There are many projects with Smart Solo in engineering geophysical survey, among which those using microtremor survey methods can be referenced.
Our products – SmartSolo, which are the world’s first smart seismic senor, have been successfully applied in many engineering geophysics projects over the past few years. As one of the important application scenarios of our product, the microtremor survey is worth giving attention.
So, what are microtremors, and why can they stand out among many exploration methods?
Microtremor is a kind of complex vibration phenomenon in nature, which is composed of body wave and surface wave, and the energy of the surface wave is exceeding more than 70% of total energy。The microtremor survey mainly uses the seismometer array to detect the ‘noise’ from the ground, with the most common array shapes being circular, triangular, cross, or linear. The dispersion characteristics of the surface wave can be obtained from the acquired microtremor data, and the dispersion curve and H/V curve can be calculated and inverted. As a result, the shear wave velocity model and the predicted lithology of the formation can be obtained.
At present, SmartSolo products have been used to carry out several microtremor surveys in different urban rail-transit construction projects and have received a lot of attention. Compared with other engineering geophysical exploration methods, it has the following four advantages:
- No damage to underground structures and pipelines.
- Not limited to the site location, with strong anti-interference ability.
- Convenient to conduct survey, with high efficiency at low cost.
- Environmentally friendly.
Here we describe how those projects are implemented in detail：
Stability monitoring at airpor
Shield tunneling beneath an airport runway may cause the delamination and voids between the pavement and the tunnel. The MSM could be used to detect where there is a hidden cavity under the runway and its location and size.
Lagging settlement monitoring: monitor the stratum stability and deformation after the shield tunneling machine passes through. MSM will detect and alert the property owner of the existence of delamination or cavity caused by sand and soil loss.
Construction safety risk Investigation
1、Dynamic monitoring of subgrade and subsurface stratigraphic changes;
2、Investigate the hidden voids below the road surface;
3、Detect the delamination caused by sand and stone loss below the road surface;
Shield tunneling through the landmark building, the geological risk of shield tunneling interval is detected and investigated by means of microtremor survey method. There is no drilling, no dust, no noise, and the construction risk of shield tunneling is effectively eliminated while the construction task is completed with high quality.
Poor geological body detection:
Karst feature detection in Shenzhen metro line
The prediction of cavity based on a microtremor survey is highly consistent with the geological drilling, which makes up for the lack of geological information between boreholes.
After the shield tunneling machine passes through the karst area, we invert the data from the microtremor survey to unveil the geological information, and to locate the karst cave precisely.
Other than the accurate positioning of karst caves, the plane distribution of cavities can be also determined by setting up different shapes of seismometer array.
Detection and positioning of municipal pipelines:
- Probe the size and direction of the pipelines;
- Determine the absolute position and relative position of the underground pipelines.
Although the engineering geophysical projects are result-oriented, an efficient, simple, and convenient geophysical exploration method, and using efficient and stable equipment are both important and indispensable. We are looking forward to bringing more practical cases and creating greater economic value for the industry.