As the industrial and civil construction industry, a variety of complex and large-scale projects more and more buildings, engineering, building construction, changing the original state of the ground, and the foundation for building a certain amount of pressure applied, which is bound to cause deformation of the foundation and the surrounding strata. To ensure the building (structure) of the normal life of building materials and construction (structure) the safety of building materials and for future survey design and construction provide reliable information and the corresponding parameters of the settlement was built (structure) building materials necessary for settlement observation nature and importance of the increasingly evident. The existing standard also provides for high-rise buildings, tall structures, important historical buildings and continuous production facilities based on the basis of power equipment, landslides, subsidence monitoring Dengjun to conduct observations. High-rise buildings, particularly in the construction process, the application of settlement observation to enhance process monitoring, to guide reasonable construction processes occur in the construction process to prevent uneven settlement, and timely feedback for the survey design and construction department to provide detailed first-hand information, to avoid the settlement the main structure of the building caused the damage or impact on the structure using the function of the crack, causing great economic losses.

Observation of the implementation of the settlement

Working point and observation points, the layout of signs

Working basis points (hereinafter referred to as basis points) is the reference point for observing the settlement, the settlement should be based on engineering programs and cloth measuring network facilities requirements of the principle the establishment of settlement Shi test program should be based on the layout of the project features, on-site environmental conditions develop. Based on work experience, generally high-rise buildings should be laid around three basis points, and the building away from the range between 50m to 100m is appropriate. Point can make use of existing good stability point and the foot of a wall standard buried stone points, can also be the basis of stability in the region, the construction of the building a long time to set foot of a wall standard points. If the region does not have the above conditions, you can press the corresponding requirements, chosen as the pass is good for hiding and good, safe place to ensure the laying point. Laid by the starting point, before the facts in its stability, is strictly prohibited. Therefore, every time the elevation difference between the measured point to determine whether the relative stability between them, and point away from the building to meet regularly with high-grade standard of measurement points together in order to check the stability of the nuclear its own.


Settlement observation points should be based on the shape of the building, structure, geological conditions, pile type and other factors into account, laid in the most sensitive buildings in the settlement to reflect changes in location. Usually laid on the building corners, large amount of differential settlement location, geological conditions are obviously different sections, as well as settlement cracks on both sides. Note that observation points are laid and connected to solid buildings, making observation points change to reflect the genuine changes in the building. Graphic design in accordance with the building drawings cloth-point plan settlement observation points in order to determine the location of settlement observation points. In the operating point and settlement between the observation points of observation to establish a fixed route, and set up equipment to switch the point of the site and marked with the pile to ensure that the various observations are uniform along the route.




Settlement observed during testing cycle and Shi

Settlement observation period should reflect the laws of settlement and deformation of buildings, building (structure) building materials to the settlement, there are strict observation of time constraints, in particular, is the first observation to be on time, otherwise the settlement observation are not raw data, so that the observations are not comprehensive observational results. Other phases of re-measurement, the progress of the works to be carried out from time to time shall not be measured or tested additionally missed, the only way to get an accurate settlement of the situation or the law. Is generally believed that class built on sand soil on the building, its settlement during the construction period has been largely completed in the clay soil on the construction of buildings, its settlement during the construction period is only part of the settlement, therefore, the settlement cycle is changing. Accordance with the work experience in the construction phase, the frequency of observation should be a little bigger, generally based on 3 days, 7 days, 15 days to determine the observation period, or by number of storeys, the increase in load to determine observation period, observation period should be considered during construction of concrete foundation with the loading may be. Such as the suspension when the suspension and re-start when the time should be the observation time, in order to test suspension changes during the settlement of buildings, in order to re-start observations after the settlement of the way to judge whether the frequency should be adjusted based on. Upon completion, the observed frequency can be less, depending on the foundation soil type and the size of the settling velocity, generally a month, two months, three months, six months a year different cycles. Settlement is to enter the stable phase, by the settlement-time curves determined. Of key observations and scientific research projects, if the last three cycles observed in the weekly settlement period of not more than two times the measurement error, can be considered to have entered a stable phase. General engineering subsidence observations, if the velocity is less than 0.01 ~ 0.04mm / d, can be considered to enter the stable phase, the specific value should be based on various regions of the foundation soil compression set.


According to the settlement of the preparation of test programs and facilities to determine the observation period, the first observation should be solid after the observation points in a timely manner. High-rise buildings usually have one or several layers of underground structures, for the first time since the foundation began to be observed, in the basis of vertical and horizontal axis (edge-based Bureau) By design, the laying of good position in settlement observation points (temporary), temporary observation points to be a solid Well, before proceeding with the first observation. First observation of subsidence observation point elevation values are observed for the subsequent comparative basis, its precision is very high, Shi N2 level tends to be used when measuring precision leveling, and requires elevation of each observation point for the first time should be observed during the same period two second, compare observational results, if the same height difference between the observation points does not exceed ± 0.5mm, we can consider the first observation of the data is reliable. With the increase in the structure of each layer, temporary observation points and make observations to move the layer until the provisions of +0.00 and then laid a permanent observation points (for ease of observation may be permanent observation points are located at +500 mm), and then the construction of each layer of on the retest once, until its completion.


During the construction piling, excavation and infrastructure after the completion of the upper layers of the stages of the continual increase in settlement observation must be recorded each time observing the construction progress, an increase of loading capacity, warehouse import (export) cargo tonnage, the building tilted cracks the various effects of sedimentation changes and abnormal circumstances. Weekly observations, it should be timely to collate the observational data to calculate the amount of observation points of the settlement, differential settlement as well as the average settlement volume and velocity cycle. If there is change in the amount of abnormal, shall immediately notify the commission side, provide the basis for taking measures for preparedness, and appropriate increase in the number of observations.


Another person, different periods of observations should follow the "five-set" principle. The so-called "five-set", that is commonly referred to as settlement observation based on the reference point, point, and has been the object being observed on the settlement of observation points, point and should be stable; the instruments and equipment should be stable; observation of officers stability; observation of environmental conditions Basically, to be consistent; observation line, mirror position, procedures and methods to be fixed. The above measures can ensure the objective to minimize the subjective observation error uncertainty, so that the results measured with a uniform tendency; be able to ensure that all sub-retest results for the first time observed the comparability of the results of the same, so that the observed settlement a more realistic amount.

Settlement observation accuracy

According to the characteristics of the building and construction, design unit asked to choose the level of settlement observation precision. In no particular required in the circumstances, left the general structure of high-level building construction process, the use of second-class standard of measurement methods of observation will be able to meet the requirements of the settlement observations. The Observation requirements are as follows:


First, from poor, poor echo or ring closure: △ h = Σa-Σb ≤ 1.0, n said that the number of stations;


Second, the front and rear sight ≤ 30m;


Third, after-the-horizon difference ≤ 1.0m;


Fourth, the cumulative difference before and after-the-horizon ≤ 3.0m;


Fifth, the settlement after observation points relative to the point of view of the elevation difference tolerance: ≤ 1.0mm.