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摘   要

地基的強(qiáng)夯法作為一種對(duì)非飽和土夯實(shí)有利的沖擊荷載，是當(dāng)今應(yīng)用于工程上的主流地基壓實(shí)方法，具有方便、快捷、經(jīng)濟(jì)等特點(diǎn)，但是由于非飽和土的結(jié)構(gòu)不規(guī)律、應(yīng)力復(fù)雜等特性，至今沒有一套完善、有效的理論及規(guī)范來指導(dǎo)施工，依然以經(jīng)驗(yàn)為主，故強(qiáng)夯機(jī)理以及技術(shù)的發(fā)展與改進(jìn)仍需進(jìn)一步的完善。本實(shí)驗(yàn)通過強(qiáng)夯法模型試驗(yàn)，研究非飽和土在沖擊荷載下的力學(xué)響應(yīng)和參數(shù)變化，為強(qiáng)夯法理論的進(jìn)步與完善提供一定的參考。

本實(shí)驗(yàn)利用落錘、動(dòng)態(tài)測(cè)試儀和土壓力盒等工具，對(duì)非飽和土進(jìn)行沖擊加載并對(duì)動(dòng)應(yīng)力測(cè)量，得到土體應(yīng)力隨深度的分布曲線，以分析動(dòng)應(yīng)力在豎直方向和水平方向的分布和傳播規(guī)律；同時(shí)也測(cè)量夯坑深度和寬度以及沖擊前后土體參數(shù)的變化，來研究沖擊載荷下非飽和土的受力特征。

研究發(fā)現(xiàn)：（1）在沖擊荷載作用下，土體應(yīng)力隨土體深度增加而減小，且應(yīng)力波的波峰持續(xù)時(shí)間很短，但應(yīng)力值在衰減結(jié)束時(shí)不為零；（2）在沖擊載荷作用下，含水率降低、孔隙比變小、飽和度提高，而密度在近夯擊點(diǎn)附近增加較多，遠(yuǎn)離夯擊點(diǎn)增加較少；（3）土體的水平和豎直方向的變形隨著夯擊次數(shù)的增加趨于穩(wěn)定，最終會(huì)達(dá)到一個(gè)臨界值；（4）隨著深度的增加，沖擊的影響在逐漸減弱；豎直方向動(dòng)應(yīng)力主要作用在淺層區(qū)域，且越靠近沖擊點(diǎn)衰減越快；隨著沖擊次數(shù)的增多，動(dòng)應(yīng)力先是持續(xù)增強(qiáng)，當(dāng)達(dá)到一定沖擊次數(shù)時(shí)動(dòng)應(yīng)力增長(zhǎng)逐漸減慢，最后基本一致。

關(guān)鍵詞：非飽和土，沖擊荷載，土體應(yīng)力，土體參數(shù) 

Abstract

Foundation of dynamic compaction method as a of unsaturated compacted soil beneficial impact load, is today's application in engineering of mainstream foundation compaction method, with convenient, fast, economic and other characteristics, but due to the unsaturated soil structure is irregular, complex features force. So far, there is no a set of perfect and effective method and standard to guide the construction, still to experience based, so strong tamping mechanism and technology development and improvement still need further improvement. In this experiment, the mechanical response and parameters of unsaturated soil under impact load were studied by means of dynamic compaction test, which provided reference for the improvement and improvement of dynamic compaction method.

This experiment use hammer, dynamic testing instrument and soil pressure box tool, for unsaturated soil impact loading and the dynamic force measurement, got the soil stress distribution curve with depth, in order to analyze the dynamic stress in the vertical direction and the horizontal direction distribution and propagation rules; also measured tamping pit depth and width as well as the impact of changes in soil parameters and to study the stress characteristics of saturated soil non under impact load.

The study found that: (1) under the impact load, the soil stress decreases with the increase of soil depth, and the stress wave of very short duration, but the stress value is not zero in attenuation at the end; (2) under impact load, reducing the moisture content, void ratio, saturation decreases the degree of increase, while the density near the tamping point near the more far away from the tamping point increased less; (3) the horizontal and vertical direction of soil deformation with increasing compaction number tends to be stable, will eventually reach a critical value; (4) with the increase of depth, the impact of the effect is gradually weakened; the vertical dynamic stress of the main role in the shallow area, which is closer to the point of impact attenuation increases; with the increase of impact times, the dynamic stress is strengthened continuously, when reaching a certain number of impact when the dynamic stress growth gradually slowed down, finally consistent.

Key Words ：Unsaturated soil, Impact load, Soil stress, Soil parameters.