1. Setting-out of foundation trench excavation sideline and leveling of foundation pit

1. Setting-out of foundation trench excavation sideline

Before foundation excavation, measure the dimensions of excavation sideline from the central pile to both sides according to the width of foundation trench and the dimensions of slope at the top of foundation detail drawing, and mark them properly; Then, a thin line is drawn between the marks at both ends of the foundation trench, and the edge of the foundation trench is sprinkled with white ash on the ground along the thin line, and excavation is carried out according to this gray line during construction.

2. Leveling of foundation pit

In order to control the excavation depth of foundation trench, when the excavation of foundation trench is close to the trench bottom, a horizontal pile which is 1.3~1.5m higher than the design elevation of trench bottom shall be laid on the trench wall from the corner every 3~5m as the basis for excavation depth, leveling the trench bottom and laying foundation cushion. Generally, horizontal piles are laid out with a level according to the+/-1 mark or the elevation of the top surface of the gantry.

Example:

The design elevation of the trough bottom is -1.711m, and if you want to survey a horizontal pile 1.511m higher than the design elevation of the trough bottom, first place a level in an appropriate place on the ground, set a leveling rod on the plus or minus 1 mark or the top surface of the gantry plate, and read the back-view reading of 1.774m, so as to obtain the forward-view reading of 1.774+1.711-1.51 for the horizontal pile survey.

then stick the leveling rod on the groove wall and move it up and down until the horizontal line of sight of the leveling rod reads 1.974m, and hit a small stake on the groove wall along the bottom of the ruler, which is the horizontal pile to be laid out.

when building foundations are laid, the excavated geosynclines are deep pits, which are called foundation pits. If the foundation pit is too deep, and the elevation of the pit bottom cannot be directly measured by general methods, the hanging steel ruler can be used instead of the leveling ruler to transfer the ground elevation to the deep pit.

Extended data

There are many setting-out methods for site operation of construction setting-out; Generally, there are two kinds of setting-out methods: measuring and setting-out with the positioning ruler of the gantry plate and measuring and setting-out with the instrument. The former piles and sets up the gantry plate at a certain distance around the foundation of the building to be set-out, and draws a roughly right-angled line with the construction line on the gantry plate to tighten the line as much as possible.

then use the pythagorean theorem to combine the steel rule, and the size should be larger, generally 6, 8, and 11m, which is more accurate. First, measure the size on two control lines with a red pencil, then pull the ruler by two people, and one person can swing it to make any line fit the size of the steel rule stably. Then, fix the construction line on the gantry, check it again with the steel rule from the beginning, and hang the line and steel rule around after confirmation.

according to the axis size on the drawing, measure the setting point with a steel ruler, and hang it vertically on the ground, so that the excavation lines can be set separately with lime powder, and the elevation can be measured and set on the gantry plate with a level.

The latter is much simpler if you can use theodolite or total station. As long as you know the control points in the drawings or the control points determined on site, you can measure and determine the specific position of the axis according to the distance and angle relationship on the drawings.

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