Pendular soil modification system (PSM)

Abstract

This disclosure describes a system and method for modifying soil properties, particularly for improving the stability and strength of soft and fine-grained soils. The system utilizes a low relative humidity (RH) air generator to produce a low RH airflow, which is introduced into the soil through a perforated duct. An airflow circulating mechanism drives the air through the duct, where it interacts with the soil moisture, reducing the moisture content and increasing the shear strength and reducing the compressibility of the soil. The method involves generating the low RH airflow and introducing it into the soil through the perforated duct. The system and method are particularly useful for treating fine-grained soils and for utilizing dredged sediments as construction materials, reducing environmental impact and costs.

Description

[0001] PENDULAR SOIL MODIFICATION SYSTEM (PSM)

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of U.S. Provisional Application Ser. No. 62 / 553,143. filed on 14 February 2024 and entitled “Pendular Soil Modification System (PSM).” The entire contents of which are incorporated herein by reference.

[0004] FIELD OF THE DISCLOSURE

[0005] The present disclosure relates to the field of geotechnical engineering, specifically to systems and methods for modifying soil properties, particularly for improving the stability and strength of soft and fine-grained soils.

[0006] BACKGROUND

[0007] Various types of soil deposits exist, including coarse-grained materials like cobbles, gravels, and sands, and fine-grained materials such as silts and clays, as well as mixtures of such soils. Rivers transport sediments to oceans and lakes, including large volumes of fine-grained sediments. These fine-grained soils, often found in coastal and inland areas, present challenges for construction projects due to their low shear strength and high compressibility, especially when they have a high water content. Ports and similar structures must often be implemented in areas where these fine sediments prevail, further exacerbating the challenges.

[0008] Current methods for addressing these challenges include techniques such as reinforcing the soil with cement or gravel inclusions, applying pre-loading and drainage, installing deep foundations, and mixing with stabilizing agents like lime or polymers. However, these methods often prove to be impractical, costly, or ineffective, particularly when applied to fine-grained soils like silts and clays. These soils require large volumes of stabilizing agents, sometimes without any significant improvement after mixing. In many cases, conventional approaches need to remove and replace soil, which is costly and timeconsuming. Furthermore, the dredged material, consisting of soft and plastic sediments, is challenging to utilized as a backfill material. The disposal of dredged fine sediments, often contaminated, also poses significant environmental challenges, with current solutions involving costly offshore disposal, which can also generate severe environmental effects and high hauling costs.

[0009] The limitations of current soil stabilization methods often result in waste disposal areas that cannot be utilized to support structures. This is a significant problem in various regions, including coastal areas and ports, where large quantities of fine sediments are continuously deposited and require dredging. The dredged material, typically a mixture of fine sediments and contaminants, is difficult to stabilize and often requires disposal in designated offshore areas, leading to further environmental concerns and high costs for hauling and disposal. The inability to effectively stabilize and utilize these materials represents a significant challenge in terms of financial and environmental costs. The current methods also fail in providing a sustainable and low-cost alternative for modifying soil properties, and in effectively treating fine-grained soils. The existing methods also do not utilize the potential energy that the soil has, nor the use of a psychrometric properties to determine the temperature needed for a desired air relative humidity to treat the soil.

[0010] Therefore, an objective of the present disclosure is to overcome the limitations of current soil stabilization methods, at least in part, by providing an improved system and method for modifying soil properties, that allows for the reutilization of dredged sediments, reduces the environmental impact of their disposal, provides a sustainable and low-cost alternative, effectively treats fine-grained soils, and utilizes the potential energy of the soil, while also providing a method that utilizes the psychrometric properties to determine the temperature needed for a desired air relative humidity.

[0011] BRIEF SUMMARY

[0012] The present disclosure refers to a system for modifying soil, comprising a low Relative Humidity (RH) air generator configured to generate a low RH airflow, a perforated duct configured to be installed within the soil, and an airflow circulating mechanism connected to the low RH air generator configured to introduce the low RH airflow into the perforated duct at one end. The system modifies the soil by controlling its moisture content.

[0013] Additionally, the present disclosure also describes a method for modifying soil, characterized by the steps of generating a low Relative Humidity (RH) airflow with a low RH air generator, and introducing said low RH airflow into a perforated duct at one end, configured to allow the airflow to interact with the soil moisture. The method modifies the soil by controlling its moisture content.

[0014] BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 illustrates an embodiment of a system for soil modification comprising a perforated duct with an airflow circulating mechanism connected to a low Relative Humidity generator.

[0016] Figure 2A illustrates an exploded view of the disposition of a perforated duct in connection with inner ducts and outlet pipes. Figure 2B shows a cross section view of the perforated duct with one inner pipe, Figure 2C shows a cross section view with two inner pipes, and Figure 2D shows a cross section view with an outlet pipe surrounding the perforated duct.

[0017] Figure 3 illustrates an embodiment of a system for soil modification as described in Figure 1, with a plurality of vertical pipes installed at predetermined intervals across a treatment area.

