The process of improving thick, soft and loose soils using deep soil-cement foundations in combination with sand or cemented sand impact compaction foundations.

Abstract

The process of improving thick soft and loose soils using deep soil-cement footings in combination with sand or cemented sand impact compaction footings is to address the weaknesses of DSM footings and also to increase the load-bearing capacity of the ends of single compaction footings in soft and loose soils. This system improves the mechanical behavior of the subgrade by longitudinally integrating the two types of footings. Depending on the type and thickness of the loose layers and the degree of soil consistency, four types of composite systems can be used to improve the ground, increase the bearing capacity, reduce the settlement of shallow foundations, and improve the stability of the bed in difficult coastal conditions:\n1. Sand impact compaction foundation + soil-cement foundation\n2. Cemented sand impact compaction foundation + soil-cement foundation\n3. Thick sand impact compaction foundation + soil-cement foundation\n4. Thick cemented sand impact compaction foundation + soil-cement foundation.\nThe choice of the type of system depends on the characteristics of the structure, the number of stories, and the amount of loads on the bed. It is also possible to increase the strength of the base by combining different base layers, either in the normal or cemented state.

Description

Description of the invention Title of the invention The process of improving thick, soft, loose soils using deep soil-cement foundations in combination with sand or cemented sand impact compaction foundations. Technical background of the relevant invention This invention is in the field of construction, improvement and reinforcement of loose (coastal) soils and its technical field is related to construction and geotechnics. Technical problem and stating the objectives of the invention Due to specific geological conditions, coastal areas mainly have loose soils and soft marine sediments, which face numerous problems in terms of geotechnical stability. These conditions can pose serious challenges to the implementation of infrastructure projects such as ports, docks, sea-related industries and tourism centers, as well as developed urban areas. Soil improvement, as a set of methods and technologies aimed at increasing bearing capacity, reducing subsidence and improving resistance to destructive phenomena such as liquefaction, is considered a key solution in these areas. Successful implementation of land reclamation projects not only ensures the safety and durability of coastal infrastructure, but also provides the necessary platform for attracting large-scale investments, expanding maritime transport activities, developing the tourism industry, and creating sustainable job opportunities. As a result, land reclamation in coastal areas is directly related to improving economic productivity and achieving sustainable development, and can be considered as one of the essential pillars in national and regional macro-planning. Most coastal and plain lands have two major environmental and geotechnical challenges. The presence of tidal currents, surface flooding, and the presence of aggressive sulfate and chlorine ions are among the environmental challenges, and the presence of thick, soft, loose layers including sand, silt, and clay with low safe bearing capacity, high settlement, low hardness, and potential for liquefaction are among the geotechnical challenges. Today, common improvement methods such as deep soil-cement mixing (DSM), high-pressure grouting (JG), micropiles (MP), and stone columns (SC) are preferred, although they have application limitations or technical and implementation challenges in soft coastal soils with large thickness. For example, the standard micropiles method (according to FHWA) or non-standard (common driving style), according to FHWA, are not technically justified for soft coastal and liquefied soils with large thickness, problems of thinning and also high corrosion. The stone or sand column (VF) method according to FHWA has application limitations for soft and very soft soils with bond strength less than 15 kPa due to the sagging of the upper part of the stone column and high settlement of the footing. Deep Soil Mixing (DSM) foundations are a well-known method for improving soft and saturated soils to increase their bearing capacity and reduce settlement of structures. However, the implementation of these foundations in very soft and loose soils in coastal and marine areas faces several technical challenges that limit the performance and durability of the foundations. Some of these challenges are as follows: A- Geotechnical challenges and bearing capacity: From the bearing capacity perspective, the implementation of DSM footings in saturated fine-grained soils faces two major challenges, including (a) the softness of the surrounding soil block and (b) the lack of sufficient lateral resistance at the top. Accordingly, the bearing capacity and stiffness modulus of DSM footings are low and their settlement is high, which requires a larger diameter. In addition, the difference in stiffness modulus between the footing and the adjacent soil causes stress concentration and increases the possibility of differential settlement in the surface area. Therefore, increasing the relative density or relative consistency of the upper soil layer will be of great importance in increasing the bearing capacity and stiffness modulus and reducing the settlement of DSM footings. B- Implementation challenges and technical equipment: The implementation of DSM foundations requires heavy, advanced and stable machinery. In very soft and loose soils, it is difficult to create a strong base to support the equipment and the risk of settlement or instability during operation increases. In addition, the complex rheological characteristics of coastal and saturated soils cause the mixing of cement with the soil to be uneven and the quality of the foundations to vary. Therefore, creating a dense and rigid base