Engineering investigation units must comprehensively strengthen the management of site reconnaissance, survey outline compilation, original data collection and results data review, and be responsible for the quality of geological, seismic, hydrological, meteorological and other survey data provided. In recent years, due to the relaxation of quality management in some units and the simple pursuit of economic benefits, the quality of survey has declined or even been inferior, which has caused harm to engineering construction. Therefore, it is necessary to strengthen the total quality management of measurement work. According to my own work experience and lessons, the author thinks that the key link of process management must be grasped when strengthening the total quality management of geotechnical engineering investigation, and the three keys of prior guidance, intermediate inspection and finished product audit must be grasped when grasping process management.

2. About prior guidance

It is an important work to draw up the outline of survey work (hereinafter referred to as the outline), which is the main document to guide various professions (geology, surveying and mapping, drilling, in-situ testing, geotechnical testing, report writing, etc.). ) Work correctly. Therefore, compiling the outline is an important guarantee for the smooth progress of the whole investigation. The compilation of the survey outline is to formulate a survey action plan with high technical and economic benefits according to the engineering design intention and the geological conditions of the site, so that the main problems to be solved in this survey can be clearly defined ideologically before the survey work, so as to arrange the survey means and workload in a targeted manner and obtain the necessary information reflecting the macro-natural geological conditions for design and construction. In my opinion, in order to work out an outline that can really play a correct guiding role, we must choose the following management points: (1) According to the task requirements, carefully collect and study the existing survey data and architectural experience in the survey area and its vicinity. (2) Seriously study the technical requirements put forward by the design, thoroughly understand the design intent, and define the survey purpose and task; (3) Correct and reasonable determination of investigation methods and workload. These three points are interrelated. The first two points are the basis of choosing appropriate investigation methods and arranging investigation workload reasonably, which are the premise of high-quality investigation. Regarding the first point, such as the settlement calculation depth of Yangjiang high-rise building, when the compression layer is the upper and lower soil layers with low compressibility and high compressibility in the middle, it is generally 0.8- 1.0 times the foundation depth, and the control hole is 1.2 times the foundation width plus the foundation depth. However, if the compressibility of the upper soil layer is small and the compressibility of the lower soil layer is large, the calculated compression depth must reach 1.5 times of the foundation width, and the drilling depth and control hole depth should be 1.7 times of the foundation width plus the foundation buried depth. Generally, the hole depth requires the pile tip to enter the bearing stratum for 3-5m, and the natural foundation should be 1.5 times of the foundation width plus the foundation buried depth. Regarding the second point: If pile foundation is used in Yangjiang area, static sounding will be the main survey method, and the design parameters of pile foundation are mainly provided by static sounding results. If natural foundation is adopted, the number of cone penetration holes will be relatively reduced, while the number of soil holes will be relatively increased.

3. About the intermediate inspection

In the process of implementing any scheme, there are always places that are more or less inconsistent with the actual situation. Therefore, it is necessary to conduct an intermediate inspection of the whole process of scheme implementation. Through the intermediate inspection, we can find the problems existing in the implementation of the outline, modify and supplement the outline, and avoid major rework. Although the intermediate inspection is important, it is still a weak link, but it is usually not paid due attention to. The author believes that the intermediate inspection should focus on the following two points: (1) Check whether the measurement means and workload are appropriate and can meet the design needs. (2) Check whether the original basic scheme conforms to the actual situation.

There is a set of strata alluvial by Yangmo River in some areas of Yangjiang City. Due to the uplift of the earth's crust and the downward cutting of rivers, this sedimentary stratum is destroyed, and soft plastic cohesive soil with a thickness of several meters is often formed at a certain depth below the surface. The compressibility of this layer is only about 6.0MPa. In addition, due to the cutting action of running water in the later period, muddy soil with certain thickness and different sizes is distributed in the alluvial distribution area. If we don't know enough about the distribution characteristics of this stratum, it will lead to the fact that the measurement means and workload of contour survey are inconsistent with the actual situation, especially if there is no existing information about the survey point or nearby for reference.

Intermediate inspection can find problems and solve them in time. For example, the bearing layer (silt) at the pile end of a building is generally 6 meters thick, but it is only 2 meters in some sections, and the cohesive soil (medium compressibility) is below it. Considering the great difference in thickness, the depth of the pile tip in the bearing stratum has a great influence on the settlement rate of the building, the designer's opinions are solicited, and the isothickness line of the bearing stratum is made according to the design requirements, and some drilling holes are densified to 2m, which has achieved satisfactory results. Another example is the use of high-strength prestressed pipe piles in a building. During the intermediate inspection, it was found that there was a layer of soft plastic cohesive soil with a thickness of about 6m on the bearing layer, but a few holes were nearly 20m deep, which may be deep ditches by analysis. In order to provide the name of the pile accurately, we made a hole filling. It was confirmed by hole filling that there was a deep ditch several meters wide in this section, which was later confirmed by piling. For another example, in a project, Party A originally planned to set up a basement in the main building of 14 floor, and there was no basement in another 7-storey commercial and residential building. During the mid-term inspection before the preparation of the survey report, it was found that the geological conditions were very unfavorable to the basement of 14 floor, because to dig the confined aquifer, support and precipitation were needed, and the cost would be high and the construction period would be long. On the other hand, the 7-story commercial and residential building site has deposited hard cohesive soil with a thickness of more than 7m due to later running water cutting, and the basement on the first floor will not be affected by confined water. Therefore, we suggest that it should have been located on the 14 floor of the main building.

It can be seen that intermediate inspection should be done consciously in engineering practice, especially for large-scale projects and sites with complex geological conditions. For example, the project leader will draw and analyze the geological profile in time, get in touch with the technical leader, designer and Party A in time, and adjust the survey means and workload as needed.

4, about the finished product review

The proofreading of finished products must focus on the following points: (1) Whether the stratigraphic division is accurate; (2) Whether the division principle of engineering geology is correct and whether the division accuracy meets the design requirements. (3) Whether the proposed design parameters are accurate and reliable. (4) Whether the conclusion is clear and correct. (5) Whether the proposal is reasonable and feasible and whether the basis is sufficient.

Due to the different technical level and sense of responsibility of the project leaders, there are more or less the above problems in the survey products, especially in large-scale projects or projects with complex geological conditions. Some soil layers with the same soil properties but different indexes are classified as the same layer. For example, the bearing layer at the pile end of a project is silty sand, and its qc is generally above 10 MPa, but a borehole is only 5MPa, which belongs to the same layer during investigation. When testing piles, just one pile is selected under the qc of 5MPa, and its RK is lower than other test piles. Although some have engineering geological zoning, they do not explain the principles and basis of zoning, which makes it impossible to judge the reliability and accuracy of zoning; Some reports have vague conclusions. If there is 1-3m soft plastic silty clay on the site hard plastic clay, the conclusion of a 6-story residential building is that "the site soil is evenly distributed and the geology is good". Obviously, soft plastic silty clay cannot be defined as good soil. For example, the conclusion is changed to "soft plastic silty clay is poor in soil quality and uneven in thickness, so it is not suitable for foundation bearing layer, and hard plastic silty clay is good in soil quality. Some reports have ambiguous conclusions, such as "possible liquefaction" and "possible landslide", which makes designers at a loss; Some reports have conclusions and suggestions, but the arguments are insufficient, and so on.

The key to proofreading finished products is the principle of proofreader. Problems and mistakes in finished products should be clearly pointed out, and traces should be left in the proofreading form. The report writer can reserve different opinions and leave traces, but it must be revised according to the highest audit opinion.