Simple hydrological observation of borehole

In the process of drilling construction, simple hydrological observation is needed to understand the thickness, quantity, distribution and nature of aquifer in the work area, which can be used as supplementary data for special hydrological drilling and obtain necessary hydrogeological data for engineering design.

(1) Common instruments for borehole water level observation

The tools for observing dynamic water level or static water level usually use clocks or electric water level meters.

1. Method of observing water level with clock

As shown in Figure 3-2, when hanging the clock on a special hydrological rope (measuring rope) to measure the water level, first put the clock into the hole, and the bell mouth will make a noise when it touches the liquid level in the hole. At this point, read the value of the measuring rope at the fixed point of the orifice, which is the water level depth.

The method of observing water level with clock is often used to measure water level in vertical holes and shallow holes.

2. Using electronic water level gauge to observe water level.

As shown in Figure 3-3, the electric water level gauge consists of ammeter (or bulb), conductor, clock, contact (electrode) and float. When measuring, put the electric measuring clock into the hole. When the measuring clock touches the liquid level, the float rises to contact the contact. At this time, the circuit is connected, and at the same time, the ammeter pointer deflects or the bulb emits light, and the value on the wire is read, which is the depth of the water level in the borehole.

Figure 3-2 Water Level Clock

Figure 3-3 Schematic Diagram of Electronic Water Level Gauge

Electric water level meters are often used for water level observation in inclined holes and deep holes.

(2) Borehole return and final hole water level observation.

1. Observation requirements for drilling water level (i.e. dynamic water level)

Generally, it is measured once after tripping in and once before tripping in; The interval between two times shall not be less than 5 minutes. It is required to measure 1 ~ 2 times per shift at least. For example, the water level measured after tripping out is H 1, and the water level measured before tripping out is H2. If H 1 > H2, it means that the dynamic water level is rising; If H 1 < H2, it means that the dynamic water level is decreasing.

2. Observation requirements of final hole water level (i.e. static water level) in drilling.

Usually during the drilling stop time. The drilling stoppage time mainly means that when the airport stops drilling for more than two days for some reason, most of them need to observe the static water level, usually after the last hole is drilled. During observation, if the water level in the hole does not change much, it can be measured once per shift until the water level measured for the last 2 ~ 3 times is the same or the difference is not more than 2cm.

(3) Observe the consumption of flushing fluid and other contents during drilling.

1. Determination of flushing fluid consumption

During drilling, flushing fluid will continuously penetrate into permeable rock stratum, and the consumption of flushing fluid is called flushing fluid consumption. The consumption of flushing liquid per unit time is called water permeability.

Measuring the consumption of flushing fluid can preliminarily judge the water permeability and fracture development degree of rock stratum. According to the comprehensive borehole hydrological data, the horizon and depth of aquifer can also be determined, and the hydrogeological situation of borehole can be preliminarily evaluated.

Generally speaking, the measurement of consumption is to record the start time and scale of the normal circulation of flushing fluid after drilling, and then record the time and scale until the pump stops at the end of drilling.

Calculation formula of flushing liquid consumption:

Q=(Q 1+Q2)-Q3 (3- 1)

Where: Q is the consumption of washing liquid (L); Q 1 is the volume (l) of the original washing liquid; Q2 is the volume (L) of the added washing liquid; Q3 is the volume (L) of the rinsing liquid remaining in the water source tank.

2. Determination of borehole water inflow

In the process of drilling, if underground confined water is found to gush out or gush out from the orifice, the remaining feet on the machine should be measured immediately, and the hole depth and casing length when the water gushes out should be recorded. At the same time, stop drilling, lift drilling tools and observe water gushing. Its purpose is to know the buried depth, head height and water inflow of confined aquifer.

(1) Measurement of head height

The head height is the height at which the underground confined water gushes out of the surface and rises. According to the pressure of confined water, casing measurement, high pressure pipe measurement and pressure gauge measurement can be used.

(2) Measurement of water inflow

Water inflow is the amount of water that gushes out every second. The measurement methods of water inflow include container measurement, eruption height measurement and triangle weir box measurement.

3. Water temperature observation

In the process of drilling, when abnormal changes of water temperature in the hole are found, the water temperature should be observed in time. The purpose of observing borehole water temperature is to understand the physical properties of groundwater and delineate geothermal anomaly areas. Where there is geothermal reflection, the hole depth and water temperature changes of hot water should be recorded to accumulate data for geothermal research and development and utilization of geothermal resources in the future.

Thermometers and spring thermometers are often used to measure water temperature. For example, when groundwater flows to the orifice, it can be measured with an ordinary thermometer; If the water level is deep, it can be measured with a spring thermometer. If the water level in the borehole is deep, it needs to be measured by a slow thermometer with high pressure resistance.

4. Other content observation

In case of sudden water leakage in the broken zone and the hole during drilling, the hole depth should be recorded in detail; When drilling tools such as old holes and karst caves suddenly drop, the depth of starting and ending holes should be recorded; If gas escapes from the borehole, the depth of the escaped gas must be determined in time, and samples should be collected and sent to the laboratory for analysis and testing. Most gases are flammable, so attention should be paid to prevent fireworks to avoid accidents.

(4) Simple hydrological report records of drilling holes

1. Simple hydrological report content

The contents and formats of simple hydrological reports of drilling holes in all geological prospecting units in China are basically the same.

(1) Simple Hydrological Observation Report of Borehole

See Table 3-2 for the simple hydrological observation report of borehole.

Table 3-2 Simple Hydrological Observation Report of Borehole

(2) Observation report on drilling flushing fluid consumption

See Table 3-3 for the observation report of drilling flushing fluid consumption.

Table 3-3 Observation Report on Drilling Flushing Fluid Consumption

2. Simple hydrological report record requirements

1) The observation contents of each project shall be carried out according to the hydrogeological design requirements of the work area.

2) Observation must be carried out at the drilling site according to regulations, and be true, accurate, timely and neat, and filled in with a pen (or signature pen).