will play an effective role in the quality of DSM foundations. C- Hydraulic challenges: DSM footings have low permeability and consequently limited ability to quickly release pore water pressure in saturated soils surrounding the footing. This results in increased consolidation time, prolonged settlement, and the possibility of liquefaction under dynamic loading conditions. D- Chemical and durability challenges: In coastal environments, the presence of sulfate ions can cause destructive reactions with the column cementitious compounds. These reactions are mainly more severe in the superficial parts of the base, reducing the unconfined compressive strength (UCS) of the base and compromising the long-term durability of the structure. D- Economic and environmental problems: Due to the need for high cement consumption to achieve the desired strength, implementation costs increase and environmental impacts, including CO₂ emissions and coastal water pollution, become prominent. These challenges are part of the challenges experienced based on the results obtained from laboratory and field tests for soft coastal lands improved using the deep soil-cement mixing method. In fact, although there are various methods for improving soft coastal lands according to the standard, nevertheless, the use of these methods is not necessarily successful without understanding the field conditions. Attention to the application limitations according to the standard and local and international regulations, technological problems, implementation challenges, technical efficiency of the improvement method in the short and long term, the capacity and level of expertise of local contractors is of particular importance. Due to the above limitations, DSM piles alone cannot provide sufficient surface bearing capacity, good chemical resistance, and rapid drainage in soft and loose coastal soils. Also, the implementation of these piles requires a strong base and heavy equipment, which creates significant implementation limitations in coastal environments with soft soil. These challenges create a strong basis for the development of innovative methods, including DSM longitudinal composite piles with a strong surface section (including sand impact compaction piles-GICPs and cemented sand impact compaction piles-CGICPs). Over the past decade, based on these implementation challenges, the method of sand impact compaction piles (GICPs) and cemented sand impact compaction piles (C-GICPs) have been developed in the form of various domestic and foreign patents by the same inventor. On this basis, with the aim of addressing the short-term and long-term weaknesses of DSM pillars in coastal areas and thereby resolving the technical and implementation problems of projects being developed in coastal areas, the main criteria of this system include the following: 1- Using the idea of ​​a composite soil-cement foundation system (DSM) and sand or cemented sand impact compaction foundations to increase the technical efficiency and reliability of the foundations. 2- By using GICPs or CGICPs in the upper loose and soft layer, creating a dense or stiff layer in the upper part and thereby creating a solid base for heavy machinery traffic. Construction of DSM foundations, increasing the bearing capacity and reducing the settlement of the foundations, and strengthening the upper layer against liquefaction. A description of the state of the prior art and the history of developments related to the claimed invention. Deep Soil Mixing (DSM) as a geotechnical improvement technology was first developed in Japan in the 1960s and in parallel in Sweden in the early 1970s. The main objective was to improve the mechanical properties of soft, organic clay soils in port projects and offshore structures. In this method, the soil is broken up in situ by a rotary drilling tool and simultaneously mixed with a stabilizing slurry or powder (mainly cement). The chemical reaction of the cement with water and fine soil particles results in the formation of a cemented soil mass with higher shear strength and stiffness. The foundations resulting from DSM are usually implemented singly, linearly or in regular grids, and depending on the soil type and design conditions, their diameters vary between 0.6 and 1.5 m and their depths range up to more than 40 m. The development of modern drilling equipment and controlled injection systems has led to DSM being widely used today as one of the most efficient soil stabilization methods in large infrastructure projects, especially in coastal areas and areas with loose soils. The technologies and processes for constructing sand impact compression foundation systems have been registered by the author in the form of several domestic and foreign patents during the years 2014-2023. The diverse geotechnical conditions and the problems created on this basis have led to the development of technologies and the process for constructing these types of foundations. Impact compaction sand piles are constructed based on two mechanisms: (a) displacement, by creating a hole in the ground using a closed-end pipe and creating radial compaction of the surrounding soil; and (b) displacement, by opening the end of the pipe and filling it with sand material and then removing the pipe from the ground. My patents in this field include the following: The general method of constructing sand impact compaction foundations is based on the implementation of 4 main steps (first step) drilling and passing through the hard layer or surface rock fragments if necessary, (second step) driving the well-making ram into the weak soil layer, removing the middle shaft and pouring sand materials into the pipe and then removing the lining pipe and repeating this step if necessary, (third step) repeatedly driving the long penetrating hammer and feeding sand to the end of the foundation and (fourth step) implementing a wide ballast layer on the ground and tamping the foundation area with a flat hammer. In fact, replacing a volume of soil equivalent to the volume of the foundation and the vibrations caused by the repeated driving of the