaction curves, Soaked Laboratory Californian Bearing Ratio (CBR) and swell tests. Unconfined Compressive Strength (UCS) The Unconfined Compressive Strength (UCS) test is used in geotechnical engineering and material science to determine the strength characteristics of cohesive soils, such as clays and silts, under unconfined conditions. Unlike other compression tests that require confining pressures, the UCS test is performed on soil specimens without lateral restraint. The Unconfined Compressive Strength test is conducted using the following steps: Sample Collection: A soil sample is collected from the field using a sampling tube or another appropriate method. The sample should be carefully handled to avoid altering its moisture content or structure. Sample Preparation: The collected soil sample is prepared in the laboratory by removing any organic materials, stones, or debris and drying it to a specific moisture content if needed. The sample is then molded into a cylindrical shape with a specified diameter and height. Setting the Test Apparatus: A typical UCS test apparatus consists of a vertical loading device and two parallel plates or platens. The upper platen is attached to the loading device and can apply a vertical load to the soil specimen. The lower platen provides a flat surface for the soil specimen to rest on. Mounting the Specimen: The cylindrical soil specimen is carefully placed on the lower platen. The specimen should be centered and aligned properly to ensure uniform loading. Application of Vertical Load: A vertical axial load is applied at a constant rate to the top of the soil specimen. The rate of loading is typically specified in the testing standards. Monitoring Deformation: During the test, the deformation or axial strain of the soil specimen is monitored continuously. This is done using displacement transducers or extensometers that measure the vertical displacement of the specimen. Recording Failure: The test continues until the soil specimen fails or reaches its maximum compressive strength. Failure is typically defined as a significant reduction in load-carrying capacity or when the specimen starts to deform rapidly. Calculation: The Unconfined Compressive Strength (UCS) is calculated by dividing the maximum axial load at failure by the cross-sectional area of the specimen. The formula for UCS is typically expressed as: UCS = Maximum Load at Failure / Cross-Sectional Area of Specimen The UCS test provides critical information about the soil's shear strength, cohesion, and load-bearing capacity under unconfined conditions. In the foregoing specification, the invention has been described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications and changes may be made therein without departing from the scope of the invention as set forth in the appended claims and that the claims are not limited to the specific examples described above. Furthermore, those skilled in the art will recognize that boundaries between the above-described operations are merely illustrative. The multiple operations may be combined into a single operation, a single operation may be distributed in additional operations and operations may be executed at least partially overlapping in time. Moreover, alternative embodiments may include multiple instances of a particular operation, and the order of operations may be altered in various other embodiments. However, other modifications, variations and alternatives are also possible. The specifications and drawings are, accordingly, to be regarded in an illustrative rather than in a restrictive sense. 5 In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word 'comprising' does not exclude the presence of other elements or steps than those listed in a claim. Furthermore, the terms 'a' or 'an,' as used herein, are defined as one or more than one. Also, the use of introductory phrases such as 'at least one' and 'one or more' in the claims should 10 not be construed to imply that the introduction of another claim element by the indefinite articles 'a' or 'an' limits any particular claim containing such introduced claim element to inventions containing only one such element, even when the same claim includes the introductory phrases 'one or more' or 'at least one' and indefinite articles such as 'a' or 'an.' The same holds true for the use of definite articles. Unless stated otherwise, terms such as 'first' and 'second' are used to arbitrarily distinguish 15 between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage. 06 12 24

Claims

1. A method for preparing and using an engineered soil fill for earthworks on a site, that reuses topsoil from the site comprising the steps of:determining a geographical region on the site, and dividing the geographical region into an upper topsoil layer, a lower topsoil layer and a subsoil layer, and at least one subsequent layer where each subsequent layer will have a % total organic matter content, TOMC;testing one or more layers, using chemical analysis to determine total organic matter content, TOMC, of one or more of the upper, lower and subsoil levels;removing the upper topsoil layer to a predetermined first depth from the top of the upper topsoil layer,blending the lower topsoil layer and the subsoil layer to a specified second depth from the top of the lower topsoil layer to produce a blended fill layer with an TOMC determined as having a TOMC value between a first TOMC value for the original lower topsoil layer and a second TOMC value for the subsoil layer;determining the TOMC of the blended fill layer;when the TOMC of the blended fill layer is no greater than 2% performing one or more geotechnical tests on the blended fill layer to determine whether the blended fill layer satisfies one or more target requirements of an engineering fill for the earthworks;when the one or more target requirements of an engineering fill are satisfied, using the blended fill layer including material from the lower topsoil layer, either in situ as engineering fill, or excavating the blended fill layer for use as engineered fill in an alternative location on the site;compacting and / or stabilizing the engineered fill in situ or in the alternative location; andtesting the compacted and / or stabilized fill for compliance with the one or more target requirements for the site.

2. The method of claim 1 wherein the specified second depth is at least 400mm.

3. A method as claimed in any preceding claim wherein each subsequent layer will have a smaller % total organic matter content, TOMC, than the preceding layer.06 12 244. The method of any preceding claim wherein the lower topsoil layer and the subsoil layer are blended by rotavation.

5. The method of any preceding claim wherein the one or more geotechnical tests comprise one or more of the following: Atterberg limit; particle size distribution, moisture content, moisture condition value and calibration; particle density and compaction, Californian bearing ratio, swell test.

6. The method of any preceding claim wherein the testing of the compacted and / or stabilized engineering fill comprises performing one or more of the following tests: moisture content; moisture condition value and calibration; particle density and compaction; Californian bearing ratio, swell test, and unconfined compressive strength.

7. The method of any preceding claim wherein removing the upper topsoil layer to the predetermined first depth removes topsoil, and any roots or waste matter from vegetation.

8. The method of any preceding claim wherein, if it is determined that the blended fill layer does not satisfy the one or more target requirements of an engineering fill for the earthworks; the blended fill layer is modified or stabilized to meet the one or more target requirements.

9. The method as claimed in claim 8 wherein the blended fill layer is stabilised using a binder.

10. A method as claimed in claim 9 wherein the binder is at least one of: a cement binder, a lime binder.

Images