[0018] Figure 4 illustrates a plan view of the area of influence exerted by each perforated duct installed in the ground. The radial extent of this influence zone varies depending on soil type, grain size distribution, and moisture content.

[0019] Figure 5 illustrates the general concept of a system for soil modification in a horizontal application. It is shown a low relative humidity generator and an airflow circulating mechanism that increases air pressure generating low RH airflow within the duct system.

[0020] Figure 6 illustrates a plan view of a possible layout for perforated duct strips in a horizontal application of a system for soil modification.

[0021] Figure 7 illustrates a plan view of the area of influence surrounding a perforated duct used for soil drying in a horizontal application of a system for soil modification, where the radius of influence varies depending on soil characteristics.

[0022] Figure 8 illustrates an application of a system for soil modification for treating angled excavations. The figure shows the adaptability of the system for soil modification to irregular terrain, with perforated duct strips installed progressively from the bottom up at intermediate depths.

[0023] Figure 9 provides a lateral view of a system for soil modification using a horizonal configuration of a perforated duct.

[0024] Figure 10 illustrates a horizontal application of a system for soil modification within a trench, showing the post-installation of the perforated ducts.

[0025] Figure 11 presents the results of a system for soil modification testing on a soil sample, demonstrating the reduction of moisture content and volume, and the increase in shear strength over time.

[0026] DETAILED DESCRIPTION

[0027] The present disclosure relates to a system and a method for modifying soil properties, specifically, to improve the stability and strength of soft and fine-grained soils. These types of soils, which include silts and clays, are often characterized by low shear strength and high compressibility, particularly when they have a high-water content, making them challenging for construction and infrastructure projects. Existing methods for stabilizing these soils, such as reinforcement with cement or gravel, pre-loading and drainage, deep foundations, or mixing with stabilizing agents like lime or polymers, often prove to be impractical, costly, or ineffective, especially with fine-grained materials.

[0028] Furthermore, the disposal of dredged fine sediments, often contaminated, poses significant environmental challenges. In view of the foregoing, the present disclosure provides a more efficient, sustainable, and cost-effective approach to soil modification, that also allows for the reuse of dredged material and reduces the environmental impact of their disposal.

[0029] In reference to Figure 1, the present disclosure is directed to a system (10) comprising a low Relative Humidity (RH) air generator (25) configured to generate a low Relative Humidity (RH) airflow (70), a perforated duct (30) configured to be installed within the soil (60), and an airflow circulating mechanism (40) connected to the low RH generator (25) configured to circulate the low RH airflow (70) into the perforated duct (30) at one end.

[0030] The system (10) modifies the soil (60) through the control of its moisture content, by taking into account the relationship between air conductivity and water content in soil (60). The principle of operation of the present invention consists of reducing water content in the soil (60), increasing the air conductivity, while the water conductivity decreases. This principle allows the system (10) to use the air phase as the primary medium for extracting moisture from the soil (60). As the soil (60) dries, the air conductivity increases, allowing for a more efficient transfer of moisture from the soil (60) to the low RH airflow (70). This relationship is not linear; rather, as the soil (60) gets drier, the air conductivity increases at a higher rate, while the water conductivity decreases exponentially, making it harder to extract water using methods that rely on water flow.

[0031] In one embodiment, the system (10) relies on vapor transfer, which is facilitated by the increase in air conductivity. As the soil dries, the permeability of the soil to air increases, which makes the system (10) more efficient as the soil dries. At higher moisture contents, the water conductivity is higher, while the air conductivity is lower. As the soil dries, the air conductivity increases, and the water conductivity decreases. The system (10) takes advantage of this principle by using air as the medium for moisture extraction, and by drying the soil, the system (10) facilitates the movement of air through the soil (60). This is in contrast to systems that rely on water conductivity, which become less efficient as the soil dries.

[0032] To generate the low RH airflow (70), the system (10) uses a low RH air generator (25), which is configured to reduce the relative humidity of the ambient air. In general, it should be understood that increasing the temperature of the air reduces its relative humidity. The desired RH for system (10) soil treatment is a function of the ambient air RH and temperature. The system (10) can determine the precise temperature to which the ambient air must be heated to achieve a specific relative humidity, which is necessary to effectively dry the soil (60), by increasing the temperature of the air, the relative humidity decreases, allowing the air to absorb more moisture from the soil.

[0033] The system (10) does not need to use very high temperatures in order to reduce the relative humidity, and a temperature of around 50°C is often enough to achieve the desired relative humidity. Ranges between 20°C and 400°C can also be used, depending on the required treatment speed and terrain. Using a psychrometric chart, the system (10) can determine the temperature that needs to be applied to the air to achieve a certain level of dryness. The low RH airflow (70), generated by the low RH generator (25) is then introduced into the soil (60) through a perforated duct (30), with the airflow circulating mechanism (40) being responsible for moving the low RH airflow (70) from the low RH air generator (25) to the perforated duct (30), where it is introduced at one end. The low RH airflow (70) then interacts with the soil moisture (80), reducing the soil moisture content, increasing the shear strength, and reducing the compressibility of the soil (60).