well-making ram and penetrating hammer and flat hammer using percussion blows causes the compaction of the sandy materials of the foundation and the soil around the foundation. Increasing the bearing capacity and modulus of soil bed reaction, reducing consolidation settlements of cohesive layers, drainage properties of foundations and soil resistance against liquefaction are among the main and technical advantages of these foundations.In addition, the lack of need for excavation in weak layers, no pollution of the workshop and the environment, no need for water, the possibility of implementation in loose and soft soils and submerged coastal lands, high speed and low cost of implementing foundations, the possibility of implementing sand foundations in loose and liquefied soil layers located below hard soil and rocky fragments, increasing the soil density around the foundations to the desired level, minimizing vibrations, and the lack of use of very heavy, bulky, and high-rise machinery due to the small area of ​​urban lands are among the implementation advantages of this method. Based on a general classification based on registered patents, depending on the geotechnical conditions of the soil layers and the type of loading, the compression foundations developed in this field can be divided into three categories: (a) sand impact compression foundations-GICPs, (b) cemented sand impact compression foundations-C-GICPs, and (c) thick sand impact compression foundations-GICMPs. Using technologies and technical equipment built and installed on a crawler excavator with an average weight of 20 tons, it is possible to construct sand impact compaction foundations in two triangular and square patterns with side lengths of 1-3 meters, foundation lengths of 3-6 meters, and foundation diameters of 45-180 centimeters. The idea of ​​combining a DSM foundation network with a conventional sand column network and its application in a soil improvement project located in India was presented in a conference paper titled below in 2022 by Vidyaranya Bandi et al. Strengthening of the Foundation Using Deep Mixing and Stone Column Techniques for Large Earth Cum Rock Fill (ECRF) Dam for an Irrigation Project In fact, the reason for using sand columns in combination with DSM foundations is due to the drainage properties of sand columns and the reduction in pore water pressure created. Sand impact compaction piles are a new technology in the field of improving the subsoil of loose, saturated soils with high liquefaction potential. This technology is designed to increase the bearing capacity, stiffness modulus and reduce seismic hazards. On this basis, the idea of ​​combining DSM piles with impact compaction piles or cemented impact compaction piles is completely different from the idea of ​​combining DSM piles with first-generation sand columns, and in the next section, the differences and similarities of these two ideas will be explained. Providing a solution to an existing technical problem along with an accurate, sufficient, and integrated description of the invention In the context of constructing medium-sized buildings (4-7 stories) in coastal areas with soft soil layers and environmental and geotechnical constraints, the use of the standard deep soil-cement (DSM) method is associated with significant technical and implementation challenges. However, due to the known effectiveness of DSM and the widespread willingness of builders and civil engineers to use this method in coastal projects, modifying and optimizing the DSM implementation structure can: A- Increase the technical efficiency of foundations and their long-term reliability, b. Provide greater confidence in the successful application of this method in difficult situations, and C- It will enable the wider development of DSM use in coastal area projects. Given the technical and operational challenges of deep soil-cement (DSM) foundations in coastal areas, including reduced bearing capacity and stiffness modulus in the upper soft layers, high settlement, limitations in supporting heavy machinery, low column permeability, and durability threats from the presence of aggressive ions, the need to modify and optimize the structure of these foundations to increase long-term efficiency and reliability is evident. Accordingly, the criteria and philosophy for combining sand or cemented sand impact compaction foundations with DSM foundations in the improvement of soft and loose soils, based on an analysis of operational and technical constraints and efforts to improve bearing capacity, reduce settlement, facilitate machinery operation, and increase chemical durability are as follows: A- Creating a resistant surface bed: Using sand impact compaction (GICP) or cemented sand (C-GICP) in the upper soft soil layer, in order to increase the relative soil density, reduce footing settlement, and facilitate the movement and stability of DSM foundation construction machinery. B- Increasing load-bearing capacity and stiffness modulus: Using DSM foundations at the design depth, with the aim of transferring deep loads to more resistant layers, reducing the difference in stiffness modulus between the column and the adjacent soil, and preventing stress concentration and differential settlement. C- Improving drainage and reducing consolidation time: Using sand or cemented sand layers in the topsoil layer to increase local permeability and accelerate the discharge of pore water pressure, which reduces consolidation settlement and reduces the risk of liquefaction. D- Increasing chemical durability: Using cemented aggregate (C-GICP) and selecting materials resistant to aggressive ions such as sulfates, in order to protect DSM columns and increase the useful life of the foundations. E- Ease of implementation and cost reduction: Creating a dense surface layer in a way that, on the one hand, creates a suitable base for machinery and, on the other hand, reduces cement consumption in DSM foundations, which contributes to both economic savings and environmental impacts. C- Flexibility of the implementation pattern: Possibility of designing different