Dynamic settlement in-situ dynamic test bench and test method for foundation soil

A dynamic settlement in-situ dynamic test method for foundation soil, comprising:

• step 1:
• setting the foundation soil with a width of 3 m and a length of 3 m in an in-situ test site;
• step 2:
• drilling a first column hole and a second column hole with a diameter of 20 mm and a depth of 10 m on a center line of foundation soil with a Luoyang shovel, wherein a distance between the first column hole and the second column hole is 1 m;
• step 3:
• wrapping sensors in remolded soil, cutting the sensors into soil columns, and preparing ten soil columns with the sensors in two groups;
• and placing a first soil column vertically at 10 m of each of the first column hole and the second column hole, backfilling soil to 8 m, then placing a second soil column vertically, backfilling soil to 6 m, and so on until the last sensor is placed;
• step 4:
• laying a first plastic waterproof film on a top of the foundation soil, arranging a vibration table and a loading system of a vibration load on the foundation soil, and arranging a waterproof film made of plastic film cloth between the vibration table foundation and the foundation soil;
• step 5:
• digging a trench with a width of 0.5 m, a length of 3 m and a depth of 10 m in the in-situ test site, specifically, the trench is excavated along the outer edge of the 3 m×3 m foundation soil set in step 1:
• two trenches are dug parallel to the 3 m-length side of the 3 m×3 m foundation soil (each trench is 3 m long, 0.5 m wide, 10 m deep), and two trenches are dug parallel to the 3 m-width side (each trench is also 3 m long, 0.5 m wide, 10 m deep), so that the trenches form a “frame” around the 3 m×3 m foundation soil;
• after excavation, the soil area enclosed by the trench frame is the remaining foundation soil, and since the total width/length of the original 3 m×3 m foundation soil minus the width of two opposite trenches (0.5 m×2=1 m) equals 2 m, the enclosed soil area forms a foundation soil column with a size of 2 m×2 m (depth consistent with the trench depth of 10 m), forming a foundation soil column with a size of 2 m*2 m, and laying a second plastic waterproof film on peripheries and bottoms of the foundation soil (i.e., the peripheries and bottom of the 2 m×2 m foundation soil column) and a trench wall (including the inner side walls and bottom of the excavated trench, ensuring the film is tightly attached to avoid gaps that cause water seepage or soil disturbance);
• step 6:
• performing a dynamic test for an undisturbed structural loess foundation under a state K0 by the above test facility, wherein the state K0, which is specifically defined as the ratio of lateral effective stress (denoted as σ′h, referring to the effective stress acting on the side surface of the 2 m×2 m foundation soil column formed in step 5, consistent with the lateral stress of the in-situ foundation soil) to vertical effective stress (denoted as σ′v, referring to the effective stress acting on the top surface of the 2 m×2 m foundation soil column, equal to the in-situ overburden stress of the foundation soil at the test site, i.e., the weight of the soil layer above the test soil column), and the mathematical expression is Ko=σ′h/σ′v;
• recording an acceleration response generated in a dynamic settlement process through a method of increasing an seismic wave amplitude step by step and by acceleration sensors and displacement sensors;
• and computing time history curves of accelerations of five points in a foundation according to the acceleration response and a displacement;
• step 7:
• changing a natural vibration frequency of vibration to obtain time history curves of velocities and time history curves of accelerations under different frequencies;
• and analyzing a relation between the accelerations and a period to obtain an acceleration response spectrum under an earthquake.