[0034] The low RH air generator (25) transforms ambient air into a low RH airflow (70) which is capable of absorbing moisture from the soil (60). The low RH air generator (25) is connected to the airflow circulating mechanism (40), which introduces the generated low RH airflow (70) into the perforated duct (30), from where it reaches the soil (60). The low RH air generator (25) is configured to generate the low RH airflow (70) within a temperature range of 20°C to 400°C. In preferred embodiments, the low RH airflow (70) is generated to have a temperature between 50°C and 100°C, which provides an optimal balance between energy consumption and drying efficiency.

[0035] In one embodiment, the low RH air generator (25) comprises a heating element (21), which is selected from a group that includes electric resistance heaters, solar heating systems, gas heaters, heat exchangers, induction heaters, and combinations thereof. This heating element (21) elevates the temperature of the air, reducing its relative humidity. It should be noted that the specific type of heating element (21) is chosen based on factors such as the availability of resources, cost effectiveness, and the specific requirements of the treatment site.

[0036] In another embodiment, the low RH air generator (25) may comprise a mixing mechanism (22) that blends air with varying relative humidity levels to achieve the desired low RH airflow (70). This mixing mechanism (22) allows for a fine-tuning of the air’s RH, especially in environments where the ambient air has a high moisture content. This mixing mechanism (22) can be used together with the heating element (21) for greater control over the relative humidity of the airflow (70).

[0037] In another embodiment, the low RH air generator (25) is a standalone unit, positioned at the surface near the treatment area, where it is connected to the airflow circulating mechanism (40) through a hose line. In another embodiment, the low RH air generator (25) and the airflow circulating mechanism (40) can be integrated into a single unit. The low RH air generator (25) can be modular, allowing for ease of transportation and installation at different treatment sites.

[0038] The low RH air generator (25) can be powered by various energy sources, including electricity, gas, or solar power or the combination thereof. In embodiments utilizing solar energy, the low RH air generator (25) is connected to solar panels, which convert solar energy into electricity to power any of the various energy sources, or even that solar energy can be used to heat the low RH airflow (70).

[0039] The system (10) for modifying soil (60) also includes a perforated duct (30), which is configured to be installed within the soil (60). The perforated duct (30) serves as the primary conduit through which the low RH airflow (70) is introduced into the soil (60) to facilitate the drying process. This is carried out by distributing the low RH airflow (70) within the soil (60), allowing it to interact with the soil moisture (80) and promote the extraction of water vapor.

[0040] The perforated duct (30) is connected at one end to the airflow circulating mechanism (40), which introduces the low RH airflow (70) into the duct. The other end of the perforated duct (30) may be open or closed, depending on the specific embodiment of the system (10). The perforated duct (30) comprises perforations along its length, which are positioned to allow for a uniform distribution of the low RH airflow (70) within the soil (60) and to maximize the contact between the low RH airflow (70) and the soil moisture (80).

[0041] The perforated duct (30) can be fabricated from a plurality of materials. These materials are selected from a group consisting of: rigid polyvinyl chloride (PVC), flexible polyvinyl chloride (PVC), steel, aluminum, composite materials, and combinations thereof. The choice of material depends on factors such as the desired flexibility, durability, cost, and the specific conditions of the soil (60). For instance, flexible PVC perforated ducts are suitable for installations where some flexibility is required, such as in trenches or sloped excavations. Alternatively, a rigid material such as steel or aluminum can be used where more durability is needed. The perforated duct (30) may be of different diameters and lengths, depending on the specific application and the volume of soil (60) to be treated.

[0042] In one embodiment, the perforated ducts (30) can be wrapped in a porous engineering material (32), said wrapping serves a dual purpose: it prevents soil particles from entering and potentially clogging the perforations in the perforated ducts (30), while simultaneously allowing for the unimpeded transfer of water vapor between the low RH airflow (70) within the perforated ducts (30) and the surrounding soil (60). This feature enhances the efficiency of the drying process by ensuring that the low RH airflow (70) can interact with the soil moisture (80) without being impeded by soil particles. The porous engineering material (32) can be selected from non-woven geotextile fabricated from geosynthetic materials, or natural fiber textiles. In one particularly embodiment, the porous engineering material (32) is a non-woven geotextile. The technical effect of having a non-woven geotextile is first, allowing the efficient airflow between the surrounding soil and the perforated duct, and second, preventing soil particles from getting into the perforated pipe with the consequent prevention of borehole cavities and also prevent perforated duct clogging.

[0043] The system (10) for modifying soil (60) also incorporates an airflow circulating mechanism (40), which is connected to the low RH air generator (25) and configured to circulate the low RH airflow (70) into the perforated duct (30) at one end. The airflow circulating mechanism (40) is also connected at one end to the perforated duct (30), introducing the low RH airflow (70) into the perforated duct (30). In other words, the airflow circulating mechanism (40) conducts the low RH airflow (70) into the perforated duct (30). In one embodiment, the airflow circulating mechanism (40) can be a pipe, a hose, and a multiple chamber duct.