networks of foundations (parallel, cross, triangular or square) and adjusting the diameter, spacing and depth of columns according to soil conditions and loading without implementation restrictions. The overall process of constructing a composite system of sand impact compaction foundations and soil-cement foundations is based on the implementation of 6 main steps, including: (first step) implementing the soil-cement foundation from a depth of 3-6 meters to the required depth (if possible, reaching a solid subgrade), (second step) driving the well-making mandrel in the axis of the implemented foundation until reaching the top of the soil-cement foundation and removing the middle axis, (third step) pouring sand materials into the lining pipe, (fourth step) removing the lining pipe from the bed, (fifth step) repeatedly driving the long penetrating hammer and repeatedly feeding sand to the end of the foundation, and (sixth step) implementing an extensive ballast layer on the ground and tamping the foundation area with a flat hammer. Also, the overall process of constructing a composite system of cemented sand impact compaction foundations and soil-cement foundations is based on the implementation of 7 main steps, including: (first step) implementing the soil-cement foundation from a depth of 3-6 meters to the required depth (if possible, reaching a solid subgrade), (second step) driving the well-making mandrel in the axis of the implemented foundation until reaching the top of the soil-cement foundation and removing the middle axis, (third step) installing a cement slurry injection pipe in the wall of the lining pipe and pouring sand materials into the lining pipe, (fourth step) removing the lining pipe from the bed, (fifth step) repeatedly driving a long penetrating hammer and repeatedly feeding sand to the end of the foundation, (sixth step) implementing a wide layer of sand and ballast on the ground and tamping the foundation area with a flat hammer, and (seventh step) after the complete implementation of the compaction foundations within the project area and after about 2-3 weeks have passed in order to perform radial consolidation, performing pressure injection of cement slurry into the foundations. In this system, the choice of the type of compaction foundation depends on the type of the upper soil layer. If the upper soil layer is loose sand, a sand impact compaction foundation is used with three main objectives: (a) creating radial compaction for the surrounding soil block around the foundation during the foundation construction and compacting the upper soil layer bed, (b) radial drainage of the surrounding soil block around the foundation and reducing pore water excess pressures under compressive loading conditions or earthquakes, and (c) long-term stability of the foundation. If the upper soil layer is soft clay or silt, a cemented sand impact compaction foundation is used with three main objectives: (a) creating radial consolidation for the surrounding soil block around the foundation during foundation construction and increasing the relative consistency of the upper soil layer bed, (b) increasing the stiffness of the upper part of the foundation by creating cementation in the sand mass and preventing the occurrence of pothole failure and increasing the bearing capacity and reducing foundation settlement, and (c) ensuring long-term stability of the foundation. The diameter of the sand or cemented sand impact compaction foundation is at least equal to the diameter of the soil-cement foundation. In practice, it is possible to construct thick sand or cemented sand impact compaction foundations with a diameter greater than the diameter of the soil-cement foundation. In addition, in the case of constructing a wall of soil-cement foundations (sekanti foundations), it is also possible to construct thick sand or cemented sand impact compaction foundations. Explanation of shapes, maps and diagrams Figure (1-1) Schematically shows the different stages of constructing a composite system of sand impact compaction foundations and soil-cement foundations in a thick loose and soft soil bed (loose granular layer on a soft fine-grained layer), including the following steps: First and second steps: Implement the soil-cement base (304) into the soft subgrade (201) from a depth of 3-6 meters to the required depth (if possible, reaching the solid subgrade (202)) using the DSM device and the longitudinal axis of the soil-cement mixer (300) with the splitting end (302) and the mixing blades (301). Third and fourth steps: The well-drilling ram is driven along the base axis until it reaches the top of the soil-cement base using a hydraulic hammer (101) mounted on a crawler excavator. Step 5: Remove the center shaft (114) from inside the mandrel wall tube (115). Step 6: Pour sand into the manhole cover pipe using the sand discharge funnel (125). Step 7: Removing the mandrel tube. Step 8: Pounding the sand material into and to the end of the sand base (126) using a long penetrating hammer (121 and 122) and repeatedly feeding the sand simultaneously. Step 9: Apply a wide layer of sand on the composite bed and compact the bed using a compactor (124). Step 10: Complete the wide layer of sand (127) in the composite bed until the desired level is achieved. Figure (1-2) shows a longitudinal section of a wide foundation (129) and its connected columns (130) located on a composite bed consisting of an engineered embankment (128), a loose granular soil bed (200) improved using a network of sand impact compaction pads (126) with two equilateral or square triangle patterns, and a soft fine-grained soil layer (201) improved using soil-cement pads (304), assuming the formation of longitudinal composite pads. Figure (2-1) Schematically shows the different stages of constructing a composite system of cemented sand impact compression foundations and soil-cement foundations in thick soft soil beds, including the following steps: First and second steps: Implement the soil-cement base (304) into the soft subgrade (201) from a depth of 3-6 meters to the required depth (if