多点、宽频带、数字化系统在建筑工程中的应用

Application of An Multi Channel Wide Band Digital Strain Monitoring System on a Construction Site

一套在室内岩石力学实验中建立的多点、宽频带、数字化应变观测系统经过改造，被应用于大型工程的现场观测。该系统频带宽度为０～１００Ｈｚ，动态范围８０ｄｂ，可以同时记录上百点的载荷或变形的动态过程，自动建立观测数据库，并且提供动态回放分析功能及标准数据交换接口。在高层建筑深基坑支护体系的载荷监测中，应用该系统取得了一批数据，它们记录了土压力与支护系统之间相互作用的动态过程。观测结果表明，在深基坑周围的土压力分布很不均匀。在开挖过程中，支护体系的受力状态既存在与开挖深度相关的趋势性变化，也存在受温度影响的周期性日变，还有在特殊因素触发下产生的突变。应用表明，这一系统为施工的安全监测提供了新手段。

A multi channel wide band digital strain monitoring system has been built to monitor the dynamic process of strain field before unstable events of samples with different fault geometry in laboratory.The results show the relationship between the evolution of strain field and precursory field before instability. An in site monitoring system has been also developed in application of engineering project.Technical indexes of the system are as following:Width of frequencey:0～100Hz;Dynamic range:80db;Number of channels:1～128cha.Velocity of cycle check:0.1 sec～1h/cycle;Resolution:14 bit (1/16384);Rang of input sigual ±5V ;Distance for measuring:500m;Way of data storage:automatic data base establishing and output in text or graph file. Dynamic processes of the strain in a sustain system installed in a deep foundation tunnel has been monitored in the process of foundation excavation for a high building in Tian Jin. It is found that the lateral pressure from the slope appear some regularity: (1)The lateral pressure is increased with the depth of excavation. (2)The lateral pressures have daily periodic variation which amplitudes increase with the depth of excavation. (3)An anomaly increasing in strain record has been recognized before fracturing of a part of sustain system.An emergency measure has been taken to succeed in averting an accident. Application of multi channel wide band digital strain monitoring system proved that it is a new facility to ensure safety in construction.