[0044] In another embodiment, the airflow circulating mechanism (40) besides only conducts, can increase the pressure of the low RH airflow (70) to ensure that the low RH airflow (70) is evenly distributed through the perforated duct (30) and into the surrounding soil (60), thus enabling the effective extraction of moisture. For increasing the pressure of the low RH airflow (70) the airflow circulating mechanism (40) can be connected to an element that increase the pression of the air such as, air compressor, fans, blowers, turbines, or positive displacement pumps, and the combination thereof. Also, the airflow may be produced naturally by connecting the two duct ends with a different natural ambient air pressure locations such as one end at the top and the other one at the bottom of a hill. Particularly in this embodiment, the airflow circulating mechanism (40) can generate and maintain a controlled flow of the low RH airflow (70) through the system (10).

[0045] In one embodiment, the airflow circulating mechanism (40), is connected to an air compressor (41) capable of generating a high pressure low RH airflow (70), which is particularly useful for treating dense or compacted soils. In another embodiment, the airflow circulating mechanism (40) is connected to a fan (42) which is directed to applications where a lower pressure airflow is sufficient, such as in less dense soils or in shallow applications. The selection between an air compressor (41) and a fan (42) depends on factors such as the soil type, the depth of the perforated duct (30), and the desired flow rate of the low RH airflow (70). The airflow circulating mechanism (40) can also be designed to include control mechanisms to regulate the airflow rate and pressure.

[0046] In one embodiment, the airflow circulating mechanism (40) is a standalone unit connected to the low RH air generator (25) and the perforated duct (30), for example the airflow circulating mechanism (40) can be a hose line. In another embodiment, the airflow circulating mechanism (40) can be integrated with the low RH air generator (25) into a single unit. The airflow circulating mechanism (40) can also be modular, allowing for ease of transportation and installation at different treatment sites.

[0047] In some embodiments, the airflow circulating mechanism (40) can also be powered by different sources, including electricity or a combustion engine, in order to provide flexibility in implementation and to accommodate varying site conditions and resource availability, while also increasing efficiency, promoting energy savings, and allowing for the utilization of other forms of energy. The airflow circulating mechanism (40) can be used in conjunction with a temperature and Relative Humidity (HR) measuring system (35) to monitor the temperature of the low RH airflow (70).

[0048] Referring to Figure 1, one embodiment of the system (10) for soil modification is illustrated, which shows a vertical application. In this embodiment, the perforated duct (30) is installed vertically into the soil (60), using drilling techniques, reaching depths ranging from 5 m to 100 m, or even deeper. The low RH airflow (70) is introduced at the bottom of the duct and rises through the annular space of the perforated duct (30).

[0049] In the embodiment shown in Figure 1, the perforated duct (30), which can be a PVC pipe, connected to the airflow circulating mechanism (40) which may be a PVC pipe, as shown in the cross-section view of Figure 2A and Figure 2B. The low RH airflow (70) flows downward through the airflow circulating mechanism (40) to the bottom of the drilling depth and returns to the ground surface through the perforated duct (30), in this embodiment the airflow circulating mechanism (40) and the perforated duct (30) are symmetric, treating the soil (60) to increase its strength and reduce its compressibility with the vertical bottom-up airflow.

[0050] In another configuration of Figure 1, the perforated duct (30) with two internal pipes: one pipe (100) to hold a deep well submersible pump (51) to extract the groundwater and the second corresponding to the airflow circulating mechanism (40) to supply the downward low RH airflow (70), which will return to the ground surface flowing through the space between the perforated duct (30) and the internal pipes (100) and airflow circulating mechanism (40). This second configuration is shown in the cross-section view of the perforated duct (30) in Figure 2C and enables simultaneous groundwater removal and soil treatment.

[0051] In a third configuration, as the one shown in the cross-section view of the perforated duct (30) in Figure 2D, the perforated duct (30) may be as those described in Figure 2B and Figure 2C, but including an outlet pipe (34) surrounding the perforated duct (30) and airflow circulating mechanism (40). The outlet pipe (34) surrounds the perforated duct (30) and the airflow circulating mechanism (40), creating a protected space for the humidified air to flow back towards the surface. This prevents the humidified air from mixing with the surrounding soil (60) before it reaches the surface and ensures that the air is directed out of the treatment area.

[0052] The perforated duct (30) can be installed in different positions within the soil (60). That is, the perforated duct (30) can be installed vertically, horizontally, diagonally or in any position depending on the project requirements and soil characteristics.

[0053] In one embodiment, vertically installed perforated ducts (30) are suitable for treating deep soil deposits. It is well know that drilling techniques are used for reaching depths ranging from 5 m to 100 m, or even deeper.