possible, reaching the solid subgrade (202)) using the DSM device and the longitudinal axis of the soil-cement mixer (300) with the splitting end (302) and the mixing blades (301). Third and fourth steps: The well-drilling ram is driven along the base axis until it reaches the top of the soil-cement base using a hydraulic hammer (101) mounted on a crawler excavator. Step 5: Remove the center shaft (114) from inside the mandrel wall tube (115). Sixth, seventh and eighth steps: Installing the cement slurry injection pipe (131) into the wall of the lining pipe and pouring sand into the lining pipe using the sand discharge funnel (125). Step 9: Removing the mandrel tube. Steps 10, 11, and 12: Tamping the sand materials inside and to the end of the sand base using a long penetrating hammer and repeatedly feeding the sand simultaneously, implementing a wide sand layer on the composite bed and tamping the bed using a tamping bed, completing the wide sand layer (137) in the composite bed until the desired level is achieved, allowing about 2-3 weeks to pass in order to perform radial consolidation, and performing pressure injection of cement slurry into the bases (132). Figure (2-2) shows a longitudinal section of a wide foundation (129) and its connected columns (130) located on a composite bed consisting of an engineered embankment (127), a soft fine-grained soil bed (201) improved using a network of cemented sand impact compaction footings (132) with two equilateral or square triangle patterns, and a soft fine-grained soil layer (201) improved using soil-cement footings (304), assuming the formation of longitudinal composite footings. Figure (3-1) Schematically shows the different stages of constructing a composite system of thick sand impact compaction foundations and soil-cement foundations in a thick soft and loose soil bed (loose granular layer on a soft fine granular layer), including the following steps: First and second steps: Implement the soil-cement base (304) into the soft subgrade (201) from a depth of 3-6 meters to the required depth (if possible, reaching the solid subgrade (202)) using the DSM device and the longitudinal axis of the soil-cement mixer (300) with the splitting end (302) and the mixing blades (301). Third and fourth steps: The well-drilling ram is driven along the base axis until it reaches the top of the soil-cement base using a hydraulic hammer (101) mounted on a crawler excavator. Step 5: Remove the center shaft (114) from inside the mandrel wall tube (115). Step 6: Pour sand into the manhole cover pipe using the sand discharge funnel (125). Step 7: Removing the mandrel tube. Steps 8 to 12: Repeat steps 3 to 7 for the required number of compaction bases tangentially to the thick base, Step 13: Repeated thrusting of the long penetrating hammer and repeated feeding of sand to the end of the thick base. Step 14: Apply a wide layer of sand on the composite bed and compact the bed using a compactor (124). Step 15: Complete the wide layer of sand (127) in the composite bed until the desired level is achieved. Figure (3-2) shows a longitudinal section of a wide foundation (129) and its connected columns (130) located on a composite bed consisting of an engineered embankment (127), a loose granular soil bed (200) improved using a network of thick sand impact compaction pads (133) with two equilateral or square triangle patterns, and a soft fine-grained soil layer (201) improved using soil-cement pads (304), assuming the formation of longitudinal composite pads. Figure (4-1) shows the different stages of constructing a composite system of thick cemented sand impact compression foundations and soil-cement foundations in a thick soft soil bed in a schematic manner, including the following steps: First and second steps: Implement the soil-cement base (304) into the soft subgrade (201) from a depth of 3-6 meters to the required depth (if possible, reaching the solid subgrade (202)) using the DSM device and the longitudinal axis of the soil-cement mixer (300) with the splitting end (302) and the mixing blades (301). Third and fourth steps: The well-drilling ram is driven along the base axis until it reaches the top of the soil-cement base using a hydraulic hammer (101) mounted on a crawler excavator. Step 5: Remove the center shaft (114) from inside the mandrel wall tube (115). Sixth and seventh steps: Installing the cement slurry injection pipe (131) into the wall of the lining pipe and pouring sand into the mandrel lining pipe using the sand discharge funnel (125). Step 8: Removing the mandrel tube. Steps 9 to 14: Repeat steps 3 to 8 for the required number of compaction bases tangentially to the thick base, Step 15: Repeated thrusting of the long penetrating hammer and repeated feeding of sand to the end of the thick base. Steps 16 and 17: Laying the expanded sand layer on the composite bed, compacting the bed using a compactor (124), completing the expanded sand layer (127) on the composite bed until the desired level is achieved, allowing approximately 2-3 weeks to pass in order to perform radial consolidation and inject cement slurry into the thick base (134). Figure (4-2) shows a longitudinal section of a sample of an expanded foundation (129) and its connected columns (130) located on a composite bed consisting of an engineered embankment (127), a soft fine-grained soil bed (201) improved using a network of thick cemented sand impact compaction footings (134) with two equilateral or square triangle patterns, and a soft fine-grained soil layer (201) improved using soil-cement footings (304), assuming the formation of longitudinal composite footings. Figure (5-1) shows a longitudinal section of a wide foundation (129) and its connected columns (130) located on a composite bed consisting of an engineered embankment (127), a loose granular soil bed (200) improved using a composite network of thick sand impact compaction footings (133) and sand impact compaction footings (126) interspersed with two equilateral or square triangle patterns, and a soft fine-grained soil layer (201) improved using soil-cement footings (304), assuming the