(Seeking help) What are the purpose of soil sampling holes, SPT holes, and static probing holes in geological exploration reports? What aspect of geology is it measuring?

For soil sampling holes, there are those known as “control holes”; the soil samples from these holes are taken back for laboratory geotechnical tests. These differ from “identification holes”. Sonding holes are those created by standard penetration testing, while static probe holes are those resulting from static cone penetration testing. For the specific requirements regarding these tests and the results obtained, please refer to Chapter 10 on in-situ testing in the “Code for Geotechnical Investigation” GB 50021—2001

1. Geological reports are mainly divided into SPT boreholes and static probing boreholes, which use different mechanical equipment: the former employs a 63.5 kg standard drop weight to obtain soil samples in order to determine the bearing capacity of the foundation and the stratification of the soil, while the latter uses a geological drilling rig with a drill bit to acquire soil samples and generate stress profile curves. 2. Geotechnical tests are determined through laboratory tests on soil samples obtained from SPT holes. 3. Geological survey requires the application of the “three comparison” principle, namely SPT, static probing, and geotechnical tests, with comprehensive analysis to arrive at the results. ★Please refer to: 1. Both SPT holes and static penetration test holes are types of in-situ tests; the former uses a standard weight of 63.5 kg for vertical impacts, and the data from the last 30 cm of those impacts are used, after correction, to determine the bearing capacity of the foundation as well as to assess the density and degree of weathering of the sand. Static probing holes are drilled using geological drilling rigs and specialized equipment: static penetration testers and small static penetration instruments, which are mainly used for soft soil layers to obtain data such as stratification, classification, and bearing capacity based on the penetration ratio curves. 2. Due to limitations in domestic soil extraction equipment, technicians generally use in-situ measurement data. Last edited by Lailai on 2009-3-6 13:01]

What are the standard penetration test and static cone penetration test, respectively? What aspects of soil quality are being measured? Thank you

The standard penetration test (SPT) involves using a hammer with a mass of 63.4 kg, which falls freely along a drill pipe by a distance of 76 cm. A standard-sized penetration device is then driven down from the bottom of the hole by 15 cm, and an additional 30 cm is driven down as well; the number of blows required for this process is recorded (the standard penetration count). This value is used to determine the bearing capacity of the soil layer in question, as well as to assess the density of sandy soils and their susceptibility to liquefaction. The samples obtained from this test can be used in unconfined compressive strength tests as part of in-situ testing methods. The value of N from the standard penetration test can be directly plotted on the engineering geological profile, or a curve or histogram showing the relationship between the number of standard penetration blows N and depth for each borehole can be drawn. When calculating the average value of the statistical stratified SPT blows, outliers should be excluded. The Standard Penetration Test value of blows per unit length, N, can be used to evaluate the physical properties of sand, silt, and clay; soil strength, deformation parameters, foundation bearing capacity, and single-pile bearing capacity; liquefaction of sand and silt; and the feasibility of pile construction. Whether and how to make corrections when applying the N value should be determined based on the specific circumstances at the time the statistical relationship was established. The static cone penetration test (CPT) is an in-situ testing method in which a cone-shaped probe of specified dimensions is pressed uniformly into the soil layer under static pressure. The mechanical properties of the soil layer are evaluated based on the resistance encountered, thereby allowing for an indirect estimation of the bearing capacity and modulus of deformation at various depths within the soil layer, as well as for the classification of the soil layers. Based on the geometric characteristics of the penetration curve, together with data from adjacent boreholes and regional experience, soil layers are classified and soil types are determined ； Calculate the average values of the test data related to static cone penetration for each soil layer, or conduct statistical analysis on the data to determine the spatial variation patterns of the static cone penetration data. Based on static penetration data and utilizing regional experience, mechanical stratification can be carried out to estimate the plasticity state or density, strength, compressibility of soil, foundation bearing capacity, single-pile bearing capacity, pile driving resistance, and to determine liquefaction potential. The consolidation coefficient and permeability coefficient of soil can be estimated from the pore pressure decay curve.