[0054] In another embodiment, the perforated duct (30) can be installed horizontally within the soil (60). Horizontally perforated duct (30) can easily modify the properties of the soil (60) and is particularly well-suited for treating shallow soil deposits, for stabilizing sediment layers in sedimentation ponds, and for addressing soft soil conditions in sloped excavations or trenches. The horizontal arrangement of perforated ducts (30) includes embedding a network of these perforated ducts (30) within the soil (60) at a desired depth, allowing for a more uniform treatment of the soil (60), by using trenching or directional drilling techniques.

[0055] In additional embodiments, the perforated duct (30) can be installed at an angle within the soil (60) to address specific soil layers or to follow the contours of a slope. This angled installation allows the system (10) to target specific zones within the soil (60) that require treatment, providing a more tailored and efficient approach to soil modification. The angle of the perforated duct (30) can range from 1 degree to 89 degrees relative to the horizontal, or even a vertical installation when needed, depending on the specific requirements of the site and the project. For instance, a smaller angle may be used to treat shallow layers of soil (60) or to follow a gentle slope, while a larger angle may be used to target deeper soil layers or to address more pronounced slopes. The angle of the perforated duct (30) can be adjusted to ensure that the low RH airflow (70) is directed to the areas of the soil (60) that require the most treatment.

[0056] Other embodiments comprise a plurality of perforated ducts (30) arranged in a configuration to form a drying area within the soil (60). This arrangement allows for a more comprehensive and uniform treatment of the soil (60), particularly in situations where the treatment area is large. The plurality of perforated ducts (30) can be arranged in different patterns, such as a grid, a line, or a radial configuration, depending on the specific requirements of the project. For example, a grid pattern may be used to ensure a uniform treatment of a large area, while a radial configuration may be used to target a specific point or area.

[0057] The separation between the perforated ducts (30) can range from 1 m to 10 m, depending on the soil type, moisture content, and the desired treatment area. Preferred embodiments can range from 1.5 m to 5 m, or 1.5 m to 3 m. Finer soils may require a closer spacing of the ducts to ensure uniform drying.

[0058] Referring to Figure 4, there is shown a plan view of the area of influence exerted by each perforated duct installed in the ground. This area of influence is a radial zone surrounding each perforated duct (30) within which the low RH airflow (70) can effectively penetrate and modify the surrounding soil (60). The radial extent of this influence zone is variable, depending on factors such as soil type, grain size distribution, and moisture content. These factors affect the permeability of the soil (60) and thus the distance the injected low RH airflow (70) can effectively penetrate and modify the surrounding soil (60).

[0059] The area of influence shown in Figure 4 is larger in finer soils and smaller in coarse soils, as the water is harder to extract from the finer soils. Figure 4 shows a plurality of vertical perforated ducts (30) installed at predetermined intervals across a treatment area. It should be noted that additional patterns of perforated ducts (30) can be arranged in any configuration. This arrangement can be changed pursuing soil drying with low RH airflow (70) injection and / or groundwater extraction across a wider expanse of the soft ground (60).

[0060] The perforated duct (30) when installed horizontally can be seen in Figures 5 to 10. This horizontal configuration enhances the distribution of the low RH airflow (70) throughout the treatment area by increasing air conductivity as the soil (60) dries. The low RH airflow (70) flows through the perforated ducts (30), progressively extracting moisture from the soil (60).

[0061] The area of influence exerted by each perforated duct (30), as shown in Figures 6 and 7, is a radial zone, and the extent of this influence zone varies depending on factors such as soil type, grain size distribution, and moisture content. The system (10) can be installed in such a way that the areas of influence of each perforated duct (30) overlap, ensuring that the entire treatment area is effectively dried.

[0062] The perforated ducts (30) can be installed at different depths, allowing for the targeted treatment of specific soil layers. The horizontal arrangement of the perforated ducts (30) also allows for the system (10) to be used in conjunction with other soil modification techniques, such as groundwater extraction. In one embodiment, the groundwater extraction can be a submersible pump (51), said submersible pump (51) can be used to lower the water table, ensuring that the drying process is not hampered by the presence of free water.

[0063] In other embodiments, the low RH airflow (70) is introduced into the perforated ducts (30) at one end, and the humidified air is allowed to exit the ducts at the other end, or it is directed to a drying chamber for reuse in the system (10) (not shown). The drying chamber receives the airflow (70) after it has circulated through the perforated duct (30), wherein the drying chamber (90) is configured to dry the airflow (70) and reintroduce it into the system (10). The system (10) can also include a pumping system (50) located in proximity to the system for modifying soil (60) for extracting free water from the soil (60).

[0064] Referring to Figure 8, it illustrates an application of the system (10) for soil modification, specifically designed for treating angled excavations filled with soft sediments. In Figure 8, the perforated duct (30) is installed progressively from the bottom up at intermediate depths as the excavation is filled with soft sediments. This configuration allows for the treatment of the fill material as it is placed, guaranteeing flexibility in the installation of the perforated ducts (30).