formation of longitudinal composite footings. Figure (5-2) shows a longitudinal section of a wide foundation (129) and its connected columns (130) located on a composite bed consisting of an engineered embankment (127), a loose granular soil bed (200) improved using a composite network of thick sand impact compaction piers (133) at the base of the columns and sand impact compaction piers (126) in the space between the thick piers with two equilateral or square triangle patterns, and a soft fine-grained soil layer (201) improved using soil-cement piers (304), assuming the formation of longitudinal composite piers. Figure (6-1) shows a longitudinal section of a wide foundation (129) and its connected columns (130) located on a composite bed consisting of an engineered embankment (127), a soft fine-grained soil bed (201) improved using a composite network of thick cemented sand impact compaction piers (134) and cemented sand impact compaction piers (132) interspersed with two equilateral or square triangle patterns, and a soft fine-grained soil layer (201) improved using soil-cement piers (304), assuming the formation of longitudinal composite piers. Figure (6-2) shows a longitudinal section of a wide foundation (129) and its connected columns (130) located on a composite bed consisting of an engineered embankment (127), a soft fine-grained soil bed (201) improved using a composite network of thick cemented sand impact compression piles (134) at the base of the columns and cemented sand impact compression piles (132) in the space between the thick piles with two equilateral or square triangle patterns, and a soft fine-grained soil layer (201) improved using soil-cement piles (304), assuming the formation of longitudinal composite piles. Figure (7-1) Longitudinal cross-section of the main components of the well-making and hammering mandrels, including the following parts: 101= Hydraulic hammer. 103= Short steel shaft of the hammer to transfer the impact from the hammer to the punch. 104= Flat steel disc with double-stepped edge. 114= Steel shaft of the middle axle. 115= Wall pipe. 116= Two rings welded to the steel shaft for transporting the center axle. 117= Steel ring stiffening the end of the wall pipe. 118 = Steel plates connected to piece 114 and piece 119 to make the conical end of the middle shaft. 119= Steel shell of the conical end of the middle axis. 120= Cables connected to the hammer to move the mandrel components. Figure (7-2) Enlarged details of the upper part of the well-making mandrel and the rammer, including parts 101, 103, 104, 114, 115 and 120 and the following parts; 105= Four rings welded onto the mandrel tube for carrying it. 106= Vertical stiffening steel plates around the tube, connected (welded) to the horizontal ring and the wall tube. 107= Steel plates stiffening the pipe wall, welded to the pipe wall and between the vertical stiffening steel plates and the horizontal ring. 108= Horizontal steel ring to harden the edge of the wall pipe against impact from the hammer. 109= Complete steel ring connected (welded) to the wall tube to hold the center axle during movement. 110= Incomplete steel ring attached (welded) to the upper cylinder (piece 111) of the center axle to rest on piece 109 during movement. 111= Steel ring on the outer wall of the upper cylinder of the middle axle. 112= Four shear steel plates for load exchange between two pieces 111 and 113. 113= Steel ring of the inner wall of the upper cylinder of the middle axle and connected to the middle shaft (part 114) and four shear steel plates (part 112). Figure (7-3) Cross-section of the upper part of the well-making mandrel, including parts 109 and 111 to 115. Figure (7-4) Enlarged details of the end of the well-making mandrel, including parts 114 and 117 to 119. Figure (8-1) Three-dimensional view of the well-making mandrel and the hammer mandrel, including parts 101, 103, 104, 115, 119, and 120. Figure (8-2) Enlarged details of the upper part of the well-making mandrel and the hammer mandrel, including parts 101, 103 to 108, 115 and 120 and the following parts; 102= Two rings connected (welded) to the hydraulic hammer to lift the various components of the mandrel. Figure (9-1) Longitudinal cross-section of the manhole casing pipe including parts 115 and 117; Figure (9-2) Enlarged details of the upper part of the mandrel casing pipe, including parts 105 to 109 and 115; Figure (9-3) Enlarged details of the end of the mandrel casing pipe, including parts 115 and 117; Figure (10-1) Longitudinal cross-section of the center axis of the well-making mandrel, including parts 112, 114, 116, 118, and 119; Figure (10-2) Enlarged details of the upper part of the center shaft of the well-making mandrel, including parts 111 to 114; Figure (10-3) Three-dimensional view of the center shaft of the wellbore including parts 110 to 114, 116 and 119; Figure (10-4) Enlarged detail of the upper part of the center shaft of the well-making mandrel, including parts 110 to 114; Figure (10-5) Enlarged detail of the end of the center shaft of the well-making mandrel, including parts 114 and 119; Figure (11) 3D view of the long penetrating hammer including the following parts; 121= Long steel shaft to transmit blows from the hydraulic hammer to part 122. 122= A steel cylinder with two beveled ends attached to the end of a long shaft. Figure (12) Three-dimensional view of the ramming bed including the following parts; 123= Short steel shaft to transmit blows from the hydraulic hammer to part 124. 