Various tests and surveys

Screw Weight Penetration Test (SWS Test / Old Swedish Sounding Test)

The Screw Weight Penetration Test (SWS) is a quick and accurate way to determine the strength of the ground.
Because it is a relatively small-scale test, it can be completed in about half a day. While it is suitable for investigating in confined areas, if there are large stones or debris, the test must be conducted again at a different location.

A special rod is inserted into five points at the four corners and the center of the proposed construction site, and based on the sinking of the rod, the hardness, softness, and compaction of the ground are checked to evaluate the strength of the ground.
There are three types of tests: "manual," "semi-automatic," and "fully automatic," all of which are capable of determining resistance values up to a depth of 10 meters.

Boring Standard Penetration Test

The Boring Standard Penetration Test is a test that can be used to drill through hard ground and deep subterranean support layers.
The test may take several days to complete because it requires a working space of approximately 5m square and a 5m-high yagura.

A hammer with a mass of 63.5 kg is dropped freely from a height of 76 cm, and the number of blows until the sampler penetrates 30 cm is recorded to calculate the strength of the ground; the ground bearing capacity can be calculated by determining the N value, and soil properties and strata can also be determined by sampling soil from deeper layers.

Note that when using a borehole to investigate the groundwater level, the test must be conducted using "waterless drilling," in which no water is used.

Flat Plate Loading Test

The "Plain Plate Loading Test" is a test to confirm the bearing capacity, coefficient of reaction, and settlement of the ground directly under the foundation. Since the test is performed by applying a load directly to the ground, it provides very reliable test results.
Vibration and noise are minimal, and work time can be reduced to about 5 hours. However, since large heavy equipment is used, a large work space is required, and ground investigation below a depth of 6 m cannot be performed.

A loading plate with a diameter of 30 cm is placed on the leveled ground, and a jack, strut, and displacement meter are set as loading equipment to conduct the test. A vertical load is applied and the amount of settlement is measured to determine the bearing capacity of the ground.
The test is terminated when one of the following conditions is met: "the planned maximum loading pressure is reached," "ground failure is observed," or "the amount of settlement reaches 10% of the loading plate diameter.

Pile Loading Tests in Photovoltaics

When constructing a structure, this test confirms the resistance of the pile foundation through appropriate loading tests. The following three types of investigations are conducted based on the pile loading tests conducted by The Japanese Geotechnical Society (JGSE).

＜Push-in Test＞

This is a loading test to confirm that a pile has resistance to stress in the push-in direction. The stress acting on the pile in the push-in direction does not exceed the bearing capacity of the pile. An oil jack is installed with the weight of the backhoe aligned with the pile, and a push-in load is applied to the pile using the reaction force of the heavy equipment.

＜Pull-out Test＞

This is a loading test to confirm that the pile is resistant to stress in the pull-out direction. The short-term stress acting on the pile in the pull-out direction does not exceed the short-term allowable pull-out resistance of the pile.
A steel rod is placed at the head of the loaded pile, and the steel rod is connected to a center hole jack attached to a lifting jig. The jig is suspended by the arm of a backhoe, and the center hole jack is used to apply a pulling force to the loaded pile.

＜Horizontal Test＞

This is a loading test to confirm that the pile is resistant to horizontal stress. The test confirms that the short-term horizontal stress acting on the pile does not exceed the design limit horizontal resistance calculated using the coefficient of horizontal ground reaction.
After attaching a steel rod to the head of the loaded pile, a suspension jig is placed horizontally and the steel rod is connected to a center hole jack. The jig is fixed to the bucket hook of the backhoe, and the center hole jack applies horizontal force to the load pile.