[0065] In Figure 8, the perforated ducts (30) do not need to be perfectly straight, and that the low RH airflow (70) within the system (10) is not significantly affected by the alignment or shape of the ducts (30). This configuration is particularly advantageous when dealing with sloped or uneven excavations, where a rigid duct system would be difficult to install. The ability to install the perforated ducts (30) in a non-linear manner allows for the system (10) to conform to the specific geometry of the excavation, ensuring that the low RH airflow (70) is effectively distributed throughout the treatment area.

[0066] The low RH airflow (70) is introduced into the perforated ducts (30) interacting with the soil (60) to reduce its moisture content. The perforated ducts (30) are installed at intermediate depths for treating the soil (60) at different levels.

[0067] Referring to Figure 10, one embodiment of a horizontal application of the system (10) for soil modification within a trench is shown, with particular emphasis on the postinstallation of the perforated ducts (30). This Figure 10 depicts a practical method for deploying the system (10) in situations where a trench has already been excavated, or where a shallow treatment of the soil (60) is desired. The process begins with an excavator, equipped with a specialized trenching tool, creating a narrow and deep trench in the ground (60). This trenching tool minimizes the width of the excavation while maximizing its depth.

[0068] Following the trench excavation, perforated ducts (30), which in this embodiment are PVC pipes, are wrapped in the porous engineering material (32), which in this embodiment is a non-woven geotextile, are installed within the trench. The choice of flexible PVC for perforated ducts (30) allows for some adaptability in their placement, enabling the system (10) to accommodate minor variations in the trench profile and the soil conditions. The figure also shows that the perforated ducts (30) can be installed at different depths within the trench.

[0069] This post-installation method, as shown in Figure 10, provides a practical and versatile solution for soil improvement in various construction scenarios. The perforated ducts (30) are installed after the trench has been excavated, which means that the system (10) can be used to treat soil (60) in existing trenches without requiring extensive excavation. The perforated ducts (30) can be installed in a way that allows for the low RH airflow (70) to interact with the soil (60) at various depths.

[0070] In various embodiments, the system (10) also includes a temperature and Relative Humidity (HR) measuring system (35) configured to measure the temperature and the relative humidity (RH) of the low RH airflow (70) at different points within and outside the perforated duct (30), as shown in Figures 1 and 3. This temperature and RH measuring system (35) monitors and controls the soil (60) drying process, and can be composed of the group of sensors (110) or any device capable of providing information about temperature and RH.

[0071] In one embodiment, the sensors (110) are placed at the inlet of the perforated duct (30), at different depths within the duct (30), and at the outlet, allowing for detailed monitoring of the temperature and RH profile. The temperature and RH measuring system (35) can be located at any depth of the surface, for instance, may be placed at 2 m, 4 m, 6 m, 10 m, or even deeper within the soil (60), allowing for the monitoring of the temperature and RH of the low RH airflow (70) at different points during its travel through the soil (60). The temperature and RH measuring system (35) is connected to a control system, which is used to adjust the temperature and RH of the low RH airflow (70) as needed.

[0072] Method

[0073] The present disclosure also describes a method for modifying soil (60), characterized by the steps of generating a low Relative Humidity (RH) airflow (70) with a low RH air generator (25), and introducing said low RH airflow (70) into a perforated duct (30) at one end, configured to allow the airflow (70) to interact with the soil (60) moisture. This method modifies the soil (60) by controlling its moisture content. The method operates on the principle of vapor pressure transfer, whereby the low RH airflow (70) absorbs moisture from the soil, thereby drying it.

[0074] The present disclosure also discloses a method for modifying soil (60) properties, specifically designed to improve the stability and strength of soft and fine-grained soils. This method, is characterized by the steps of: generating a low Relative Humidity (RH) airflow (70) with a low RH air generator (25); and introducing said low RH airflow (70) into a perforated duct (30) at one end, configured to allow the airflow (70) to interact with the soil (60) moisture. This method modifies the soil (60) by controlling its moisture content, and it operates on the principle of vapor pressure transfer, whereby the low RH airflow (70) absorbs moisture from the soil (60), thereby drying it, as explained before.

[0075] In one embodiment of the method, the step of generating the low RH airflow (70) includes increasing the temperature of the airflow (70) with a heating element (21). This heating element (21) can be selected from a group consisting of electric resistance heaters, solar heating systems, gas heaters, heat exchangers, induction heaters, and the combination thereof. The heating element (21) increases the temperature of the air, thereby reducing its relative humidity.

[0076] In other embodiments, the step of generating the low RH airflow (70) includes generating the airflow using an air compressor (41) or a fan (42). The airflow circulating mechanism (40) is responsible for moving the low RH airflow (70) from the low RH air generator (25) to the perforated duct (30). The choice between an air compressor (41) and a fan (42) depends on factors such as the soil type, the depth of the perforated duct (30), and the desired flow rate of the low RH airflow (70).

[0077] The method may further comprise a step of pumping water located in the proximity of the perforated duct (30) with a submersible pump (51). This step is particularly useful in situations where the water table is high, as it helps to reduce the amount of free water in the soil (60), allowing for a more effective drying process.