124= Steel disc with a beveled edge attached to a short steel shaft. Figure (13) shows the overall block diagram of the process of constructing a composite system of sand impact compaction foundation and soil-cement foundation in thick two-layer soil beds (loose sand layer on soft clay layer). Figure (14) shows the overall block diagram of a composite system of cemented sand impact compaction foundation and soil-cement foundation in thick soft fine-grained soil beds (silty or soft clay layer). Figure (15) shows the overall block diagram of the process of constructing a composite system of thick sand impact compaction base and soil-cement base in two-layer soil beds (loose sand layer on a thick soft clay layer). Figure (16) shows the general block diagram of a composite system of thick cemented sand impact compaction base and soil-cement base in thick soft fine-grained soil beds (silty or soft clay layer). A clear and precise statement of the advantages of the claimed invention over prior inventions. The features and advantages of the process of improving thick soft and loose soils using a combined system of deep soil-cement foundations (DSM) and sand-impact compaction foundations (GICPs) or cemented sand (C-GICPs) compared to soil improvement based solely on compaction foundations or soil improvement based solely on soil-cement foundations are as follows: 1- In the case of constructing a building on thick, soft, and loose coastal soil layers, with the increase in the number of floors and the importance of the building, the priority for selecting the improvement system is, respectively, the method of sand impact compression foundations (GICPs), cemented sand impact compression foundations (C-GICPs), deep soil-cement foundations (DSM), a combined system of GICPs and DSM, and a combined system of C-GICPs and DSM. On this basis, assuming constant environmental and geotechnical conditions, by choosing a combined system of GICPs and DSM, a foundation with greater strength and reliability in static and seismic conditions can be achieved compared to the DSM system. 2- In two-layer soil beds (loose sand layer on thick soft clay layer) improved using DSM foundations, the surrounding soil block around the foundations in the upper and lower parts remains loose and soft, respectively, due to which the technical efficiency of the foundations decreases, especially in seismic conditions. While using composite GICPs and DSM foundations, the surrounding soil block around the GICPs and, consequently, the upper sandy soil layer becomes fully compacted. 3- According to paragraph 2, if a system of DSM footings is used, the technical efficiency of the footings will decrease due to the following reasons: (a) high soil looseness around the footing and increased stress concentration on the footing heads, (b) low bearing capacity of the footings due to reduced lateral pressure resistance around the footing, (c) high slenderness of the footings and the possibility of serious damage to them in seismic conditions, (d) failure to successfully form a cement-sand bond in the upper part due to the presence of tidal currents during cement setting, (f) the effect of aggressive magnesium sulfate ions on the footings and an effective reduction in reliability can occur. On this basis, eliminating DSM footings in the sand layer and creating a desirable relative density of the sand layer in the area under the foundation of the building by implementing a network of GICPs footings will eliminate all the destructive effects mentioned above. 4- According to paragraph 2, the use of GICPs bases in the upper sand layer leads to substantial control of the liquefaction potential in this layer, while not using these bases and relying solely on DSM bases leads to a reduction in the liquefaction potential. 5- In soil beds consisting of layered clay layers improved using DSM foundations, the surrounding soil block around the foundations in the upper and lower parts remains soft, respectively, which reduces the technical efficiency of the foundations, especially in seismic conditions. While using composite GICPs and DSM foundations, the surrounding soil block around the GICPs foundations becomes radially consolidated and their relative consistency increases during the implementation of the foundations. Cementing GICPs foundations can lead to an increase in the bearing capacity and modulus of rigidity and a decrease in the settlement of these foundations. 6- According to paragraph 5, the use of GICPs in the upper clay layer eliminates the consolidation settlement of this layer, thereby increasing the safe bearing capacity of the bed compared to the DSM improvement system. 7- Based on the economic evaluation, the cost of implementing the two composite foundation systems GICPs + DSM and C-GICPs + DSM, despite having significant technical advantages, may be up to 10% higher than the cost of implementing the DSM improvement system. This slight increase in cost is negligible compared to the indirect economic benefits resulting from increasing the lifespan of the building, or not using a deep foundation system, and thereby significantly reducing improvement costs. 8- In composite systems, it is possible to combine different patterns (parallel, triangular, square or cross) and adjust the spacing, diameter and depth of the foundations according to soil conditions and loading well. While in independent GICPs or DSM systems there are significant limitations. 9- In composite systems, after improving the bed, due to the creation of a solid and hard bed, it is possible to move various machines to implement the engineering embankment at different times. While in the independent DSM system, this capability does not exist and there are implementation challenges, including the presence of looseness and softness of the bed between the foundations and the serious possibility of damage to the brittle soil-cement footings. Description of at least one implementation method for implementing the invention To use this invention in any implementation project, four basic steps are required as follows: First stage: Geotechnical assessment and design  Conducting geotechnical studies of the desired area through drilling, stratification, and determining the thickness and type of each layer, conducting necessary field tests such as SPT or CPT at even or odd depths, conducting various laboratory tests at even or odd depths, and determining the physical, mechanical, consolidation, and chemical properties of the soil. Identifying problematic soil layers and conducting geotechnical analyses Technical and economic evaluation of various soil improvement methods appropriate to the technical conditions of the project and selection of