Understanding changes within a slope, from below ground.
After rainfall, there are few ways to know continuously what is happening inside an individual slope. SAND-X is developing a sensing device that continuously measures changes in subsurface conditions such as soil moisture and water pressure.
What happens inside a slope is difficult to see
Even under the same rain, ground conditions differ from slope to slope. Subsurface moisture and water pressure cannot be seen from the surface, so what is happening inside each slope after rain remains hard to know from above ground.
- 01 Rain falls
- 02 Water infiltrates
- 03 Subsurface moisture and pore pressure change
- 04 Captured from below ground
- 01 Rain falls
- 02 Water infiltrates
- 03 Subsurface moisture and pore pressure change
- 04 Captured from below ground
Static risk locations and dynamic conditions
“Where could be at risk” and “what is at risk right now” are different questions. Layering current subsurface conditions onto the risk locations shown by existing information adds to what decisions can be based on. It does not replace static information.
Why we measure water below the surface
Changes in slope condition are related to subsurface moisture and water pressure. As rain infiltrates, water content and pore water pressure change, altering the forces that hold soil particles together and affecting conditions within the slope. Rather than relying on surface rainfall alone, we aim to capture what is actually happening below ground.
- Soil particle
- Pore water
- ↕Inter-particle forces
- Rainfall
- Infiltration
- Water & pressure change
- Slope conditions change
Scope
Technical studies and prototyping are focused on natural slopes and steep slopes, including the surface layers of slopes managed under sabo (sediment control) programmes. We believe the same way of measuring can extend to other slopes and earthworks where rain and subsurface water affect their condition.
Current focus
Possible extensions
Device overview
We are developing a pile-type sensing device that continuously measures subsurface moisture and water pressure (the causes of changes in condition) together with tilt and vibration (their effects), at the same place and the same time, in a single pile.
Planned measurements
Planned structure
- Above ground
- Power generation and communication
- Below ground
- Installed about 1 m deep, measuring at several depths
From the field to the cloud.
Data captured below ground is sent to the cloud, where it is processed, analysed and visualised. Changes in condition are notified to slope managers. The data goes to those who manage the slope; it is not a substitute for evacuation information.
- Slope
- Pore water pressure
- Volumetric water content
- Tilt
- Acceleration
- Data sent from the above-ground unit
- Data reception
- Device control
- Data normalisation
- Open data analysis
- View conditions on the web
- Alerts by email, SMS or phone
- 01 SITESiteSlope
- 02 SENSINGSensingPore water pressure, volumetric water content, tilt, acceleration
- 03 COMMUNICATIONCommunicationData sent from the above-ground unit
- 04 CLOUDCloudData reception, device control
- 05 ANALYSISProcessing & analysisData normalisation, open data analysis
- 06 VISUALISATIONVisualisationView conditions on the web; alerts by email, SMS or phone
What can be captured
Sensing has limits in both depth and horizontal coverage. Field testing will establish which phenomena — shallow slope failure, landslide, debris flow or others — can be captured, and to what degree.
- Measured zone
- Possibly measurable
- Beyond direct reach
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Depth limits
With installation at about 1 m, direct measurement is limited to the shallow zone.
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Horizontal placement
Ground is heterogeneous, and a single measurement point does not necessarily represent the whole slope. Placement method and density will be verified.
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Deeper slip surfaces
Moisture and water pressure at depth cannot be measured directly. Displacement such as tilt and acceleration may reveal changes in condition; this will be verified.
Potential uses of the data
Beyond detecting anomalous trends in future, we are exploring the value of this data for existing slope management and civil engineering decisions. The aim is to add to the information available for decisions, not to automate them.
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Measured inputs for slope stability analysis
Using measured rather than assumed values in analysis.
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Continuous slope monitoring
Tracking subsurface conditions over time, including before and after rainfall.
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Monitoring after works
Continuously checking the effect of countermeasure works and subsequent changes.
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Maintenance management
Informing inspection and maintenance priorities.
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Detecting anomalous trends in future
Target phenomena and conditions will be defined through testing.
Current development stage
The sensing device is being prototyped; measurement and field testing lie ahead. We will adapt PoC units to field conditions, with joint verification with partners in view. We are looking for partners for field trials to establish whether the device can be installed on site, how reliable communication is, and how measurements relate to changes in slope condition.
- Technical studyCompleted / ongoing
- PrototypingCurrent
- Evaluation
- Field testing
- PoC
- Deployment
Talk to us about research and technical collaboration on slope sensing.
We welcome conversations with municipal and prefectural governments, infrastructure operators, universities and research institutes, and construction and disaster risk management companies about research and technical collaboration and future field testing.