[0078] The step of introducing said low RH airflow (70) into the perforated duct (30) is maintained continuously, achieving a relative humidity of the airflow (70) to lower than the threshold design value. The optimal time for the system (10) to operate depends on the type of soil and the desired level of modification. The system (10) monitors the soil’s moisture content and the air’s relative humidity to ensure that the soil is not over-dried.

[0079] In another embodiment, the method further comprises a step of directing the airflow (70) after it has interacted with the soil moisture (80), to a drying chamber (90), drying the airflow (70) within the drying chamber (90) and reintroducing the low RH airflow (70) into the perforated duct (30). This step improves the efficiency of the system (10) by reusing the low RH airflow (70) and reducing the amount of energy needed for the drying process.

[0080] The horizontal application of the system (10), illustrated in Figure 4, shows the low RH air generator (25) reducing the relative humidity of ambient air, and an airflow circulating mechanism (40) increasing air pressure and generating low RH airflow (70) within the duct system. The process comprises: Air preparation, where ambient air is dehumidified by the low RH air generator (25) and pressurized by the airflow circulating mechanism (40). This results in high-temperature, low-RH air. Afterwards, air is injected into a perforated duct system (30) embedded within the soft soil (60). Subsequently, as the dry air flows through the perforated ducts (30), a thermodynamic effect occurs by mixing it with the humid air within the soil (60). This mixing increases the RH of the injected air, with the degree of increase being proportional to the soil’s moisture content. It should be noted that the horizontal embodiment of the system (10) uses controlled airflow (70) through embedded ducts (30) to modify the soil’s moisture content and, consequently, its properties.

[0081] EXAMPLES

[0082] Example 1

[0083] In one example, the system (10) was implemented for stabilizing a soft soil deposit (60) in a coastal area. The soil (60), consisting primarily of silts and clays, had a high initial moisture content of approximately 90%, exhibited a low shear strength near 0 kPa, and had a high compressibility. The soil (60) was saturated, with a water table located approximately 4 meters below the surface. To modify this soil (60), a low RH air generator (25) was used to generate a low RH airflow (70). In this example, the low RH air generator (25) comprised a heating element (21) that heated ambient air to 100°C, reducing its relative humidity to a design value. The low RH air generator (25) was located at the surface, near the treatment area. A perforated duct (30), which was a PVC pipe (31) was wrapped in a porous engineering material (32), which was a non-woven geotextile. The perforated duct (30) was installed vertically into the soil (60) to a depth of 12 meters using drilling techniques. The pipe (31) had a diameter of 3 inches, and the perforations were distributed to allow adequate interaction between the airflow (70) and the soil (60).

[0084] The perforated duct (30) was installed to leave an annular space (33) for the return of humidified air. An air compressor (41) was used as the airflow circulating mechanism (40), connected to the low RH air generator (25) at one end, and to the perforated duct (30) at the other end. A submersible pump (51) was installed at the bottom of the perforated duct (30) to lower the water table. The pumping system (50) extracted free water from the soil (60), ensuring the system (10) could effectively dry the soil. A temperature and RH measuring system (35) monitored the temperature and the RH of the low RH airflow (70) at different points, including at the surface and at depths of 6 and 10 meters within the soil (60). An outlet pipe (34) surrounded the perforated duct (30) and the airflow circulating mechanism (40). The system (10) further comprised a drying chamber (90) configured to receive the airflow (70) after it had circulated through the perforated duct (30), and to dry the airflow (70) and reintroduce it into the system (10). A plurality of perforated ducts (30) were installed in a grid pattern, with a separation of 3 meters between each duct, to form a drying area within the soil (60).

[0085] The process began by drawing ambient air into the low RH air generator (25), where it was heated to 100°C by the heating element (21), reducing its relative humidity. The heated, low RH airflow (70) was then introduced into the perforated duct (30) at one end by the airflow circulating mechanism (40), in this case, an air compressor (41). The low RH airflow (70) traveled down the inner pipe and rose through the annular space (33) to interact with the surrounding soil (60).

[0086] The low RH airflow (70) extracted water vapor from the soil (60) through vapor pressure transfer. The water vapor was transported out of the soil through the perforated duct (30), and then to the drying chamber (90), where the water was separated from the air, and the air was reintroduced into the system (10). The submersible pump (51) lowered the water table, ensuring that the soil drying process was not hampered. The temperature and RH measuring system (35) continuously monitored the temperature and the RH of the low RH airflow (70), allowing for adjustments to the process.

[0087] This process resulted in a significant reduction in moisture content, with the soil (60) reaching approximately 50% moisture content after two weeks, an increase in shear strength to 300 kPa, and a significant reduction in its compressibility. The system (10) operated continuously, and the temperature of the airflow (70) was monitored and adjusted to maintain the desired relative humidity. The water table was lowered and maintained below the treatment depth by the submersible pump (51).

