Ref 2.) Details of the Blue Heaven 1-1 (BH1-1) project on a 100-rai artificial island with a base of earthen mounds with a radius of 150 meters and a height of 15 meters (pancake shape). A key highlight is the steep slope of the mound's shoulders, reaching 60 degrees, which shares a sloping surface area for building townhouses/3-story single-family homes totaling approximately 10.01 rai.

This 60-degree slope is classified in geotechnical engineering as a "Steep Reinforced Slope," which natural soil or sand cannot support on its own (normal sand resting angle is only 30-35 degrees). Therefore, its application for creating earthen mounds and preventing landslides at the level of a mega-project requires the systematic integration of structural engineering and ground cover systems as follows: [1, 2]

1. Water Management System

Rainwater is the culprit that increases soil weight and reduces the cohesion between soil masses. For a three-tiered circular slope with a total walkway length of over 3.5 kilometers, water must be blocked as follows: [1]

Concentric Interceptor Drains System:

Critical point: A large, flat, pancake-top slope of 36-39 rai with a 3 rai pond will be the area receiving a massive amount of rainwater.

Method: Concrete drainage trenches must be constructed around the perimeter of the slope to intercept all rainwater and prevent it from flowing down to the third tier. A vertical chute drain should be hidden next to the 6-meter wide golf cart ramp to channel water directly into the circular moat around the island.

Subsurface Drainage and Pressure Reduction:

Critical point: Saturated soil will create lateral pressure that will cause the house and walkway to collapse.

Method: For every tier cut to create a 4-6 meter wide walkway, perforated pipes wrapped in geotextile must be placed under the walkway soil layer to trap water seeping from above and drain it out through 'emergency drainage' (weep holes) to the outside. [1]

2. Structural Soil Stabilization

Because a slope of up to 60 degrees is required to increase usable space on top, the internal structure of the slope must be 100% stable: [1]

Geogrid Reinforced Soil Slope:

During the layer-by-layer compaction phase, a Steel Plastic Geogrid or high-tensile polymer mesh sheet must be laid. Spread flat along the deep soil layers extending into the mound to act as "strong anchoring pins" to increase shear strength and prevent the soil mass from sliding apart [1, 2, 3, 4, 5].

Soil Nailing & Micro-Anchors System:

For the 10.01 rai slope area that will support the weight of row houses and single houses, the foundation and intersection points of the sloping structure must use the Soil Nailing technique, drilling and inserting rock anchors deep into the core of the compacted soil to act like nails securing each step of the sloping structure to the central anchor [1].

Protecting the Slope Surface with Three-Dimensional Honeycomb Mesh (Geocell / Metal Mesh Face):

On the 60-degree sloping surface with a slope length of 17.32 meters, the slope surface soil is easily eroded by wind and rain. It must be covered with an HDPE Geogrid Chamber (Geocell) which has a three-dimensional honeycomb structure. Lock the black soil or planting material in place on the 60-degree slope, preventing it from eroding and accumulating below [1, 2, 3].

3. Planting ground cover for long-term stability (Vegetation & Bio-Engineering)

Green engineering will help reduce the carbon footprint and enhance the aesthetics of the project in line with its Circular Economy concept:

[Rainfall impact] --> [Hydroseeding system / Coconut fiber netting] --> Prevents short-term soil erosion | v [Dense vetiver grass root penetration] --> Helps stabilize soil molecules 3-5 meters deep in the long term.

High-pressure seed spraying with water-retaining material (Hydroseeding with Tackifier):

On a 60-degree slope, normal planting is very difficult. A Hydroseeding machine is needed to spray a mixture of grass seeds, fertilizer, water-retaining wood pulp (mulch), and tackifier to firmly adhere the material to the slope. This involves mixing in fast-growing plants like millet to create a root network that protects the soil surface within the first 1-2 weeks [1, 2].

Vetiver Grass - Natural Root Structure for Deep Soil Fixation:

Vetiver grass should be planted in rows along the first, second, and third layers of pedestrian walkways. The roots of vetiver grass, which penetrate 3-5 meters straight into the soil, act like "natural piles" (living soil nails), helping to firmly anchor the 60-degree slope in the long term [1, 2].

Coir Geotextile with Legumes:

In the honeycomb mesh, mix in seeds of slow-growing but strong-rooted legumes such as Centrosema or Calopogonium, along with covering with natural coconut fiber mats (coir mat) to help retain moisture and protect against impact from rainwater during the first 3-6 months of plant growth [1, 2].