the winning method Determine the grid pattern, spacing, diameter, and depth of DSM foundations and GICPs or C-GICPs compression foundations according to building loading and soil conditions. Second stage: Implementation of DSM foundations within the specified depth range Creating a suitable surface bed through engineered embankment or implementing sand impact compaction foundations Implementation of DSM foundations by penetrating and mixing soil with cement or other stabilizers within the specified depth range according to the design pattern (parallel, square, triangular or cross). Stage Three: Implementation of sand or cemented sand impact compaction foundations Initial implementation of GICPs foundations at the site of DSM foundations Construction of the first layer of the engineering embankment simultaneously with the construction of compaction foundations and the infiltration compaction of the foundations and the bed surface. Enough time (2-4 weeks) for radial drainage of the surrounding soil block Completion of the network of compaction bases Injection of compression bases if necessary The required time period is up to 28 days. Step 4: Quality control and performance evaluation Conducting compression loading tests on the bed between the piers and composite piers and determining the bearing capacity, stiffness modulus, and settlement of the piers after the implementation of GICPs, C-GICPs, and DSM piers. Conducting SPT tests on the surrounding soil block around the foundations to determine the physical and mechanical properties of the soil after improvement in order to perform various geotechnical analyses. If needed, further modification and reinforcement based on test results Completion of engineered embankment layers Creating a strong and resistant base ready for concrete placement for the foundation and foundation of the building Explicit mention of the industrial application of the invention The process of improving thick, soft and loose soils using a composite system of deep soil-cement foundations and sand or cemented sand impact compaction foundations can have the following main applications, depending on the environmental and geotechnical conditions of the project site: 1- Building on loose and soft soils: In order to increase the bearing capacity and modulus of soil reaction and reduce the settlement of the foundation of short and medium-sized buildings. 2- Port and marine projects: Stabilizing the bed of piers, breakwaters, anchorages, and other marine-related structures that are built in soft coastal soils. 3- Transportation infrastructure: Improving the subgrade of roads, bridges, and entrance ramps to ports and airports that are located on soft, saturated soil. 4- Industrial and power plant structures: Creating stable foundations for factories, energy facilities, and pipelines in areas with loose soils and high liquefaction. 5- Developing coastal and recreational tourism: Providing a resilient base for hotels, tourist complexes, recreational piers, and coastal walking paths on soft and loose ground. 6- Application in soil reinforcement and rehabilitation projects: Improving the bed of existing structures that have subsided or reduced stiffness modulus over time, without the need for extensive excavation or complete cessation of activities. This invention enables industrial use in a variety of construction and infrastructure projects due to its ability to simultaneously reinforce both surface and depth, ease of implementation, flexibility of the foundation network, and high chemical durability.

Claims

Claim What is claimed: Claim 1) The process of improving thick, loose soils in coastal areas using a composite system including deep soil-cement foundations and sand impact compaction foundations includes the following steps: Step 1: Implementing soil-cement foundations from a depth of 3-6 meters until reaching the resistant subgrade, Step 2: Driving the well-making mandrel in the axis of the implemented foundation until reaching the top of the soil-cement foundation and removing the middle axis, Step 3: Pouring sand materials into the lining pipe and removing the pipe from the bed, Step 4: Repeated driving of the long penetrating hammer and repeated feeding of materials to the end of the foundation, Step 5: Implementing an extensive ballast layer on the ground and tamping the foundation area with a flat hammer. Claim 2) According to claim 1, the process in conditions where cemented sand impact compression foundations are used includes the following additional steps: - Installing a cement slurry injection pipe in the wall of the lining pipe and pouring cemented sand materials, - After the compression foundations are fully implemented and 2-3 weeks have passed for radial consolidation, performing pressure injection of cement slurry into the foundations. Claim 3) According to claim 1, the process in the case where thick sand impact compaction bases are used in combination with soil-cement bases comprises performing steps 1 to 4 as many compaction bases as required tangentially in the thick base. Claim 4) According to claim 2, the process in which cemented thick sand impact compaction bases are used in combination with soil-cement bases, comprises performing steps 1 to 4 for the required number of compaction bases tangentially in the thick base and injecting cement slurry after radial consolidation. Claim 5) According to claims 1 to 4, the process is carried out in conditions where compacted sand or cemented sand foundations are used, in order to increase the density or relative consistency of the upper soil layer, provide a resistant substrate and reduce settlement and stress concentration of the soil-cement foundations. Claim 6) According to claims 1 to 5, the process is carried out in conditions where compacted sand or cemented sand foundations are used, in order to improve drainage and reduce pore water pressure in the upper layer and around the soil-cement foundations, so as to reduce consolidation time and reduce the risk of liquefaction under dynamic loading conditions.

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