[0088] Example 2

[0089] With system (10) of Example 1, a laboratory test was conducted to demonstrate the effectiveness of the system (10). The test uses three chambers: a PSM treatment chamber, a treated soil (60) chamber, and an exhaust chamber. The PSM treatment chamber is used to generate the low RH airflow (70). In this chamber, ambient air is drawn and heated, reducing its relative humidity to the design value, using a heating element (21). The treated soil chamber contains the soil sample (60) to be treated.

[0090] The low RH airflow (70) from the PSM treatment chamber is introduced into this chamber through a perforated duct (30) using an air pump or a fan (42). The perforated duct (30) is embedded within the soil sample (60), allowing the low RH airflow (70) to interact with the soil moisture (80). The exhaust chamber receives the humid air after it has passed through the soil chamber. The air is extracted from the soil (60) in the form of water vapor. The test measures the relative humidity (RH) in each chamber, as well as the shear strength of the soil sample (60).

[0091] In figure 11 is shown the results of the laboratory test, said results show that as the system (10) operates, the relative humidity in the treated soil chamber decreases, while the shear strength of the soil increases, and the volume of the soil decreases.

[0092] The test also shows that the soil moisture (80) is transported out of the soil (60) by the perforated duct (30), through the air phase. In other words, the soil moisture (80) is converted to water vapor, which is transported out of the soil (60) by the perforated duct (30).

[0093] It must be understood that this invention is not limited to the embodiments described and illustrated above. A person skilled in the art will understand that numerous variations and / or modifications can be carried out that do not depart from the spirit of the invention, which is only defined by the following claims.

Claims

CLAIMS1. A system (10) for modifying soil (60), comprising: a low Relative Humidity (RH) air generator (25) configured to generate low Relative Humidity (RH) airflow (70); a perforated duct (30) configured to be installed within the soil (60); and an airflow circulating mechanism (40) connected to the low RH generator (25) configured to circulate the low RH airflow (70) into the perforated duct (30) at one end.

2. The system of Claim 1, wherein the low RH air generator (25) comprises a heating element (21) selected from the group consisting of: electric resistance heaters, solar heating systems, gas heaters, heat exchangers, induction heaters, and the combination thereof.

3. The system of Claim 1, wherein the airflow circulating mechanism (40) is connected to an air compressor (41).

4. The system of Claim 1, wherein the airflow circulating mechanism (40) is connected to a fan (42).

5. The system of Claim 1, wherein the perforated duct (30) is fabricated of a material selected from the group consisting of: rigid polyvinyl chloride (PVC), flexible polyvinyl chloride (PVC), steel, aluminum, composite materials, and the combination thereof.

6. The system of Claim 5, wherein the perforated duct (30) is wrapped in any type of porous engineering material (32), specifically, said porous engineering material (32) is geotextile.

7. The system of Claim 1, wherein the perforated duct (30) is installed in any configuration within the soil (60), specifically installed horizontally within the soil (60), installed vertically within the soil (60), installed in an inclined manner within the soil (60), and the combination thereof.

8. The system of Claim 1, further comprises a pumping system (50) located in proximity to the system for modifying soil (60) for extracting free water from the soil (60).

9. The system of Claim 1, further comprising a temperature and RH measuring system (35) configured to measure the temperature of the low RH airflow (70) at different points within and outside the perforated duct (30).

10. The system of Claim 1, further comprising a plurality of perforated ducts (30) arranged in a configuration to form a drying area within the soil (60).

11. The system of Claim 1, further comprising a drying chamber (90) configured to receive the airflow (70) after it has circulated through the perforated duct (30), wherein the drying chamber (90) is configured to dry the airflow (70) and reintroduce it into the system.

12. The system of Claim 1, wherein the pumping system (50) is introduced within the at least one perforated duct (30).

13. The system of Claim 1, further comprising an outlet pipe (34) surrounding the perforated duct (30) and airflow circulating mechanism (40).

14. A method for modifying soil (60), comprising the steps of: generating a low Relative Humidity (RH) airflow (70) with a low Relative Humidity (RH) generator (25); introducing said low RH airflow (70) into a perforated duct (30) at one end, configured to allow the airflow (70) to interact with the soil (60) moisture.

15. The method of Claim 14, wherein the step of generating the low RH airflow (70) includes increasing the temperature of the airflow (70) with a heating element (21).

16. The method of Claim 4, wherein the step of generating the low RH airflow(70) includes generating the airflow using an air compressor (41).

17. The method of Claim 14, wherein the step of generating the low RH airflow (70) includes generating the airflow using a fan (42).

18. The method of Claim 14, further comprising a step of pumping water located in the proximity of the perforated duct (30) with a submersible pump (51).

19. The method of Claim 14, wherein the step of introducing said low RH airflow (70) into the perforated duct (30) is maintained continuously achieving a relative humidity of the airflow (70) to lower than the threshold design value.

20. The method of Claim 14, further comprising a step of directing the airflow (70) after it has interacted with the soil moisture (80), to a drying chamber (90), drying the airflow (70) within the drying chamber (90) and reintroducing the low RH airflow (70) into the perforated duct (30).

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