Soil Stabilization and Dynamic Compaction for Load-Bearing Raft
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Solution Overview
Problem
Conventional methods for modifying geotechnically unsuitable soils, such as piling, soil stabilization, and dynamic compaction, are either costly, time-consuming, or environmentally impactful, and none can completely eliminate the need for piling or 'dig and dump' techniques, while existing wisdom suggests that soil stabilization and rolling dynamic compaction are competing processes.
Innovation Solution
Combining soil stabilization and rolling dynamic compaction in a synergistic method that involves excavating, stabilizing, compacting, and consolidating soils to create a load-bearing layer, using treatments like lime to reduce moisture content and applying rolling dynamic compaction with adapted techniques to achieve extensive compaction and consolidation, thereby eliminating the need for piling and 'dig and dump' methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If piling is used to transfer loads to underlying strata, then load-bearing capability is improved, but construction time and cost increase significantly
Solution Approach 1:
The patent changes the physical and chemical parameters of the soil in place by applying stabilizing agents (lime, cement, fly ash) to modify soil properties such as moisture content, plasticity, and shear strength. This transforms weak soils into load-bearing capable soils without requiring deep piling, thereby reducing construction time while maintaining structural strength
Solution Approach 2:
The patent extracts and removes the geotechnically unsuitable soil layers that cannot bear loads, and replaces them with imported fill materials that have been pre-stabilized or can be easily compacted to achieve required bearing capacities, avoiding the time-consuming process of deep piling
2Quantity of substance
If soil stabilisation is applied to modify soil properties, then moisture content is reduced, but construction time increases
Solution Approach 1:
The patent applies soil stabilisation treatments to the excavated soil before backfilling the excavation. By pre-stabilizing the soil off-site or in controlled conditions, the moisture content is reduced and soil properties are improved before the backfilling operation, thereby minimizing the time required for on-site stabilization and accelerating the overall construction schedule
Solution Approach 2:
The patent implements continuous soil stabilisation operations during the excavation and backfilling process, rather than completing all stabilization before backfilling. This continuous approach allows parallel operations to proceed simultaneously, reducing total construction time while achieving the required moisture reduction and soil improvement
3Length of stationary object
If rolling dynamic compaction is applied to compact soil, then compaction depth is improved, but soil structure may be damaged
Solution Approach 1:
The patent applies rolling dynamic compaction selectively to specific zones where deep compaction is required, rather than uniformly across the entire site. By targeting only the areas and depths where unsuitable soils are present, the method achieves necessary compaction depth while minimizing disruption to soil structures in areas where shallow compaction or other methods are sufficient
Solution Approach 2:
The patent divides the compaction process into multiple passes with varying roller weights and drop heights, and segments the treatment area into zones based on soil conditions and required compaction depths. This segmented approach allows optimization of compaction parameters for each zone, achieving deep compaction where needed while preserving soil structure in less critical areas
4Ease of manufacture
If geotechnically unsuitable soils are left unchanged, then construction cost is reduced, but differential settlement occurs
Solution Approach 1:
The patent applies chemical and physical treatments to change the parameters of geotechnically unsuitable soils, including moisture content reduction through stabilizing agents, plasticity modification, and shear strength enhancement. These parameter changes transform the soil into a more uniform and stable material that resists differential settlement, providing a cost-effective alternative to complete soil replacement
Solution Approach 2:
The patent performs preliminary soil stabilisation and compaction operations before construction begins, addressing potential settlement issues in advance. By pre-treating the soils to achieve uniform properties and adequate bearing capacity, the need for expensive settlement mitigation measures during or after construction is eliminated, achieving both cost reduction and settlement uniformity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This combined method reduces the risk of differential settlement, achieves significant cost savings, and minimizes environmental impact by creating a uniform, load-bearing soil mass that supports construction without the need for piling, leading to shorter construction times and reduced environmental impact.
Implementation Method 1
The stabilisation process typically involves treating a hydrated clay soil with an anhydrous material such as lime, so as to reduce the water content of the soil
Implementation Method 2
treating a hydrated clay soil with an anhydrous material such as lime, so as to reduce the water content of the soil, and to initiate a chemical reaction resulting in modification of the chemical structure of the soil
Implementation Method 3
Dynamic compaction (DC) improves the mechanical properties of the soil by repeated application of very high intensity impacts to the surface, achieved by dropping a weight across the surface to be compacted
Implementation Method 4
The potential energy is thus converted into kinetic energy, which in turn is transferred to the soil when the apex reaches the lowest point of its cycle upon impact with the surface of the ground
Data Source
Figure 1
Figure 2
Figure 3~6
AI summary
A method of modifying geotechnically unsuitable soils (21) at a site (20) so as to render the site (20) capable of bearing a load (30) comprises steps involving soil stabilisation treatment and rolling dynamic compaction (42). A portion (40) of the site (20) is excavated down to a pre-determined depth x. Both the excavated site (40) and the soil excavated therefrom are subjected to soils stabilisation treatments, before the treated excavated soils is backfilled in layers (43), and subjected to both standard compaction (45) and rolling dynamic compaction (42). The result is a raft (32) of modified soils capable of supporting bearing pressures associated with traditional housing foundations (33, 35). The need to drive piles (25) into deep strata (24) with load-bearing capabilities, or to use other costly or environmentally unsound techniques to address the issue of geotechnically unsuitable or contaminated soils is thus avoided. The use of modified soil (32) to backfill the same site (40) from which it was excavated results in major costs savings and reduced environmental impact due to a substantial reduction in the number of lorry movements required, as compared to conventional "dig and dump" techniques.